Chapter 7: Weight Management

Pattie Green; Jonathan Pottle

Chapter 7: Weight Management

Learning Objectives

By the end of this chapter, you will be able to:

Describe energy balance.
Estimate the energy requirement for a person.
Explain the three categories of energy expenditure.

Balancing Energy Input with Energy Output

To maintain weight, energy intake must balance energy output. Recall that the macronutrients you consume are either converted to energy, stored, or used to synthesize molecules that your body needs. A nutrient’s metabolic path is partly dependent upon energy balance. When you are in a positive energy balance, meaning that you are taking in more energy than you are expending, the excess nutrients will be stored or used to grow (e.g., during childhood, pregnancy, and wound healing). When you are in negative energy balance and aren’t taking in enough energy to meet your needs, and the body will used stored molecules to provide energy. Energy balance is achieved when intake of energy is equal to energy expended. Weight can be thought of as a whole body estimate of energy balance; body weight is maintained when the body is in energy balance. Weight is lost when the body is in negative energy balance and gained when it is in positive energy balance. However, many factors are involved in energy intake and energy expenditure. Some of these factors are under your control and others are not. We will discuss how to estimate a person’s energy needs and energy output. We will also consider the other factors with a role in maintaining energy balance and hence, body weight.

Estimating Energy Requirement

To maintain body weight, you must balance the calories obtained from food and beverages with the calories expended. We can estimate energy needs in kilocalories (kcal) per day using formulas developed by the Institute of Medicine. The Estimated Energy Requirement (EER) is a standardized mathematical prediction of a person’s daily energy needs, considering age, sex, weight, height, and physical activity level (PA; see Table 7.1). The constants within the formulas were derived from measurements of actual people. These formulas are appropriate for people over 18 who are at a healthy weight and not trying to gain or lose weight. They are not appropriate for children, pregnant or lactating women, or overweight or obese people.

$Adult\ male\ EER=662-\left[9.53\times a g e(y)\right]+PA\times\left[15.91\times w t(kg)+539.6\times h t(m)\right]$

$Adult\ female\ EER=354-\left[6.91\times a g e(y)\right]+PA\times\left[9.36\times w t(kg)+726\times h t(m)\right]$

Note: to convert pounds to kilograms, divide weight in pounds by 2.2. To convert feet to meters, divide height in feet by 3.3. A sample EER calculation is shown below.

Table 7.1 Physical Activity (PA) Categories and Values. These values apply only to normal weight adults and not to children, or pregnant or lactating women. Source: Institute of Medicine. 2006. *Dietary Reference Intakes: The Essential Guide to Nutrient Requirements.* Washington, DC: The National Academies Press. p.84. Used under fair use guidelines.
Activity Level	Men PA Value	Women PA Value	Description
Sedentary	1.00	1.00	No physical activity beyond that required for independent living
Low	1.11	1.12	Equivalent to walking 1.5 to 3 miles per day
Moderate	1.25	1.27	Equivalent to walking 3 to 10 miles per day
High	1.48	1.45	Equivalent to walking 10 or more miles per day

Sample EER Calculation

Here is a step-by-step calculation of EER for a hypothetical female person, age 49, moderately active, weighing 77 kg (170 lb.), 180 cm (5’11”) tall:

$EER=354-\left[6.91\times a g e\left(yr\right)\right]+PA\times\left[9.36\times w e i g h t\left(kg\right)+726\times h e i g h t\left(m\right)\right]$

$EER=354-\left[6.91\times49yr\right]+1.27\times\left[9.36\times77kg+726\times1.8m\right]$

$EER=354-338.59+1.27\times\left[720.7+1306.8\right]$

$EER=354-338.59+1.27\times\left[2027.5\right]$

$EER=354-338.59+2574.9$

$EER=2590\frac{kcal}{day}$

Table 7.2 shows the estimated daily kcal needs for different age groups of males and females with various activity levels included in the 2015 Dietary Guidelines for Americans. The Dietary Guidelines also state that it is important to obtain kcals from nutrient-dense foods and consume the various macronutrients in their Acceptable Macronutrient Distribution Ranges (AMDRs) (Table 7.3).

