11.3: Balancing Energy Input with Energy Output

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Learning Objectives

• Estimate your daily 
  energy
   requirement.
• Define 
  basal metabolism
   and explain the factors that affect basal metabolic rate.
• Summarize why the amount of food we eat (appetite) is not completely under our conscious control.

Energy

 Intake Balances 

Energy

 Output To Maintain Weight

Recall that the 

macronutrients

 you consume are either converted to 

energy

, stored, or used to synthesize macromolecules. A nutrient’s metabolic path is dependent upon 

energy balance

. When you are in a positive 

energy balance

 the excess nutrient 

energy

 will be stored or used to grow (e.g., during childhood, pregnancy, and wound healing). When you are in negative 

energy balance

 you aren’t taking in enough 

energy

 to meet your needs, so your body will need to use its stores 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

, lost when it is in negative 

energy balance

, and gained when it is in positive 

energy balance

. In general, weight is a good predictor of 

energy balance

, but many other factors play a role in 

energy

 intake and 

energy

 expenditure. Some of these factors are under your control and others are not. Let us begin with the basics on how to estimate 

energy

 intake, 

energy

 requirement, and 

energy

 output. Then we will consider the other factors that play a role in maintaining 

energy balance

 and hence, body weight.

Estimating 

Energy

 Requirement

To maintain body weight you have to balance the calories obtained from food and beverages with the calories expended every day. Here, we will discuss how to calculate your 

energy

 needs in kilocalories per day so that you can determine whether your caloric intake falls short, meets, or exceeds your 

energy

 needs. The Institute of Medicine has devised a formula for calculating your 

Estimated Energy Requirement (EER)

. It takes into account your age, sex, weight, height, and physical activity level (PA). The EER is a standardized mathematical prediction of a person’s daily 

energy

 needs in kilocalories per day required to maintain weight. It is calculated via the following formulas:

• Adult male:
  EER=662−[9.53×age(y)]+PA×[15.91×wt(kg)+5.39.6×ht(m)](11.3.1)$$\begin{array}{}\text{(11.3.1)}& \text{EER}=662-[9.53\times age(y)]+PA\times [15.91\times wt(kg)+\mathrm{5.39.6}\times ht(m)]\end{array}$$
• Adult female:
  EER=354−[6.91×age(y)]+PA×[9.36×wt(kg)+726×ht(m)(11.3.2)$$\begin{array}{}\text{(11.3.2)}& \text{EER}=354-[6.91\times age(y)]+PA\times [9.36\times wt(kg)+726\times ht(m)\end{array}$$

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.

Interactive

To begin your dietary assessment, go to MyPlate, which is available on the US Department of Agriculture (USDA) website: http://www.choosemyplate.gov/.

Table 11.3.1$\mathrm{11.3.}1$: Physical Activity (PA) Categories and Values

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
These values only apply to normal weight adults and not to children or pregnant or lactating women. Source: Health Canada. “Dietary Reference Intake Tables.” Last modified November 29, 2010. http://www.hc-sc.gc.ca/fn-an/nutrition/reference/table/index-eng.php#eeer.

The numbers within the equations for the EER were derived from measurements taken from a group of people of the same sex and age with similar body size and physical activity level. These standardized formulas are then applied to individuals whose measurements have not been taken, but who have similar characteristics in order to estimate their 

energy

 requirements. Thus, a person’s EER is, as the name suggests, an estimate for an average person of similar characteristics. EER values are different for children, pregnant or lactating women, and for overweight and 

obese

 people. Also, remember the EER is calculated based on weight maintenance, not for weight loss or weight gain.

Table 11.3.2$\mathrm{11.3.}2$: Estimated Daily 

Calorie

 Needs

Sex	Age (years)	Sedentary	Moderately Active	Active
Child (female and male)	2–3	1,000–1,200	1,000–1,400	1,000–1,400
Female	4–8	1,200–1,400	1,400–1,600	1,400–1,800
	9–13	1,400–1,600	1,600–2,000	1,800–2,200
	14–18	1,800	2,000	2,400
	19–30	1,800–2,000	2,000–2,200	2,400
	31–50	1,800	2,000	2,200
	51+	1,600	1,800	2,000–2,200
Male	4–8	1,200–1,400	1400–1,600	1,600–2,000
	9–13	1,600–2,000	1,800–2,200	2,000–2,600
	14–18	2,000–2,400	2,400–2,800	2,800–3,200
	19–30	2,400–2,600	2,600–2,800	3,000
	31–50	2,200–2,400	2,400–2,600	2,800–3,000
	51+	2,000–2,200	2,200–2,400	2,400–2,800

Source: US Department of Agriculture. 2010 Dietary Guidelines for Americans. 2010. http://health.gov/dietaryguidelines/dga2010/DietaryGuidelines2010.pdf.

