Chapter 18: Lifespan Nutrition

Human bodies change significantly over time, and food is the fuel for those changes. Although people of all ages need the same nutrients — carbohydrates, essential fatty acids, amino acids, vitamins, minerals, and water — the amounts differ. We will discuss nutrient needs during these life stages:

• Pregnancy: The development of a fertilized egg into a zygote, an embryo, and then into a fetus in preparation for birth.
• Infancy: From birth to the first birthday.
• Toddler years: Ages one, two and three years.
• Childhood. Ages four to eight years.
• Puberty. Ages nine through thirteen, also called early adolescence.
• Older adolescence. Ages fourteen through eighteen.
• Adulthood. Age nineteen to the end of life. Subdivided into young (19-30), middle (31-50), and older (51+) adulthood.

Pregnancy

Pregnancy is a developmental marathon of about forty weeks. It is divided into three trimesters: the first is weeks one to twelve, the second trimester is weeks thirteen to twenty-seven, the third is weeks twenty-eight to birth. At conception, a sperm cell fertilizes an egg cell, creating a zygote. The zygote rapidly divides into multiple cells to become an embryo. Approximately two weeks after fertilization, the embryo implants in the uterine wall. Further development and growth in the uterus result in a fetus. At approximately eight weeks, nerve cells branch to form neural pathways. The heart begins beating at five to six weeks. An ultrasound examination in the second trimester may reveal growth or developmental anomalies. At twenty-eight weeks, the unborn baby begins to add body fat in preparation for life outside of the womb.^[1]

A pregnant woman’s nutritional choices affect her own health as well as that of the fetus. Poor maternal nutrition can lead to low birth weight (less than 5.5 pounds or 2,500 grams) and other developmental problems.

For medical purposes, pregnancy is measured from the first day of the last menstrual period until childbirth, and typically lasts about forty weeks. Major changes occur in the earliest days, often before a woman is aware of the pregnancy. During this period, adequate nutrition supports cell division, tissue differentiation, and organ development. As each week passes, new milestones are reached. Therefore, individuals who are trying to conceive should make proper dietary choices to ensure the delivery of a healthy baby.

Folate

Women of childbearing age who may become pregnant should intake 400 mcg of folate per day prior to pregnancy and 600 mcg per day during pregnancy. Folate is crucial for synthesis of nucleotides for the DNA necessary for cell division. A deficiency can cause megaloblastic anemia, or the development of abnormal red blood cells, in pregnant women. It can also impact the fetus. Inadequate folic acid increases the risk of a specific type of birth defect: neural tube defects. When the tube containing the spinal column fails to close, a baby may be born with spina bifida, a condition which may lead to lifelong paralysis of the legs and absence of bowel and bladder control. Adequate folate in the mother’s body during the first eight weeks of pregnancy lowers the risk for neural tube defects. Therefore, it is a public health priority to educate all potential mothers about the importance of adequate folate.

Weight Gain during Pregnancy

Appropriate weight gain is necessary for healthy fetal development as well as maternal health. Infant birth weight is one of the best indicators of a baby’s future health. Mothers of healthy pre-pregnancy weight should gain between 25 and 35 pounds during the pregnancy.

Table 18.1 Body Mass Index and Pregnancy. Source: Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: The National Academies Press, 2009. Used under fair use guidelines.

Pre-pregnancy BMI	Weight Category	Recommended Weight Gain
Below 18.5	Underweight	28–40 lbs.
18.5–24.9	Normal	25–35 lbs.
25.0–29.9	Overweight	15–25 lbs.
Above 30.0	Obese (all classes)	11–20 lbs.

Starting weight below or above the normal range can lead to complications. Those with a pre-pregnancy BMI below twenty are at a higher risk of a preterm delivery and an underweight infant. Mothers with a pre-pregnancy BMI above thirty have an increased risk of the need for a cesarean (surgical) delivery.

As a rule, it is healthy for a pregnant woman to gain 2 to 5 pounds in the first trimester. Weight gain of one pound per week during weeks 13 to delivery is a general recommendation. Some of the new weight is fetal growth; more is due to changes in the body that support the pregnancy. Areas of weight gain are shown in Figure 18.2.

Some of the weight gained in pregnancy is lost at delivery. The new parent will continue to shed weight as they lose accumulated fluids and blood volume returns to normal. Some studies show that breastfeeding may help with weight loss.^[2] The gain of a healthy amount of weight and participation in regular physical activity during pregnancy may lead to easier weight loss post-pregnancy. Many who gain large amounts of weight during pregnancy have a hard time losing it after delivery.

Energy and Macronutrients

During the first trimester, the energy requirements are unchanged. However, as the pregnancy progresses, caloric intake should increase. This is partly due to an increase in metabolism, which rises during pregnancy and contributes to increased energy needs. Carbohydrate needs will also increase as will the need for protein. These macronutrients help to build the placenta, supply energy for the growth of the unborn baby, and supply amino acids for protein synthesis for building new tissues in mother and fetus.

Table 18.2 Typical Energy and Macronutrient Needs During Pregnancy for Females Aged 19-30 years. Source: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press, 2005. Used under fair use guidelines.

Need	Nonpregnant	Pregnant
EER, kcal/d (for 19y)	2403	+340 (2nd trimester), +452 (3rd trimester)
Carbohydrates, RDA g/d	130	175
Protein, RDA g/d	46	71

There are no specific recommendations for fats in pregnancy. However, increasing intake of essential fatty acids linoleic acid and ∝-linolenic acid is recommended because they are incorporated into the placenta and fetal tissues.  Very low-fat diets are not recommended because they do not contain enough essential fatty acids and fat-soluble vitamins. Fatty acids are important during pregnancy because they support the baby’s brain and eye development.

Micronutrients

The daily requirements micronutrients change with the onset of a pregnancy. Taking a daily prenatal supplement or multivitamin helps to meet these needs, but most of these requirements can be met with a healthy, varied diet. The following table compares the normal levels of required vitamins and minerals to the levels needed during pregnancy.

Table 18.3 Recommended Micronutrient Intakes During Pregnancy for Females Aged 19-30 years. Source: Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press, 2011. Used under fair use guidelines.

Nutrient	Nonpregnant	Pregnant
Vitamin A (µg/d)	700	770
Thiamine (B1) (mg/d)	1.1	1.4
Riboflavin (B2) (mg/d)	1.1	1.4
Niacin (B3) (mg as NE/d)	14	18
Vitamin B6 (mg/d)	1.5	1.9
Folate (µg/d)	400	600
Vitamin B12 (µg/d)	2.4	2.6
Vitamin C (mg/d)	75	85
Vitamin D (µg/d)	15	15
Vitamin E (mg/d)	15	15
Calcium (mg/d)	1,000	1,000
Iron (mg/d)	18	27
Magnesium (mg/d)	310	350
Phosphorus(mg/d)	700	700
Zinc (mg/dg)	8	11

The micronutrients involved with building the skeleton—vitamin D, calcium, phosphorus, and magnesium—are crucial during pregnancy to support fetal bone development. Although the levels are unchanged with pregnancy, many adults do not consume adequate amounts and should make an extra effort to meet those needs.

There is an increased need for all B vitamins during pregnancy. Adequate vitamin B6 supports the metabolism of amino acids, while more vitamin B12 is needed for the synthesis of red blood cells and DNA. Additional zinc is crucial for cell development and protein synthesis. The need for vitamin A also increases, and extra iron intake is important because of the increase in blood supply during pregnancy and to support the fetus and placenta. Iron is the one micronutrient that is almost impossible to obtain in adequate amounts from food sources only. Therefore, even with a healthy diet, there still is a need to take an iron supplement, usually in the form of ferrous salts. Also remember that folate needs increase during pregnancy to 600 micrograms per day to prevent neural tube defects and to produce the extra blood cells a body requires during pregnancy.

For most other minerals, recommended intakes are like those for nonpregnant individuals, although it is crucial to meet the RDAs to reduce the risk of birth defects. Taking megadose supplements can lead to excessive amounts of certain micronutrients, such as vitamin A and zinc, which may produce toxic effects that can also result in birth defects.