Table 7.2 Estimated Daily Calorie Needs. Source: 2010 Dietary Guidelines for Americans. US Department of Agriculture. Public Domain.
Sex	Age (years)	Sedentary	Moderately Active	Active
Child (female and male)	2–3	1,000	1,000–1,400 (male) 1,000-1,200 (female)	1,000–1,400
Female	4–8	1,200–1,400	1,400–1,600	1,400–1,800
Female	9–13	1,400–1,600	1,600–2,000	1,800–2,200
Female	14–18	1,800	2,000	2,400
Female	19–30	1,800–2,000	2,000–2,200	2,400
Female	31–50	1,800	2,000	2,200
Female	51+	1,600	1,800	2,000–2,200
Male	4–8	1,200–1,400	1,400–1,600	1,600–2,000
Male	9–13	1,600–2,000	1,800–2,200	2,000–2,600
Male	14–18	2,000–2,400	2,400–2,800	2,800–3,200
Male	19–30	2,400–2,600	2,600–2,800	3,000
Male	31–50	2,200–2,400	2,400–2,600	2,800–3,000
Male	51+	2,000–2,200	2,200–2,400	2,400–2,800

Table 7.3 Acceptable Macronutrient Distribution RangesSource: Institute of Medicine. 2005. *Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids*. Washington, DC: The National Academies Press. p.1325. Used under fair use guidelines.
Age	Carbohydrates (% of Calories)	Protein (% of Calories)	Fat (% of Calories)
Young Children (1–3)	45–65	5–20	30–40
Older children/adolescents (4–18)	45–65	10–30	25–35
Adults (19 and older)	45–65	10–35	20–35

Total Energy Expenditure (Output)

The amount of energy expended by a person in a day (total energy expenditure, TEE) is the sum of three categories of expenditures: 1. the kcal you burn while at rest (basal metabolism), 2. the kcal you burn when you digest food, and 3. the kcal you burn during physical activity (Figure 7.1).

Total Energy Expenditure = Basal Metabolism + Thermic Effect of Food + Physical Activity — Figure 7.1 Total energy expenditure is the sum of energy expended at rest, during digestion, and during physical activity. Credit: Human Nutrition, University of Hawai‘i at Mānoa Food Science and Human / CC BY 4.0 .

Basal metabolism includes the metabolic pathways necessary to support and maintain the body’s basic functions (e.g. breathing, heartbeat, liver and kidney function) while at rest. The basal metabolic rate (BMR) is the largest energy expenditure of the day – between 50 and 70 percent. Of all the organs, the liver requires the most energy (Table 7.4). Unfortunately, you cannot tell your liver to ramp up its activity level to expend more energy so you can lose weight. BMR is affected by body size, body composition, sex, age, nutritional status, and genetics. People with a larger frame size have a higher BMR simply because they have more mass. Muscle tissue burns more kcal than fat tissue even while at rest and thus the more muscle mass a person has, the higher their BMR. Since females typically have less muscle mass and a smaller frame size than men, their BMRs are generally lower than men’s. As we get older muscle mass declines and thus so does BMR. Body temperature and thyroid hormone levels also impact the BMR. Nutritional status also affects basal metabolism. Caloric restriction during dieting or starvation causes a decline in BMR; the body adapts by slowing down its basic functions – which certainly frustrates those who are dieting to lose weight!
The energy required for all the processes that take place during food digestion and absorption of nutrients is called the thermic effect of food (TEF). While some foods require more energy to process than others, the TEF for an average diet is approximately 10 percent of the kcals in the food.
The third category of energy expenditure, physical activity (PA) is variable. Depending on lifestyle, the energy expended in all physical movement, from blinking to running a marathon, ranges from 15 to 30 percent of total energy expended. The main control a person has over TEE is to increase physical activity.

Table 7.4 Energy Breakdown of Organs. Source: Energy and Protein Requirements. World Health Organization Technical Report Series 724. Updated 1991. Accessed May 10, 2026. Used under fair use guidelines.
Organ	Percent of Energy Expended
Liver	27
Brain	19
Heart	7
Kidneys	10
Skeletal muscle (at rest)	18
Other organs	19

How to Calculate Total Energy Expenditure

TEE is dependent on age, sex, height, weight, and physical activity level. Standardized formulas are derived from measurements of actual people. Several calculators are available. To estimate your TEE, record your daily activities and the time spent performing them. A spreadsheet for doing so is available online (https://www.cdc.gov/healthy-weight-growth/media/pdfs/physical_activity_diary_cdc.pdf). An interactive calculator is also available for use. (https://globalrph.com/medcalcs/estimated-energy-requirement-eer-equation/)

Attributions

Adapted by Pattie S. Green, Ph.D. and Jonathan E. Pottle, Ph.D., Tacoma Community College, from Human Nutrition, “Weight Management,” by University of Hawai‘i at Mānoa Food Science and Human Nutrition Program which is licensed under a Creative Commons Attribution 4.0 International License.

License

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Introduction to Human Nutrition: A Textbook for Tacoma Community College Students Copyright © 2026 by Pattie S. Green and Jonathan E. Pottle, Tacoma Community College is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.