The 2010 Dietary Guidelines provides a table (Table 11.3.2$\mathrm{11.3.}2$) that gives the estimated daily 

calorie

 needs for different age groups of males and females with various activity levels. The 2010 Dietary Guidelines also states that while knowing the number of calories you need each day is useful, it is also pertinent to obtain your calories from 

nutrient-dense foods

 and consume the various 

macronutrients

 in their Acceptable Macronutrient Distribution Ranges (AMDRs) (Table 11.3.3$\mathrm{11.3.}3$).

Table 11.3.3$\mathrm{11.3.}3$: Acceptable Macronutrient Distribution Ranges

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

Source: Institute of Medicine. “Dietary Reference Intakes: 

Macronutrients

.” Dietary Reference Intakes for 

Energy

, Carbohydrate. Fiber, Fat, 

Fatty Acids

, Cholesterol, Protein, and 

Amino Acids

. September 5, 2002. www.iom.edu/~/media/Files/Act...onutrients.pdf

Total 

Energy

 Expenditure (Output)

The amount of 

energy

 you expend every day includes not only the calories you burn during physical activity, but also the calories you burn while at rest (

basal metabolism

), and the calories you burn when you digest food. The sum of caloric expenditure is referred to as total 

energy

 expenditure (TEE). 

Basal metabolism

 refers to those 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 amount of 

energy

 required by the body to conduct its basic functions over a certain time period. The great majority of 

energy

 expended (between 50 and 70 percent) daily is from conducting life’s basic processes. Of all the 

organs

, the liver requires the most 

energy

 (Table 11.3.4$\mathrm{11.3.}4$). Unfortunately, you cannot tell your liver to ramp up its activity level to expend more 

energy

 so you can lose weight. BMR is dependent on 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 calories 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. Nutritional status also affects 

basal metabolism

. Caloric restriction, as occurs while dieting, for example, causes a decline in BMR. This is because the body attempts to maintain homeostasis and will adapt by slowing down its basic functions to offset the decrease in 

energy

 intake. Body temperature and thyroid hormone levels are additional determinants of BMR.

Table 11.3.4$\mathrm{11.3.}4$: 

Energy

 Breakdown of 

Organs

Organ	Percent of  Energy  Expended
Liver	27
Brain	19
Heart	7
Kidneys	10
Skeletal muscle (at rest)	18
Other  organs	19

The 

energy

 required for all the enzymatic reactions that take place during food digestion and absorption of 

nutrients

 is called the “thermic effect of food” and accounts for about 10 percent of total 

energy

 expended per day. The other 

energy

 required during the day is for physical activity. Depending on 

lifestyle

, the 

energy

 required for this ranges between 15 and 30 percent of total 

energy

 expended. The main control a person has over TEE is to increase physical activity.

Figure 11.3.1$\mathrm{11.3.}1$: Total 

energy

 expenditure is the sum of 

energy

 expended at rest, during digestion, and during physical activity.

How to Calculate Total 

Energy

 Expenditure

Calculating TEE can be tedious, but has been made easier as there are now calculators available on the Web. TEE is dependent on age, sex, height, weight, and physical activity level. The equations are based on standardized formulas produced from actual measurements on groups of people with similar characteristics. To get accurate results from web-based TEE calculators, it is necessary to record your daily activities and the time spent performing them. A spreadsheet for doing so is available online at http://www.health-calc.com/Calculate_daily_energy_expenditure.pdf.

Interactive 11.4: Health-calc.com offers an interactive TEE calculator.

http://www.health-calc.com/diet/

energy

-expenditure-advanced

Factors Affecting 

Energy

 Intake

Physiology

In the last few decades scientific studies have revealed that how much we eat and what we eat is controlled not only by our own desires, but also is regulated physiologically and influenced by genetics. The hypothalamus in the brain is the main control point of appetite. It receives hormonal and neural signals, which determine if you feel hungry or full. Hunger is an unpleasant sensation of feeling empty that is communicated to the brain by both mechanical and chemical signals from the periphery. Conversely, 

satiety

 is the sensation of feeling full and it also is determined by mechanical and chemical signals relayed from the periphery. The hypothalamus contains distinct centers of neural circuits that regulate hunger and 

satiety

 (Figure 11.3.2$\mathrm{11.3.}2$).