Eating during Pregnancy

To accommodate the increased macronutrient and micronutrient needs, nutrient-dense foods, which are higher in proportion of macronutrients and micronutrients relative to calories, are recommended. Examples of nutrient-dense foods include fruits, vegetables, whole grains, peas, beans, reduced-fat dairy, and lean meats. Pregnant women should be able to meet almost all their increased needs via a healthy diet. However, expectant mothers and their healthcare providers discuss prenatal supplements to ensure an adequate intake of hard-to-obtain nutrients including iron and folate. Here are some additional dietary guidelines for pregnant women^[3]:

Pregnant people should increase their intake of iron, calcium, folic acid, vitamin A, and vitamin B₁₂. Some of these needs can be met via increased food intake, which also provides extra kilocalories necessary during pregnancy. Supplements are also useful here, so long as tolerable upper limits are minded.

Eat a well-balanced diet, including fruits, vegetables, whole grains, calcium-rich foods, lean meats, and a variety of cooked seafood (excluding fish that are high in mercury, such as swordfish and shark).

Drink additional fluids, especially water.

Alcohol can harm a growing fetus. Women are encouraged to avoid alcohol before and during the pregnancy to avoid a range of abnormalities included in Fetal Alcohol Syndrome (FAS). Possible effects of alcohol on a fetus include learning and attention deficits, heart defects, and abnormal facial features (See Figure 18.3). Alcohol can slow fetal growth, damage the brain, or even result in miscarriage.

Caffeine intake may affect a fetus. Caffeine is found in coffee, tea, cola, cocoa, chocolate, and some over-the-counter painkillers. Very high amounts of caffeine have been linked to babies born with low birth weights. A report in the American Journal of Obstetrics and Gynecology found an increased risk of miscarriage in women consuming over 200 milligrams of caffeine daily (approximately the amount in 16 ounces of coffee or 32 ounces of tea).^[4] Many experts have agreed that small amounts of caffeine each day are safe (about one 8-ounce cup of coffee a day or less).^[5]

Foodborne illness can cause health problems during pregnancy. For example, the foodborne illness caused by the bacteria Listeria monocytogenes can cause spontaneous abortion and fetal or newborn meningitis. According to the CDC, those pregnant are twenty times more likely to become infected with this disease, which is known as listeriosis, than nonpregnant, healthy adults. Symptoms include headaches, muscle aches, nausea, vomiting, and fever. If the infection spreads to the nervous system, it can result in a stiff neck, convulsions, or a feeling of disorientation.^[6]

Foods likely to contain bacteria should be avoided: unpasteurized dairy products, especially soft cheeses, smoked seafood, hot dogs, paté, cold cuts, and uncooked meats.

References

1. Polan EU, Taylor DR. Journey Across the LifeSpan: Human Development and Health Promotion. Philadelphia: F.A. Davis Company; 2003, 81–82.
2. Stuebe AM, Rich-Edwards JW. The Reset Hypothesis: Lactation and Maternal Metabolism. Am J Perinatol. 2009; 26(1), 81–88. https://doi.org/10.1055/s-0028-1103034.
3. Staying Healthy and Safe. US Department of Health and Human Services, Office on Women’s Health. https://womenshealth.gov/pregnancy/youre-pregnant-now-what/staying-healthy-and-safe. Updated September 26, 2025. Accessed March 4, 2026.
4. Weng X, Odouli R, Li DK. Maternal caffeine consumption during pregnancy and the risk of miscarriage: a prospective cohort study. Am J Obstet Gynecol 2008;198, 279.e1-279.e8. https://doi.org/10.1016/j.ajog.2007.10.803.
5. American Medical Association. Complete Guide to Prevention and Wellness. Hoboken: John Wiley & sons, Inc.; 2008, 495.
6. Listeria in Pregnancy – Risks, Treatment, and Prevention. American Pregnancy Association. N.D. https://americanpregnancy.org/healthy-pregnancy/pregnancy-concerns/listeria-during-pregnancy/. Accessed September 1, 2025. 

Lactation

After birth, healthy eating by the mother is important to her recovery and health. If she is able and chooses to breastfeed, the mother’s nutrition also impacts the production and quality of breastmilk for the infant. Breastmilk contains all six types of nutrients in the appropriate amounts for a newborn’s rapid growth and development. The World Health Organization (WHO) recommends that infants be breastfed exclusively for the first six months. Breastfeeding is not always feasible; if not, high-quality infant formulas are the best substitute. Around the world, less than 40 percent of infants under the age of six months are breastfed exclusively.^[1]

Lactation is the synthesis and secretion of breast milk. Early in pregnancy, mammary glands prepare for milk production. Hormones including prolactin stimulate the growth of the milk duct system. Pregnancy hormones progesterone and estrogen drop rapidly after delivery, which stimulates to production of milk. Hormonal regulation of lactation is complex; the hormone oxytocin rises when an infant suckles, promoting milk release, which is known as the milk ejection reflex.^[2]

Extra calories and fluid are needed to make breastmilk: 500 additional calories during the first six months of lactation and 400 additional calories during the second six months. The energy needed to support breastfeeding comes from both increased intake and from stored fat. During the first six months, 330 calories may come from increased intake and 170 calories from fat stores. This helps explain why breastfeeding may promote weight loss. Lactating women should drink 3.1 liters of liquids per day (about 13 cups) to maintain milk production, according to recommendations. Table 18.4 shows how nutrient needs increase during lactation.

Table 18.4 Recommended Nutrient Intakes for Females aged 19-30y During Lactation. Source: Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press, 2011. Used under fair use guidelines.

Nutrient	Nonpregnant Females	Lactating Females
Vitamin A (µg)	700	1,300
Thiamine (B1) (mg)	1.1	1.4
Riboflavin (B2) (mg)	1.1	1.6
Niacin (B3) (mg)	14	17
Vitamin B6 (mg)	1.3	2.0
Folate (µg)	400	500
Vitamin B12 (µg)	2.4	2.8
Vitamin C (mg)	75	120
Vitamin D (µg)	15	15
Vitamin E (mg)	15	19
Calcium (mg)	1,000	1,000
Iron (mg)	18	9
Magnesium (mg)	310	310
Phosphorus	700	700
Zinc (mg)	8	12

Diet can impact milk production and quality. Lactating mothers should avoid illegal substances and cigarettes. Some legal drugs and herbal products can be harmful as well, so it is helpful to discuss them with a health-care provider. Mothers may discover that certain food upset the stomachs of their infants. Lactating women who wish to drink alcohol should discuss it with their healthcare provider. There is no defined safe amount of alcohol during breastfeeding, but imbibing up to one standard drink (e.g. a 12 oz. beer or a 5 oz. glass of wine) is not known to harm a baby.^[3]

References

1. Breastfeeding. World Health Organization. https://www.who.int/news-room/facts-in-pictures/detail/breastfeeding. Updated February 20, 2018. Accessed September 5, 2025.
2. King J. Contraception and Lactation: Physiology of Lactation. Journal of Midwifery and Women’s Health. 2007; 52(6), 614–20. https://doi.org/10.1016/j.jmwh.2007.08.012
3. Harms R. Breast-Feeding and Alcohol: Is It Okay to Drink? Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/expert-answers/breast-feeding-and-alcohol/faq-20057985. Updated April 26, 2024. Accessed March 4, 2026.

Infancy (The First Year)

Many physiological changes occur during infancy. The trunk of the body grows faster than the arms and legs, while the head becomes less prominent in comparison to the limbs. Organs and organ systems grow rapidly. Countless new synapses form to link brain neurons. Fontanels, the “soft spots” on a newborn’s skull, allow the skull to accommodate rapid brain growth. The posterior fontanel closes by the age of eight weeks. The anterior fontanel closes about a year later. Developmental milestones include sitting up without support, learning to walk, teething, and vocalizing and many others. Adequate nutrition is important for these changes.^[1]

During the first year, an infant’s height increases by 50 percent, while weight triples. Other important developmental measurements include head circumference and weight. Health professionals use growth charts to track growth compared to standard measurements for an infant’s age (Figure 18.4). Growth charts may provide warnings that a child has a medical problem or is malnourished. Insufficient weight or height gain during infancy may indicate a condition known as failure-to-thrive (FTT), which is characterized by poor growth. FTT can occur at any age, but in infancy, it typically occurs after six months. Some causes include poverty, insufficient food intake, feeding inappropriate foods, and excessive intake of fruit juice.

Energy and Macronutrients

Energy needs relative to size are greater for infants than for adults. A baby’s resting metabolic rate is two times that of an adult. The RDA to meet energy needs changes as an infant grows. The IOM uses a set of equations to calculate the total energy expenditure and resulting energy needs. For example, the equation for the first three months of life is (89 x weight [kg] −100) + 175 kcal.

The estimated energy requirement for infants from zero to six months of age is 472 to 645 kilocalories per day for boys and 438 to 593 kilocalories per day for girls. For infants ages six to twelve months, the estimated requirement is 645 to 844 kilocalories per day for boys and 593 to 768 kilocalories per day for girls. From the age one to age two, the estimated requirement rises to 844–1,050 kilocalories per day for boys and 768–997 kilocalories per day for girls.^[2] How often an infant wants to eat changes over time due to growth spurts, which typically occur at about two weeks and six weeks of age, and again at about three months and six months of age.

The dietary recommendations for infants are based on the nutritional content of human breast milk. Carbohydrates are 45 to 65 percent of the caloric content in breast milk; the RDA for carbohydrates is 130 grams. Most carbohydrate in human milk is lactose, which infants digest and tolerate well. In fact, lactose intolerance is practically nonexistent in infants. Protein makes up 5 to 20 percent of the caloric content of breast milk, which amounts to 13 grams per day. Infants have a high need for protein to support growth and development, though excess protein (which is only a concern with bottle-feeding) can cause dehydration, diarrhea, fever, and acidosis in premature infants. The remaining 30 to 40 percent of the caloric content in breast milk comes from fat. A high-fat diet is necessary to encourage the development of neural pathways in the brain and other parts of the body. However, saturated fats and trans fatty acids inhibit this growth. Infants over the age of six months and no longer exclusively breastfed, should not consume foods high in these types of fats.

Micronutrients

Almost all the nutrients that infants require are met by an adequate amount of breast milk. There are a few exceptions, though. Human milk is low in vitamin D, which is needed for calcium absorption and building bone, among other things. Therefore, breastfed children often take a vitamin D supplement in the form of drops. Infants at the highest risk for vitamin D deficiency are those with darker skin and no exposure to sunlight. Breast milk is also low in vitamin K, which is required for blood clotting, and deficits could lead to bleeding or hemorrhagic disease. Babies are born with limited vitamin K; the American Academy of Pediatrics recommends a single shot of vitamin K at birth. In addition, breast milk is not high in iron, but the iron in breast milk is well absorbed by infants. After four to six months, an infant needs an additional source of iron other than breast milk.

Infants have a high need for fluids, 1.5 milliliters per kilocalorie consumed compared to 1.0 milliliters per kilocalorie consumed for adults. Children have larger body surface area per unit of body weight and a reduced capacity for perspiration. Therefore, they are at greater risk of dehydration. However, parents or other caregivers can meet an infant’s fluid needs with breast milk or formula. As solids are introduced, parents must make sure that young children continue to drink fluids throughout the day.

Components of Breast Milk

Colostrum is produced immediately after birth, prior to the start of milk production, and lasts for several days after the arrival of the baby. Colostrum is thicker than breast milk and is yellowish or creamy in color. This protein-rich liquid fulfills an infant’s nutrient needs during early days. Although low in volume, colostrum is a concentrated source of fat-soluble vitamins, minerals, and immunoglobulins (antibodies) that pass from the mother to the baby. Immunoglobulins provide passive immunity for the newborn and protect the baby from some bacterial and viral diseases. Two to four days after birth, colostrum is replaced by transitional milk. Transitional milk lasts for approximately two weeks and includes high levels of fat, lactose, and water-soluble vitamins. It also contains more calories than colostrum. The last stage of breast milk is mature milk. Two types of mature milk appear during a feeding. Fore-milk occurs at the beginning of a feeding and includes water, vitamins, and protein. Hind-milk occurs after the initial release of milk and contains higher levels of fat, which is necessary for weight gain. Combined, these ensure that a baby receives adequate nutrients to grow and develop properly.^[3]

About 90 percent of mature milk is water, which helps an infant remain hydrated. The other 10 percent contains carbohydrates, proteins, and fats, for energy and growth. Like cow’s milk, the main carbohydrate of mature breast milk is lactose. Breast milk contains vital fatty acids, such as docosahexaenoic acid (DHA) and arachidonic acid (ARA). In terms of protein, breast milk contains more whey proteins than casein (which is the reverse of cow’s milk). Whey proteins are easier for infants to digest. Breast milk also contains lactoferrin, an iron-gathering compound that helps iron absorption in the infant’s intestines. Together, they are a complete protein source, which means they contain all the essential amino acids.

Breast milk provides adequate vitamins and minerals. Although absolute amounts of some micronutrients are low, they are more efficiently absorbed by infants. Human milk also provides hormones and growth factors to help a newborn develop. Milk even contains digestive enzymes (amylase, lipase) that help a baby digest breast milk!

Bottle-Feeding

Some parents are unable to breastfeed or choose to bottle-feed. Various types of infant formulas are available. Standard formulas use cow’s milk as a base. They have 20 calories per fluid ounce, like breast milk, with vitamins and minerals added. Soy-based formulas may be given to infants who develop diarrhea, constipation, vomiting, colic, or abdominal pain, or to infants with a cow’s milk protein allergy. Hypoallergenic protein hydrolysate formulas may be given to infants who are allergic to cow’s milk and soy protein. This type of formula uses hydrolyzed protein, meaning that the protein is broken down into amino acids and small peptides, which makes it easier to digest. Preterm infant formulas are given to low-birth-weight infants if breast milk is unavailable. Preterm infant formulas have 24 calories per fluid ounce and are given until the infant reaches a desired weight. Most babies need about 2.5 ounces of formula per pound of body weight each day. Therefore, the average infant should consume about 24 fluid ounces of breast milk or formula per day.

Introducing Solid Foods

Infants should be breastfed or bottle-fed exclusively for the first six months of life according to the WHO. The American Academy of Pediatrics recommends exclusive breast feeding for six months, and until either 2 years of age or mutual desire by mother and infant to stop. Bottle feeding should be done with only breast milk or formula.^[4] Infants should not consume solid foods prior to six months as it may make them less hungry for milk or formula. If that occurs, an infant may not consume the right quantities of nutrients. If parents try to feed an infant who is too young or is not ready, their tongue will push the food out, the extrusion reflex. After six months, the suck-swallow reflexes are not as strong, and infants can hold up their heads and move them around, which make eating solid foods more feasible.

Solid baby foods can be bought commercially or prepared from regular food using a food processor, blender, food mill, or grinder at home. By nine months to a year, infants can chew soft foods and can eat solids that are well chopped or mashed. Parents should introduce one new food at a time, to help identify allergies or food intolerances. An iron supplement is also recommended at this time.

References

1. McMillan B. Illustrated Atlas of the Human Body. Sydney, Australia: Weldon Owen. 2008, 248.
2. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2005. Washington, D.C.: The National Academies Press. 2005, 169–70. https://doi.org/10.17226/10490.
3. Breastfeeding: Overview.  American Pregnancy Association. https://americanpregnancy.org/healthy-pregnancy/breastfeeding/breastfeeding-overview/. N.d. Accessed September 5, 2025.
4. Infant food and feeding. American Academy of Pediatrics. https://www.aap.org/en/patient-care/healthy-active-living-for-families/infant-food-and-feeding/. Updated November 28, 2023. Accessed March 4, 2026.

Toddler Years (1-3 years old)

Major physiological changes occur in the toddler years. The limbs grow faster than the trunk, which gives the body more adult-like proportions. By the end of the third year, a toddler is taller and more slender with a more erect posture. Bone density increases and bone tissue gradually replaces cartilage. This process, ossification, is not completed until puberty.^[1]

Developmental milestones include running, drawing, toilet training, and self-feeding. How a toddler acts, speaks, learns, and eats offers important clues about their development. Their physical growth and motor development slows compared to infancy. However, toddlers experience enormous intellectual, emotional, and social changes. Food and nutrition continue to play an important role in a child’s development. During this stage, the diet shifts from breastfeeding or bottle-feeding to solid foods and other liquids. Parents of toddlers remain aware of the risk of dehydration as toddlers’ fluid requirements remain high. Children learn how to eat on their own and develop personal preferences. With the proper diet and guidance, toddlers can continue to grow and develop at a healthy rate.