Figure 11.3.2$\mathrm{11.3.}2$: This is a scan of a brain. The hypothalamus contains distinct centers of neural circuits that regulate hunger and 

satiety

. Source: Diabesity, Sixth Framework Programme. “Novel Molecular Targets for 

Obesity

 and 

Type 2 Diabetes

.” 2002-2006. www.diabesity.eu/.honours.htm.

Hunger pangs are real and so is a “growling” stomach. When the stomach is empty it contracts, producing the characteristic pang and “growl.” The stomach’s mechanical movements relay neural signals to the hypothalamus, which relays other neural signals to parts of the brain. This results in the conscious feeling of the need to eat. Alternatively, after you eat a meal the stomach stretches and sends a neural signal to the brain stimulating the sensation of 

satiety

 and relaying the message to stop eating. The stomach also sends out certain 

hormones

 when it is full and others when it is empty. These 

hormones

 communicate to the hypothalamus and other areas of the brain either to stop eating or to find some food.

Fat tissue also plays a role in regulating food intake. Fat tissue produces the hormone leptin, which communicates to the 

satiety

 center in the hypothalamus that the body is in positive 

energy balance

. The discovery of leptin’s functions sparked a craze in the research world and in the diet pill industry as it was hypothesized that if you give leptin to a person who is overweight, they will decrease their food intake. Alas, this is not the case. In several clinical trials it was found that people who are overweight or 

obese

 are actually resistant to the hormone, meaning their brain does not respond as well to it.Dardeno, T. A. et al. “Leptin in Human Physiology and Therapeutics.” Front Neuroendocrinol 31, no. 3 (2010): 377–93. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2916735/?tool=pubmed. Therefore, when you administer leptin to an overweight or 

obese

 person there is no sustained effect on food intake.

Nutrients

 themselves also play a role in influencing food intake. The hypothalamus senses nutrient levels in the blood. When they are low the hunger center is stimulated, and when they are high the 

satiety

 center is stimulated. Furthermore, cravings for salty and sweet foods have an underlying physiological basis. Both undernutrition and overnutrition affect hormone levels and the neural circuitry controlling appetite, which makes losing or gaining weight a substantial physiological hurdle.

Genetic Influences

Genetics certainly play a role in body fatness and weight and also affects food intake. Children who have been adopted typically are similar in weight and body fatness to their biological parents. Moreover, identical twins are twice as likely to be of similar weights as compared to fraternal twins. The scientific search for 

obesity

 genes is ongoing and a few have been identified, such as the gene that encodes for leptin. However, overweight and 

obesity

 that manifests in millions of people is not likely to be attributed to one or even a few genes, but to rather the interactions of hundreds of genes with the environment. In fact, when an individual has a mutated version of the gene coding for leptin, they are 

obese

, but only a few dozen people around the world have been identified as having a completely defective leptin gene.

Psychological/Behavioral Influences

When your mouth waters in response to the smell of a roasting Thanksgiving turkey and steaming hot pies, you are experiencing a psychological influence on food intake. A person’s perception of good-smelling and good-tasting food influences what they eat and how much they eat. Mood and emotions are associated with food intake. Depression, low self-esteem, compulsive disorders, and emotional trauma are sometimes linked with increased food intake and 

obesity

.

Certain behaviors can be predictive of how much a person eats. Some of these are how much food a person heaps onto their plate, how often they snack on 

calorie

-dense, salty foods, how often they watch television or sit at a computer, and how often they eat out. A study published in a 2008 issue of 

Obesity

 looked at characteristics of Chinese buffet patrons. The study found that those who chose to immediately eat before browsing the buffet, used larger plates, used a fork rather than chopsticks, and chewed less per bite of food, had higher BMIs than patrons who did not exhibit these behaviors.Levin, B. E. “Developmental Gene X Environment Interactions Affecting Systems Regulating 

Energy

 Homeostasis and 

Obesity

.” Front Neuroendocrinol 3 (2010): 270–83. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903638/?tool=pubmed. Of course many behaviors are reflective of what we have easy access to—a concept we will discuss next.