Nutritional Requirements

A toddler’s serving sizes should be approximately one-quarter those of an adult, though individual needs (plus a toddler’s level of cooperation on a given day) will vary.^[2] One way to estimate serving sizes for young children is one tablespoon for each year of life. For example, a two-year-old child would be served 2 tablespoons of fruits or vegetables at a meal, while a four-year-old would be given 4 tablespoons, or a quarter cup. Here is an example of a toddler-sized meal:

1. 1 ounce of meat or chicken, or ¼ cup of beans
2. One-quarter slice of whole-grain bread
3. 2 tablespoons of cooked vegetable
4. 2 tablespoons of fruit

Energy

Energy requirements for ages two to three are 1,000 to 1,400 calories a day. In general, a toddler needs to consume about 40 calories for every inch of height. For example, a young child who measures 32 inches should take in an average of 1,300 calories a day. The recommended caloric intake also varies with activity level. Toddlers require small, frequent, nutritious snacks and meals to satisfy energy requirements.

Table 18.5 Serving Sizes for A Two-year-old. Note that 1 ounce = 28 grams. Source: Nutrition Guide for Toddlers | Nemours KidsHealth. Reviewed April 2025. Accessed May 24, 2026. Used under fair use guidelines.

Food Group	Daily Serving for 2-year-old	Examples
Grains	About 3 ounce-equivalents of grains, ideally whole grains	3 slices of bread 1 slice of bread, plus 1 ounce of cereal, and ½ cup of cooked whole-grain rice or pasta
Proteins	2 ounce-equivalents of meat, poultry, fish, eggs, or legumes	1 ounce of lean meat or chicken, plus one egg 1 ounce of fish, plus ¼ cup of cooked beans
Fruits	1 cup-equivalent of fresh, frozen, canned, and/or dried fruits, or 100 percent fruit juice	1 small apple cut into slices 1 cup of sliced or cubed fruit ½ cup dried fruit
Vegetables	1 cup-equivalent of raw and/or cooked vegetables	1 cup of pureed, mashed, or finely chopped cooked or raw vegetables (such as sweet potato, chopped broccoli, or tomato sauce) 2 cups raw or 1 cup cooked leafy greens
Dairy Products	2 cup-equivalents per day	2 cups of dairy milk 1 cup of dairy milk, plus 1.5 ounces of natural cheese 1 cup of dairy milk, plus 1 cup of dairy yogurt

Macronutrients

For carbohydrate intake, the Acceptable Macronutrient Distribution Range (AMDR) is 45 to 65 percent of daily calories for toddlers (113 to 163 grams for 1,000 daily calories). The AMDR for protein for toddlers is 5 to 20 percent of daily calories (13 to 50 grams for 1,000 daily calories). The AMDR for fat for toddlers is 30 to 40 percent of daily calories (33 to 44 grams for 1,000 daily calories). Essential fatty acids are vital for the development of the eyes, nerves, and other tissues. Toddlers, like everyone else, should not consume foods with high amounts of trans fats. Children under 2 years have more room in their diet for saturated fats than those 2 years and older. A healthy dietary pattern for young children may include the equivalent of 3-4 teaspoons of healthy oils, such as canola oil, each day.

Micronutrients

Growing needs for vitamins and minerals can be met with a balanced diet, with a few exceptions. Toddlers and children of all ages need 15 micrograms (600 IU) of vitamin D per day. Vitamin D-fortified milk and cereals can help to meet this need. However, toddlers who do not get enough of this micronutrient should receive a supplement. Pediatricians may also prescribe a fluoride supplement for toddlers who live in areas with fluoride-poor water. Iron deficiency is relatively common in children.^[2].

Learning How to Handle Food

As children grow older, they enjoy taking care of themselves, which includes self-feeding. During this phase, it is important to offer children foods that they can handle on their own and that help them avoid choking. Examples include fresh fruits sliced into pieces, orange or grapefruit sections, peas or potatoes mashed for safety, yogurt, and whole-grain bread or bagels cut into pieces. Parents can help children learn to feed themselves by providing:

• small utensils that fit a young child’s hand
• small cups that will not tip over easily
• plates with edges to prevent food from falling off
• small servings on a plate
• high chairs, booster seats, or cushions to reach a table

Parents and other caregivers may be challenged by a toddler’s pickiness or messiness. Experts suggest that healthy foods be offered in a calm and consistent environment, with adults and older children present to model healthy meal habits. Repeated offerings of new foods might be necessary before a child embraces them. Toddlers may have periods of low or high appetite. A child’s growth rate slows after infancy; if a toddler is growing normally and playing energetically, a short period of low intake should not be cause for concern.

Toddler Obesity

The CDC estimates that about 20% of US children aged 2-19 years, about 14.7 million children, have obesity.^[3] Among people receiving income-based nutrition assistance and education in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), children aged 2-4 years had an obesity prevalence of 14.4% and an overweight prevalence of 15.4%.^[4] Obesity during early childhood tends to linger as a child matures and causes health problems later in life.

Iron-Deficiency Anemia

A toddler who does not eat enough iron-rich foods can develop iron-deficiency anemia. Iron is a component of hemoglobin, which transports oxygen throughout the body. Iron-deficiency anemia causes weakness, pale skin, shortness of breath, and irritability and can lead to intellectual, behavioral, or motor problems. Iron-deficiency anemia can occur as young children are weaned from iron-rich foods, such as breast milk and iron-fortified formula.

Iron-rich foods for a toddler include lean meats, fish, poultry, eggs, legumes, and iron-enriched whole-grain breads and cereals. A toddler’s diet should provide 7 to 10 milligrams of iron daily. Although milk is critical for the bone-building calcium that it provides, intake should not exceed the RDA to avoid displacing foods rich with iron. Children may also be given a daily supplement. If iron-deficiency anemia does occur, treatment includes a dosage of 3 milligrams per kilogram once daily before breakfast, usually in the form of a ferrous sulfate syrup. Consuming vitamin C, such as orange juice, can improve iron absorption.^[5]

References

1. Polan EU, Taylor DR. Journey Across the LifeSpan: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 108.
2. American Academy of Pediatrics. “Serving Sizes for Toddlers – HealthyChildren.org.” https://www.healthychildren.org/English/ages-stages/toddler/nutrition/Pages/Serving-Sizes-for-Toddlers.aspx Updated January 1, 2024. Accessed May 24, 2026.
3. American Academy of Pediatrics. “Nutrition – HealthyChildren.org.” https://www.healthychildren.org/English/ages-stages/baby/feeding-nutrition/Pages/default.aspx Accessed October 20, 2025.
4. U.S. Centers for Disease Control and Prevention. “Childhood Obesity Facts.” https://www.cdc.gov/obesity/childhood-obesity-facts/childhood-obesity-facts.html Updated April 2, 2024. Accessed October 20, 2025.
5. U.S. Centers for Disease Control and Prevention. “Fast Facts: Obesity Among Children in WIC.” https://www.cdc.gov/obesity/data-and-statistics/facts-about-obesity-among-young-children-enrolled-in-wic.html. Updated April 18, 2024. Accessed October 20, 2025.
6. Louis A, Kazal JR. Prevention of Iron Deficiency in Infants and Toddlers. American Academy of Family Physicians. 2002;  66(7), 1217-25. https://www.aafp.org/pubs/afp/issues/2002/1001/p1217.html. Accessed October 20, 2025.

Childhood (4-8 years)

From ages four to eight, children grow at a slower rate than infants and toddlers. They also experience the loss of deciduous, or “baby,” teeth and the arrival of permanent teeth. As new teeth come in, many children have some malocclusion, or malposition, of their teeth, which can affect their ability to chew food. Other changes that affect nutrition include the influence of peers and the kinds of foods offered by schools and afterschool programs, which can make up a sizable part of a child’s diet. Food-related problems for young children can include tooth decay, food sensitivities, and malnourishment. Excessive weight gain early in life can lead to obesity into adolescence and adulthood.

A healthy diet facilitates healthy growth and development. Children grow 2–3 inches (5–7 centimeters) in height and 4.5–6.5 pounds (2–3 kilograms) in weight per year. Extremities grow faster than the trunk, which results in more adult-like proportions. Long-bone growth stretches muscles and ligaments, which can result in localized “growing pains.”^[1]

Energy

Children’s energy requirements depend on age, activity level, and sex. Females age four to eight require 1,200 to 1,800 calories a day, while males require 1,200 to 2,000 calories daily. Recommended intakes of macronutrients and most micronutrients are higher relative to body size than nutrient needs of adults. Therefore, children should be provided nutrient-dense food at meal- and snack-time. It is important not to overfeed children, especially with nutrient-poor snacks, as this can lead to childhood obesity. Parents and other caregivers can turn to sources such as the American Academy of Pediatrics for guidance.

Macronutrients

For carbohydrates, the Acceptable Macronutrient Distribution Range (AMDR) is 45–65 percent of daily calories (which is equivalent to 135–195 grams for 1,200 daily calories). Foods rich in complex carbohydrates – fruits, vegetables, whole grains, and legumes – should make up the bulk of these. Children should eat 17–25 grams of fiber per day. The AMDR for protein is 10–30 percent of daily calories (30–90 grams for 1,200 daily calories). Children have a high need for protein to support muscle growth and development. High levels of essential fatty acids are needed to support growth, although not as high as in infancy and the toddler years. As a result, the AMDR for fat is 25–35 percent of daily calories (33–47 grams for 1,200 daily calories).

Micronutrients

Micronutrient needs should be met with foods first. Parents and caregivers should select a variety of foods from each food group to provide micronutrients. Because children grow rapidly, they require foods that are high in iron, such as lean meats, legumes, fish, poultry, and iron-enriched cereals. Adequate fluoride is crucial to support strong teeth. Crucial micronutrients include calcium and vitamin D to build dense bones and a strong skeleton. Children who do not consume adequate vitamin D should be given a supplement.

Table 18.6 RDAs (and AIs) for Micronutrients During Childhookd, 4-8 years. Source: Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press. 2011. Used under fair use guidelines.

Nutrient	RDA (or AI*) Children, Ages 4–8
Vitamin A (µg RAE)	400
Thiamin (B1) (µg)	600
Riboflavin (B2) (µg)	600
Niacin (B3) (mg)	8.0
Vitamin B6 (µg)	600
Folate (µg)	200
Vitamin B12 (µg)	1.2
Vitamin C (mg)	25
Vitamin D (µg)	15
Vitamin E (mg)	7.0
Vitamin K (µg)	55*
Calcium (mg)	1000
Iron (mg)	10
Magnesium (mg)	130
Phosphorus (mg)	500
Selenium (mcg)	30
Zinc (mg)	5.0

Factors Influencing Intake

Many factors influence children’s eating habits and attitudes toward food. Family environment, societal trends, taste preferences, and messages in the media all impact children’s food attitudes and preferences. Television commercials can entice children to consume sugary products, fatty fast-foods, excess calories, refined ingredients, and sodium. Therefore, it is critical that parents and caregivers direct children toward healthy choices.

One way to encourage children to eat healthy foods is to make meal- and snack-time fun and interesting. Parents should include children in food planning and preparation, for example selecting items while grocery shopping or helping to prepare part of a meal, such as making a salad. It might be helpful to cut sandwiches, meats, or pancakes into small or interesting shapes. Parents should offer nutritious desserts, such as fresh fruits, instead of calorie-laden cookies, cakes, salty snacks, and ice cream. Studies show that children who eat family meals on a frequent basis consume more nutritious foods.[2]

Children and Malnutrition

Malnutrition is a problem for many children, in both developing nations and the developed world. Even with the wealth of food in North America, many children grow up malnourished or even hungry. The USDA characterizes households into the following groups:

• high food security;
• marginal food security;
• low food security;
• very low food security.

Millions of children grow up in food-insecure households with inadequate diets due to both the amount of available food and the quality of food. In the United States in 2023, about 18 percent of households with children experienced food insecurity to some degree. In half of those, only adults experienced food insecurity, while in the other half both adults and children are food insecure, which means that both adults and children did not have access to adequate, nutritious meals at times.[3]

Deficiencies in iron, zinc, protein, and vitamin A can result in stunted growth, illness, and limited development. Federal programs, such as the National School Lunch Program, the School Breakfast Program, and Summer Feeding Programs, work to address the risk of hunger and malnutrition in school-aged children. They help to fill the gaps and provide children living in food-insecure households with greater access to nutritious meals.

The National School Lunch Program

Beginning with preschool, most children consume at least one meal daily in a school setting. Many children receive both breakfast and lunch outside of the home. Therefore, it is important for schools to provide meals that are nutritionally sound. In the United States, approximately thirty million children from low-income families were served meals provided by the National School Lunch Program per year in the late 2010s.^[4] This federally-funded program offers low-cost or free lunches to schools. School districts that take part receive subsidies from the US Department of Agriculture (USDA) for every meal they serve. School lunches must meet the USDA Dietary Guidelines for Americans to receive federal subsidies.

Food Allergies and Food Intolerance

Development of food allergies is an issue for school-aged children. In 2021, 5.8% of children under age eighteen were reported to be allergic to at least one type of food.^[5] The most common allergenic foods include peanuts, milk, eggs, soy, wheat, and shellfish. An allergy occurs when a protein in food triggers an immune response, which results in the release of antibodies, histamine, and other defenders that attack foreign bodies. Possible symptoms include itchy skin, hives, abdominal pain, vomiting, diarrhea, and nausea; in the most serious cases, constriction of the trachea and anaphylaxis can occur. Symptoms usually develop minutes to hours after consuming a food allergen. Children can outgrow a food allergy, especially allergies to wheat, milk, eggs, or soy.

Anaphylaxis is a life-threatening reaction that results in difficulty breathing, swelling in the mouth and throat, decreased blood pressure, shock, or even death. Milk, eggs, wheat, soybeans, fish, shellfish, peanuts, and tree nuts are the most likely to trigger this type of response.

References

1. Polan EU, Taylor DR. Journey Across the LifeSpan: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 150–51.
2. Hammons AH, Fiese BH. “Is Frequency of Shared Family Meals Related to the Nutritional Health of Children and Adolescents?” Pediatrics. 2011; 127(6): e1565-e1574. https://doi.org/10.1542/peds.2010-1440
3. Rabbitt MP, Reed-Jones M, Hales LJ, Burke MP. Household food security in the United States in 2023 (Report No. ERR-337). US Department of Agriculture, Economic Research Services. 2024. https://search.nal.usda.gov/discovery/fulldisplay?context=L&vid=01NAL_INST:MAIN&docid=alma9916546833607426
4. National School Lunch Program Fact Sheet. US Department of Agriculture, Food and Nutrition Service. Published March 4, 2021. https://www.fns.usda.gov/fns-101-nslp
5. Zablotsky B, Black LI, Akinbami LJ. “Diagnosed allergic conditions in children aged 0-17 years: United States, 2021.” NCHS Data Briefs, number 459, January 2023. Hyattsville, MD: National Center for Health Statistics. 2023. https://dx.doi.org/10.15620/cdc:123250

Early Adolescence (9-13 years)

In DRI tables, adolescence is divided into early (ages 9 – 13) and late phases (ages 14 – 18). Important physiological changes that take place include the development of primary sex characteristics, the onset of menstruation in females, and the appearance of secondary sex characteristics. Facial and body hair grow, breasts develop in females and the voice may deepen in males. Other physical changes include rapid growth and alterations in body proportions. All these changes, as well as the accompanying mental and emotional adjustments, should be supported with sound nutrition.

Physical development includes an increase in height by 20 to 25 percent. Puberty is second to the prenatal period in terms of rapid growth as the long bones reach their final, adult size. Females grow 2–8 inches (5–20 centimeters) taller, while males grow 4–12 inches (10–30 centimeters) taller. Weight gain is associated with the development of bone, muscle, and fat tissue.

Energy and Macronutrients

The energy requirements for preteens depend on gender, activity level, and current growth rate. For ages nine to thirteen, healthy females need about 1,400 to 2,200 kcals and males from 1,600 to 2,600 kcals per day.

For carbohydrates, the AMDR is 45 to 65 percent of daily kcals (which is a recommended daily allowance of 158–228 grams for 1,400–1,600 daily kcals). Carbohydrate-rich foods high in fiber should make up the bulk of intake. The AMDR for protein is 10 to 30 percent of daily kcals (35–105 grams for 1,400 daily kcals and 40–120 grams for 1,600 daily kcals). The AMDR for fat is 25 to 35 percent of daily kcals (39–54 grams for 1,400 daily kcals and 44–62 grams for 1,600 daily kcals).

Micronutrients

Key vitamins needed during puberty include D, K, and B12. Adequate calcium intake is essential for building bone and preventing osteoporosis later in life. Young females need more iron at the onset of menstruation, while young males need additional iron for the development of lean body mass. Almost all these needs should be met with dietary choices, not supplements (iron is an exception).