Societal Influences

It is without a doubt that the American society affects what and how much we eat. Portion sizes have increased dramatically in the past few decades. For example, a bagel is now more than twice the size it was in the 1960s. Today, American teenagers have access to a massive amount of 

calorie

-dense foods and beverages, which is a large contributor to the recent rapid increase in overweight and 

obesity

 in adolescents in this country. Even different cultures within the United States have different eating habits. For instance, southern Americans, in general, consume more foods high in fat, which is a contributing factor to their higher incidences of overweight and 

obesity

 than Americans who live in the northern states. (Alaska is an exception because it also has a high incidence of overweight and 

obesity

, which is also partly attributed to diet.)

The fast food industry in America not only supplies Americans with a large proportion of their diet, but because of its massive presence in society dominates the workings of the entire food system. To generalize, most fast food items have little nutritional merit as they are highly processed and rich in saturated fat, salt, and 

added sugars

. Despite fast foods being a poor source of nourishment, Americans spend over one hundred billion dollars per year on fast food, up from six billion dollars in the early 1970s. The fast food business is likely to continue to grow in North America (and the rest of the world) and greatly affect the diets of whole populations. Because it is unrealistic to say that Americans should abruptly quit eating fast food to save their health (because they will not) society needs to come up with ideas that push nutrient-dense whole foods into the fast food industry. You may have observed that this largely consumer-driven push is having some effect on the foods the fast food industry serves (just watch a recent Subway commercial, or check the options now available in a McDonald’s Happy Meal). Pushing the fast food industry to serve healthier foods is a realistic and positive way to improve the American diet.

Video 11.3.1$\mathbf{11.3.}\mathbf{1}$: History, Structure, and Ethics of the Fast Food Industry (click to see video) A brief clip about the fast food industry and its effect on the United States.

Tools for Change

Support the consumer movement of pushing the fast food industry and your favorite local restaurants into serving more 

nutrient-dense foods

. You can begin this task by starting simple, such as requesting extra tomatoes and lettuce on your burger and more nutrient-dense choices in the salad bar. Also, choose their low-

calorie

 menu options and help support the emerging market of healthier choices in the fast food industry. In today’s fast-paced society, it is difficult for most people to avoid fast food all the time. When you do need a quick bite on the run, choose the fast food restaurants that serve healthier foods. Also, start asking for caloric contents of foods so that the restaurant becomes more aware that their patrons are being 

calorie

 conscious.

Factors Affecting 

Energy

 Expenditure

Physiological and Genetic Influences

Why is it so difficult for some people to lose weight and for others to gain weight? One theory is that every person has a “set point” of 

energy balance

. This set point can also be called a fat-stat or lipostat, meaning the brain senses body fatness and triggers changes in 

energy

 intake or expenditure to maintain body fatness within a target range. Some believe that this theory provides an explanation as to why after dieting, most people return to their original weight not long after stopping the diet. Another theory is referred to as the “settling” point system, which takes into account (more so than the “set-point” theory) the contribution of the obesogenic environment to weight gain. In this model, the reservoir of body fatness responds to 

energy

 intake or 

energy

 expenditure, such that if a person is exposed to a greater amount of food, body fatness increases, or if a person watches more television body fatness increases. A major problem with these theories is that they overgeneralize and do not take into account that not all individuals respond in the same way to changes in food intake or 

energy

 expenditure. This brings up the importance of the interactions of genes and the environment.

Not all individuals who take a weight-loss drug lose weight and not all people who smoke are thin. An explanation for these discrepancies is that each individual’s genes respond differently to a specific environment. Alternatively, environmental factors can influence a person’s gene profile, which is exemplified by the effects of the prenatal environment on body weight and fatness and 

disease

 incidence later in life. One of the first scientific investigations of prenatal control over 

energy balance

 was conducted in Germany. In this observational study, scientists found that offspring born to mothers who experienced famine were more likely to be 

obese

 in adulthood than offspring born to mothers who were pregnant just after World War II who lived in the same geographical locations.Matthews, C. E. “Amount of Time Spent in Sedentary Behaviors in the United States, 2003–2004.” Am J Epidemiol 167, no. 7 (2008): 875–81. doi: 10.1093/aje/kwm390. Other studies have shown that the offspring of women who were overweight during pregnancy have a greater propensity for being overweight and for developing 

Type 2 diabetes

. Thus, undernutrition and overnutrition during pregnancy influence body weight and 

disease

 risk for offspring later in life. They do so by adapting 

energy metabolism

 to the early nutrient and hormonal environment in the womb.