Table 18.7 RDAs (and AIs) During Preteenhood, 9-13 Years. Source: National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Washington, DC: The National Academies Press. 2019. Used under fair use guidelines.

Nutrient	RDA (or AI*) Preteens, Ages 9–13
Vitamin A (µg/day)	600
Thiamine (B1) (µg/day)	900
Riboflavin (B2) (µg/day)	900
Niacin (B3) (mg/day)	12
Vitamin B6 (mg/day)	1.0
Folate (µg/day)	300
Vitamin B12 (µg/day)	1.8
Vitamin C (mg/day)	45
Vitamin D (µg/day)	15
Vitamin E (mg/day)	11
Vitamin K (µg/day)	60*
Calcium (mg/day)	1,300
Iron (mg/day)	8
Magnesium (mg/day)	240
Phosphorus (mg/day)	1,250
Potassium (mg/day)	2,500* (male), 2,300* (female)
Selenium (µg/day)	40
Zinc (mg/day)	8

Late Adolescence (14-18 years)

After puberty, the rate of physical growth slows down. An important psychological and emotional change is the desire for independence as adolescents develop identities apart from their families. [1] They have their own money to purchase food and tend to eat more meals away from home. Older adolescents also can be curious and open to new ideas, which includes trying new kinds of food and experimenting with their diet. Poor choices can make young people nutritionally vulnerable.

As teenagers make more dietary decisions, caring adults should guide them toward appropriate, nutritious choices. Teens should be discouraged from eating fast food, which has a high fat and sugar content, or frequenting convenience stores and using vending machines, which typically offer poor nutritional selections. Other challenges that teens may face include obesity and eating disorders. At this life stage, young people still need guidance from caring adults. Healthy eating habits can support activities they enjoy, such as skateboarding or dancing, or connect to their desires or interests, such as a lean figure, athletic performance, or improved cognition.

During late adolescence, males and females grow and develop differently. Females experience the increase in body fat that eventually is necessary for healthy pregnancy and lactation. Males increase in muscle and bone mass. For both, growth slows with the end of puberty. Motor functions of an older adolescent are comparable to those of an adult.^[1] Again, adequate nutrition and healthy choices support this stage of growth and development.

Energy and Macronutrients

Nutrient needs are greater in adolescence than at any other time, except during pregnancy, and many adolescents have increased appetites. The energy requirements for older teens are 1,800 to 2,400 kcals and 2,000 to 3,200 kcals for females and males, respectively, depending on activity level. The extra energy required for physical development should be obtained from foods that provide nutrients instead of “empty calories.” Also, teens who participate in sports must eat enough to meet their increased energy needs.

Adolescents are more responsible for their dietary choices than children, but parents and caregivers should remain involved to make sure that teens meet their nutrient needs. For carbohydrates, the AMDR is 45 to 65 percent of daily kcals (203–293 grams for 1,800 daily kcals). Adolescents require more servings of grain than younger children, and should eat whole grains, such as wheat, oats, barley, and brown rice. The Institute of Medicine recommends higher intakes of protein for growth. The AMDR for protein is 10 to 30 percent of daily kcals (45–135 grams for 1,800 daily kcals), and lean proteins, such as meat, poultry, fish, beans, nuts, and seeds are excellent ways to meet those nutritional needs.

The AMDR for fat is 25 to 35 percent of daily kcals (50–70 grams for 1,800 daily kcals). The recommendation for fiber is 26-38 grams per day. It is essential for young athletes and other physically active teens to drink plenty of fluids to prevent dehydration.

Micronutrients

Micronutrient recommendations for adolescents are like those for adults. Higher nutrient recommendations include calcium and phosphorus for bone growth. Iron and zinc recommendations are higher for blood health and growth. As for all ages, vitamins and minerals are best obtained from varied, healthy foods first, with supplementation for certain micronutrients only (such as iron).

Important micronutrients for adolescents include calcium, vitamin D, vitamin A, and iron. Calcium and vitamin D are essential for building bone mass. The recommendation for calcium is 1,300 milligrams (mg) for both boys and girls. Low-fat milk and cheese are excellent sources of calcium and help young people avoid saturated fat and cholesterol. Products fortified with calcium, such as breakfast cereals and orange juice, can help meet this need. Iron supports the growth of muscle and lean body mass. Adolescent females require 15 mg of iron per day both for growth and to replace iron lost in menstruation. Vitamin C from orange juice and fresh fruits and vegetables aids iron absorption, particularly iron from plant sources. Generous fruit and vegetable intake also helps meet vitamin A needs.

Table 18.8 RDAs (and AIs) During Older Adolescence, 14-18 Years. Source: National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Washington, DC: The National Academies Press. 2019. Used under fair use guidelines.

Nutrient	RDA (or AI*) Males, Ages 14–18	RDA (or AI*) Females, Ages 14–18
Vitamin A (µg/day)	900	700
Thiamine (B1) (mg/day)	1.2	1.0
Riboflavin (B2) (mg/day)	1.3	1.0
Niacin (B3) (mg/day)	16	14
Vitamin B6 (mg/day)	1.3	1.2
Folate (µg/day)	400	400
Vitamin B12 (µg/day)	2.4	2.4
Vitamin C (mg/day)	75	65
Vitamin D (µg/day)	15	15
Vitamin E (mg/day)	15	15
Vitamin K (µg/day)	75*	75*
Calcium (mg/day)	1,300	1,300
Iron (mg/day)	11	15
Magnesium (mg/day)	410	360
Phosphorus (mg/day)	1,250	1,250
Potassium (mg/day)	3,000*	2,300*
Selenium (µg/day)	55	55
Zinc (mg/day)	11	9

Eating Disorders

Many teens struggle with eating disorders. A study of adolescents 13-18 years old in the early 2000s found a lifetime prevalence of eating disorders of 2.7%.^[2] These disorders are more prevalent among adolescent girls but have increased among adolescent boys. Disordered eating can lead to malnourishment and a variety of health risks.

Eating disorders involve extreme behavior related to food and exercise, including both undereating and overeating. Some of these conditions include:

Anorexia Nervosa. Potentially fatal, characterized by under eating and excessive weight loss. People with this disorder are preoccupied with dieting, calories, and food intake to an unhealthy degree. Anorexics have a poor body image, which leads to anxiety, avoidance of food, a rigid exercise regimen, fasting, and a denial of hunger. The condition predominantly affects females. Between 0.5 and 1 percent of American women and girls suffer from this eating disorder.

Binge-Eating Disorder. People who suffer from binge-eating disorder experience regular episodes of eating an extremely large amount of food in a short period of time. Binge eating is a compulsive behavior, and people who suffer from it typically feel it is beyond their control. This behavior often causes feelings of shame and embarrassment, and leads to obesity, high blood pressure, high cholesterol levels, Type 2 diabetes, and other health problems. Both males and females suffer from binge-eating disorder. It affects 1 to 5 percent of the population.

Bulimia Nervosa. Bulimia nervosa is characterized by alternating cycles of overeating and undereating. People who suffer from it may binge followed by compensatory behavior, such as self-induced vomiting, laxative use, and compulsive exercise. As with anorexia, most people with this condition are female. Approximately 1 to 2 percent of American women and girls have this eating disorder.^[3]

Eating disorders are associated with stress, low self-esteem, and other psychological and emotional issues. It is important for parents to watch for signs and symptoms of these disorders, including sudden weight loss, lethargy, vomiting after meals, and the use of appetite suppressants. Eating disorders can lead to serious complications including death if untreated. Treatment includes cognitive, behavioral, and nutritional therapy.

Childhood and Adolescent Obesity

Children need adequate caloric intake for growth, and it is important not to impose very restrictive diets. However, exceeding caloric requirements on a regular basis can lead to childhood obesity. Approximately one of five US children and adolescents are obese.^[4]

Some factors associated with this include:

• larger portion sizes
• limited access to nutrient-rich foods
• increased access to fast foods and vending machines
• lack of breastfeeding support
• declining physical education programs in schools
• insufficient physical activity and a sedentary lifestyle
• media messages encouraging the consumption of unhealthy foods

Children who suffer from obesity are more likely to become overweight or obese adults. Obesity affects self-esteem, energy, and activity level and is a major risk factor for diseases later in life, including cardiovascular disease, Type 2 diabetes, stroke, hypertension, and certain cancers.^[5]

Programs to address childhood obesity can include behavior modification, exercise counseling, psychological support or therapy, family counseling, and family meal-planning advice. For most, the goal is not weight loss, but rather allowing height to catch up with weight as the child continues to grow. Rapid weight loss is not recommended for preteens or younger children.

References

1. Polan EU, Taylor DR. Journey Across the LifeSpan: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 171–76.
2. Eating Disorders. National Institute of Mental Health. https://www.nimh.nih.gov/health/statistics/eating-disorders. N.D. Accessed March 4, 2026.
3. Types of Eating Disorders: Symptoms and Treatments. National Eating Disorders Association. https://www.nationaleatingdisorders.org/what-are-eating-disorders/. Accessed February 13, 2026.
4. Childhood Obesity Facts. Centers for Disease Control and Prevention. https://www.cdc.gov/obesity/childhood-obesity-facts/childhood-obesity-facts.html. Updated April 2, 2024. Accessed March 3, 2026.
5. Obesity and Overweight Fact Sheet. World Health Organization. https://www.who.int/en/news-room/fact-sheets/detail/obesity-and-overweight. Updated December 2025. Accessed February 13, 2026.

Young Adulthood (19-30 years)

During young adulthood, the body is more stable than during childhood and adolescence. Physical growth has been completed and body systems are fully developed. Typically, a young adult who is active has reached his or her physical peak. For example, vital capacity, or the maximum amount of air that the lungs can inhale and exhale, is at its peak between the ages of twenty and forty.^[1] It important to continue to practice good nutrition for metabolic function, repair and regeneration, prevention of chronic conditions, enjoying a healthy lifestyle, and even thinking about becoming a parent.

Energy and Macronutrients

Energy needs of males tend to be higher than that of females during this period, with averages of 1,800 to 2,400 calories for females, and 2,400 to 3,000 calories for males. These estimates do not include those who are pregnant or breastfeeding, who require a higher energy intake. For carbohydrates, the AMDR is 45 to 65 percent of daily calories. All adults should eat fewer energy-dense carbohydrates, especially refined, sugar-dense sources and seek nutrient rich whole fruits, vegetables, and whole grains. The AI for fiber is 25 grams per day for females and 38 grams per day for males. Soluble fiber may help improve cholesterol and blood sugar levels, while insoluble fiber can help prevent constipation.

The AMDR for protein is 10 to 35 percent of total daily calories and should include a variety of lean meat and poultry, eggs, beans, peas, nuts, and seeds. Protein-rich foods containing unsaturated fats, such as legumes, fish, and low-fat meats, are preferable to meats high in saturated fat. Adults should limit total fat to 20 to 35 percent of their daily calories and keep saturated fats to less than 10 percent of total kcals. Trans fats are particularly dangerous, and adding trans fats to foods in the U.S. is no longer legal. Small amounts of trans fats occur naturally in beef, mutton, and dairy products. These types and amounts are less worrisome from a health standpoint.

Micronutrients

Micronutrient needs in adults differ slightly according to sex. Intense activity and perspiration can increase the need for sodium, potassium, and magnesium. Males require more of vitamins C and K, along with thiamine, riboflavin, and niacin. Females require extra iron due to menstruation. Therefore, it can be beneficial for some young adults to follow a daily multivitamin regimen to help meet nutrient needs. But as always, “food first, supplements second.”

Table 18.9 RDAs (and AIs) During Young Adulthood, 19-30 Years. Source: National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Washington, DC: The National Academies Press. 2019. Used under fair use guidelines.

Nutrient	RDA (or AI*) Adult Males	RDA (or AI*)Adult Females
Vitamin A (µg/day)	900	700
Thiamin (mg/day)	1.2	1.1
Riboflavin (mg/day)	1.3	1.1
Niacin (mg/day)	16	14
Vitamin B6 (mg/day)	1.3	1.3
Folate (µg/day)	400	400
Vitamin B12 (µg/day)	2.4	2.4
Vitamin C (mg/day)	90	75
Vitamin D (µg/day)	15	15
Vitamin E (mg/day)	15	15
Vitamin K (µg/day)	120*	90*
Calcium (mg/day)	1,000	1,000
Iron (mg/day)	8	18
Magnesium (mg/day)	400	310
Phosphorus (mg/day)	700	700
Potassium (mg/day)	3,400*	2,600*
Selenium (µg/day)	55	55
Zinc (mg/day)	11	8

Nutritional Concerns in Young Adulthood

The adequate intake (AI) of water for males is 3.7 liters per day, and for females 2.7 liters, from food and liquids.^[2] It is best to drink plenty of plain water and avoid sugary beverages such as soda, coffee drinks, and energy drinks. Fresh fruits and vegetables, including watermelon and cucumbers, are excellent food sources of fluid. In addition, young adults should avoid consuming excessive amounts of sodium, which can lead to high blood pressure and its complications. It is best to limit sodium to less than 2,300 milligrams per day.

Obesity during Adulthood

For adults, BMI above 25 is considered overweight, and BMI over 30 is obese. By that measurement, obesity prevalence among US adults was about 40% when measured in 2021-2023.^[3] As during childhood and adolescence, physical inactivity and poor dietary choices are major contributors to obesity in adulthood. Solid fats, alcohol, and added sugars (SoFAAS) make up 35 percent of total calories for most people; these foods tend to be high in saturated fat and low in fiber and micronutrients. Limiting highly processed foods can lower the risk of weight gain and nutrient deficiencies.

References

1. Polan EU, Taylor DR. Journey Across the Life Span: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 192–93.
2. Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. 2005. Washington, DC: The National Academies Press. https://doi.org/10.17226/10925. Accessed December 10, 2017.
3. Emmerich SD, Fryar CD, Stieman B, Ogden CL. Obesity and Severe Obesity Prevalence in Adults: United States, August 2021-August 2023. NCHS Data Brief, no. 508. Hyattsville, MD: National Center for Health Statistics, 2024. https://dx.doi.org/10.15620/cdc/159281

Middle Adulthood (31-50 years)

Important priorities during these years include becoming parents, raising children, focusing on career, maintaining homes, and even caring for older relatives. While many people are so busy that health and exercise aren’t the first priorities, healthy habits can help in life enjoyment and increase the chances of healthy older age. For women, this stage can include pregnancies and lactation and the transition into perimenopause, the period before menopause and the end of menstruation and fertility.

Other physical changes include loss of bone mass and visual acuity, and by age forty there can be a decreased ability to see objects at a close distance, a condition known as presbyopia.^[1] Wrinkles begin to appear, and joints ache after a highly active day. Muscle tone and elasticity in the connective tissue may decline.^[2] Many people a decline in endurance, the onset of osteoarthritis, and changes in the digestive system. Wounds and other injuries may take longer to heal. Body composition changes due to fat deposits in the trunk. To maintain health and wellness during the middle-aged years and beyond, it is important to:

• maintain a healthy body weight
• consume nutrient-dense foods
• drink alcohol moderately or not at all
• be a nonsmoker
• engage in moderate physical activity at least 150 minutes per week

Energy and Macronutrients

The daily energy requirements for ages thirty-one to fifty are 1,800 to 2,200 kcals for females and 2,200 to 3,000 kcals for males, depending on activity level. These estimates do not include women who are pregnant or breastfeeding. Typical western dietary patterns do not match the recommended guidelines. A 2005 study found that five foods—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—accounted for over half of all vegetable intake at the time; the low cost of these foods may help explain their popularity, as more nutrient-dense foods tend to be more expensive.^[3] Following the dietary guidelines in the middle-aged years provides adequate but not excessive energy, macronutrients, vitamins, and minerals.

The AMDRs for carbohydrates, protein, fat, fiber, and fluids remain the same from young adulthood into middle age. It is important to avoid putting on excess pounds and limiting an intake of SoFAAS to help avoid cardiovascular disease, diabetes, and other chronic conditions.

Micronutrients

There are some differences, however, regarding micronutrients. For males, the recommendation for magnesium increases to 420 milligrams daily, while middle-aged females should increase their intake of magnesium to 320 milligrams per day. Other key micronutrients needed during the middle-aged years include folate and vitamins B6 and B12 to prevent elevation of homocysteine, a byproduct of metabolism that can damage arterial walls and lead to atherosclerosis, a cardiovascular condition. People who may become pregnant are recommended to supplement folate to protect against fetal neural tube defects in the case of pregnancy. (Aside from magnesium, the actual DRIs do not change so much as bear careful watching.) Foods rich in these nutrients include fruits, vegetables, and lean meats.