Audio Link 11.1: Rethinking Thin - The Myths and Realities of Dieting

Listen to this NPR broadcast for scientific information about why it is so difficult for some people to lose weight.

Psychological/Behavioral Influence

Sedentary behavior

 is defined as the participation in the pursuits in which 

energy

 expenditure is no more than one-and-one-half times the amount of 

energy

 expended while at rest and include sitting, reclining, or lying down while awake. Of course, the sedentary 

lifestyle

 of many North Americans contributes to their average 

energy

 expenditure in daily life. Simply put, the more you sit, the less 

energy

 you expend. A study published in a 2008 issue of the American Journal of Epidemiology reports that 55 percent of Americans spend 7.7 hours in 

sedentary behavior

 daily.Matthews, C. E. “Amount of Time Spent in Sedentary Behaviors in the United States, 2003–2004.” Am J Epidemiol 167, no. 7 (2008): 875–81. doi: 10.1093/aje/kwm390. Fortunately, including only a small amount of low-level physical activity benefits weight control. A study published in the June 2001 issue of the International Journal of Behavioral Nutrition and Physical Activity reports that even breaking up sitting-time with frequent, but brief increased 

energy

 expenditure activities, such as walking for five minutes every hour, helps maintain weight and even aids in weight loss.Wu, Y. “Overweight and 

Obesity

 in China.” Br Med J 333, no. 7564 (2006): 362. doi: 10.1136/bmj.333.7564.362. Americans partake in an excessive amount of screen time, which is a 

sedentary behavior

 that not only reduces 

energy

 expenditure, but also contributes to weight gain because of the exposure to aggressive advertising campaigns for unhealthy foods.

Societal Influence

In the United States, many societal factors influence the number of calories burned in a day. Escalators, moving walkways, and elevators (not to mention cars!) are common modes of transportation that reduce average daily 

energy

 expenditure. Office work, high-stress jobs, and occupations requiring extended working hours are all societal pressures that reduce the time allotted for exercise of large populations of Americans. Even the remote controls that many have for various electronic devices in their homes contribute to the US society being less active. More “obesogenic” factors were discussed in the opening of this chapter.

Socioeconomic status

 has been found to be inversely proportional to weight gain. One reason for this relationship is that inhabitants of low-income neighborhoods have reduced access to safe streets and parks for walking. Another is that fitness clubs are expensive and few are found in lower-income neighborhoods. The recent and long-lasting economic crisis in this country is predicted to have profound effects on the average body weight of Americans. The number of homeless in this country is rising with many children and adults living in hotels and cars. As you can imagine neither of these “home spaces” has a kitchen, making it impossible to cook nutritious meals and resulting in increased economically-forced access to cheap, unhealthy foods, such as that at a nearby gas station.

Key Takeaways

Energy balance

 is achieved when 

energy

 intake is equal to 

energy

 expended. 

Energy balance

 is essential for maintaining weight. Knowing the number of calories you need each day is a useful reference point, but it is also important to obtain your calories from 

nutrient-dense foods

 and consume the 

macronutrients

 in their AMDRs. The amount of 

energy

 you expend every day includes not only the calories you burn during physical activity, but also the calories you burn at rest (

basal metabolism

), and the calories you burn when you digest food. Basal metabolic rate (BMR) is dependent on body size, body composition, sex, age, nutritional status, genetics, body temperature, and thyroid hormone levels. The great majority of 

energy

 expended (between 50 and 70 percent) daily comes from conducting life’s basic processes. The main control a person has over TEE is to increase physical activity. 

Energy

 intake is regulated by complex physiological responses and is influenced by genetics, behavior, and society. 

Energy

 expenditure is also regulated by complex physiological responses and is influenced by genetics, behavior, and society.

Discussion Starters

1. Some types of transportation are becoming economically unfeasible for 
   obese
    people. Discuss whether or not it is acceptable that air carriers can enforce that 
   obese
    people (or what they politely call “passengers of size” or “passengers requiring extra space”) pay more for their seats.
2. Many people have a hard time understanding the difficulties of being too skinny. Discuss with your peers how to empathize with the weight problems of underweight people. Read the article to understand that being skinny does not mean a person necessarily has a lower risk of chronic 
   disease
   . http://www.msnbc.msn.com/id/18594089/ns/health-fitness/t/thin-people-can-be-fat-inside/