Menopause

At an average age of 50, production of estrogen and progesterone by the ovaries falls, leading to the end of menstruation in females. Menopausal changes may include hot flashes, night sweats, and mood changes, and alterations in body composition, such as weight gain in the abdominal area. Bone loss is related to menopause due to the hormone changes. Bone loss increases the risk of fractures, which can affect mobility and the ability to complete everyday tasks.^[4]

Recommendations for those experiencing menopause or perimenopause (the stage just prior to the end of the menstruation) include:

• consuming a variety of whole grains, and other nutrient-dense foods
• maintaining a diet high in fiber, low in fat, and low in sodium
• avoiding caffeine, spicy foods, and alcohol
• eating foods rich in calcium, or taking physician-prescribed calcium supplements and vitamin D
• doing stretching exercises to improve balance and flexibility and reduce the risk of falls and fractures.

References

1. Polan EU, Taylor DR. Journey Across the Life Span: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 192–93.
2. Polan EU, Taylor DR. Journey Across the Life Span: Human Development and Health Promotion. Philadelphia: F. A. Davis Company; 2003, 212–213.
3. Drewnowski A, Darmon, N. Food Choices and Diet Cost: An Economic Analysis. The Journal of Nutrition. 2005; 135(4), 900-904. https://doi.org/10.1093/jn/135.4.900.
4. Escobar SN. Nutrition and Menopause. Academy of Nutrition and Dietetics. https://www.eatright.org/health/wellness/healthful-habits/nutrition-and-menopause Published May 12, 2025. Accessed February 13, 2026.

Older Adulthood (51+ years)

Physiological and emotional changes during this life stage include serious health challenges, such as cancer, heart disease, diabetes, or dementia. Both sexes experience a loss of hormone production, muscle mass, and strength. Fat deposits build up in the abdominal area, which increases the risk for Type 2 diabetes and cardiovascular disease. The skin becomes thinner and may take longer to heal after an injury. The heart may become less efficient, and kidneys may become less effective in excreting metabolic products such as sodium, acid, and potassium. This can alter water balance and increase the risk for over- or underhydration. In addition, immune function may decrease, and there the absorption of vitamins and minerals in the intestines may decline. Short-term memory might not be as keen as it once was.^[1]

Disorders of the nervous system can have profound effects. Elderly adults who suffer from dementia may experience memory loss, agitation, and delusions. One in eight people over age sixty-four and almost half of all people over eighty-five suffer from Alzheimer’s disease, which is the most common form of dementia.^[2] Neurological disorder and psychological conditions, such as depression, can influence attitudes toward food as well as the ability to prepare or ingest food. Dental problems can lead to difficulties with chewing and swallowing, which in turn can make it hard to maintain a healthy diet. There also is a decreased thirst response in the elderly, and the kidneys have a decreased ability to concentrate urine, which can lead to dehydration.

Some adults gain weight due to decreased activity level and overeating due to stress or boredom. Others lose weight or develop nutrient deficiencies due to changes in social situations, lack of mobility, lack of access to healthy food, loss of enjoyment from food due to physical or emotional changes. Avoiding either being overweight or underweight is important. In addition, absorption of some nutrients in the small intestine declines with age; adjusting intake and supplementation is important to meet nutritional needs.

However, many older adults continue to be active, with nutrition being an important factor for good health. Older adults should continue to consume nutrient-dense foods and remain physically active.

Energy and Macronutrients

Due to reductions in lean body mass and metabolic rate, older adults require less energy than younger adults. Daily energy requirements are 1,600 to 2,200 kilocalories for females and 2,000 to 2,800 kilocalories for males, depending on activity level. The AMDRs for carbohydrates, protein, and fat remain the same from middle age into old age. Older adults should continue to eat whole grains or brown rice rather than refined starches. Fiber is important in preventing constipation and diverticulitis and may reduce the risk of colon cancer. Fiber AIs decrease as caloric requirements get lower, 30 grams for males and 21 grams for females. Lean proteins and healthy fats, including omega-3 fatty acids, are recommended for this age group as well.

Micronutrients

Vitamin B₆ RDAs rise to 1.7 and 1.5 mg per day for older males and females, respectively, to help lower homocysteine and protect against cardiovascular disease. Recommendations for calcium and vitamins D and B6 increase in old age, and awareness of poor B12 absorption is important. For adults over 70, the calcium RDA increases to 1,200 mg and the vitamin D increases to 20 µg to slow bone loss. As adults age, the production of stomach acid can decrease and lead to an overgrowth of bacteria in the small intestine. This can affect the absorption of vitamin B₁₂, so older adults may need to intake more B₁₂ to compensate. Vitamin B12 is needed for healthy brain function. Iron requirements are lower for older females due to the cessation of menstruation; males and females in this age group have similar iron needs. As is the case with all age groups, older adults should eat minimally-processed foods rich in micronutrients.

Sensory Issues

As we age, our taste receptors decrease in size and number. As a result, the taste threshold is higher in older adults, meaning that more of the same tasty molecules must be present to be detected. This can make food less appealing and decrease a person’s interest in eating. An intake of foods high in sugar and sodium can increase due to an inability to discern those tastes. The sense of smell also decreases which impacts attitudes toward food. Sensory issues may also affect the digestion because the taste and smell of food stimulates the secretion of digestive enzymes in the mouth, stomach, and pancreas.

Obesity in Old Age

Being overweight or obese increases the risk for cardiovascular disease (the leading cause of death in the United States) and diabetes (which causes about ninety-five thousand deaths in the United States annually).^[3] Obesity is also a contributing factor for other conditions, including arthritis.

For older adults who are overweight or obese, dietary changes to promote weight loss should be combined with an exercise program to protect muscle mass. Dieting can reduce muscle as well as fat, which can exacerbate the loss of muscle mass due to aging. Although weight loss among the elderly can be beneficial, it is best to consult a healthcare professional before beginning a weight-loss program.

The Anorexia of Aging

Anorexia of aging is characterized by poor food intake, which results in dangerous weight loss. Risks of being underweight include a higher risk for immune deficiency, falls, muscle loss, and cognitive deficits. Reduced muscle mass and physical activity mean that older adults need fewer calories per day. It is important for health care providers to examine the causes for anorexia of aging among their patients. Decreased intake may be due to disability, lack of mobility, access to food, poverty, loneliness, inability to cook, loss of taste, depression, or other factors.

Nutritional interventions should focus primarily on a healthy diet. Remedies can include increasing the frequency of meals and adding healthy, high-calorie foods (such as nuts, potatoes, whole-grain pasta, and avocados) to the diet. Liquid supplements between meals may help to improve caloric intake.^[4] Health care professionals should consider a patient’s habits and preferences when developing a nutritional treatment plan.

Longevity and Nutrition

Nutrition in youth can impact health in older age, but it is never too late to make healthy changes. Good nutrition and regular physical activity can help you live longer and healthier. The right foods provide numerous benefits at every stage of life. They help an infant to grow, an adolescent to develop mentally and physically, a young adult to achieve his or her physical peak, and an older adult to cope with aging. Nutritious foods form the foundation of a healthy life at every age.

References

1. Beverly McMillan, Illustrated Atlas of the Human Body (Sydney, Australia: Weldon Owen, 2008), 260.
2. American Medical Association. Complete Guide to Prevention and Wellness. Hoboken, NJ: John Wiley & Sons, Inc.; 2008, 421.
3. Deaths and Mortality. Centers for Disease Control, National Center for Health Statistics. https://www.cdc.gov/nchs/fastats/deaths.htm. Updated January 9, 2026. Accessed February 13, 2026.
4. Morley, JE. Anorexia of Aging: Physiologic and Pathologic. Am J Clin Nutr. 1997; 66, 760–73.https://doi.org/10.1093/ajcn/66.4.760.  

Attributions

Adapted by Pattie S. Green, Ph.D. and Jonathan E. Pottle, Ph.D. at Tacoma Community College from Human Nutrition by University of Hawai‘i at Mānoa Food Science and Human which is licensed under a Creative Commons Attribution 4.0 International License. Specifically, the following parts are adapted here:

• Pregnancy
• Infancy
• Toddler Years
• Childhood
• Adolescence
• Late Adolescence
• Young Adulthood
• Middle Age
• Older Adulthood: the Golden Years