rethinking energy balance facts you need to know.5

RETHINKING ENERGYBALANCE

Facts You Need to Know About Weight Lossand Management

by Melinda M. Manore, Ph.D., R.D., CSSD, FACSM

LEARNING OBJECTIVE

To introduce health and fitness professionals to the concept of

dynamic energy balance and new research showing key factors

that contribute to promoting weight management, weight loss/gain,

and overall health.

Key words:Weight Loss, Energy Intake, Dynamic Energy Balance,Exercise, Diet

INTRODUCTION

Most people think weight loss issimple. Eat less and move more!Although this statement captures

the general approach of weight loss programs, itcannot and doesn’t get at the many factors thatdetermine our body size and composition. It also

doesn’t get at why it is so difficult to lose weightand keep it off. This simple message typicallydoesn’t help your clients either. They have heard itmany times before. What they want to know iswhy weight loss is so difficult, why weight losschanges across time, and how to maintain weightloss once it is achieved.

Open any nutrition or exercise sciencetextbook and you will see the static energy

balance diagram, which states that changingone side of the energy balance equation morethan the other results in either weight gain orweight loss. This approach to energy balanceassumes that, when you change either energyintake or energy expenditure, the other side ofthe equation isn’t affected. Unfortunately, en-ergy balance isn’t that simple; it is dynamic,especially during periods of weight change(Table 1; Figure 1). Thus, when energy intakeis changed, energy expenditure also changes,even when no specific recommendations for

VOL. 19/ NO. 5 ACSM’s HEALTH & FITNESS JOURNALA 9

Copyright © 2015 American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.

changing energy expenditure are given. Exactly how changingone side of the energy balance equation influences the otherside can be very difficult to measure and/or predict.

Below are facts that will help you guide your clients throughweight loss and management and better answer their questions.

FACT 1: -3,500 KCALS m 1 LB BODY WEIGHT LOSSYou probably learned that a reduction of 3,500 kcals will result ina pound of weight loss. Where did this number come from? Doesit work for everyone regardless of body size and level of activity?

In 1958, Max Wishnofsky, M.D., reviewed the literature onweight loss in obese sedentary individuals who typicallyconsumed low-calorie, high-protein diets within a clinicalsetting. Under these conditions, he concluded that ‘‘the caloricequivalent of 1 lb of body weight lost is approximately 3,500kcals (21).’’ Across the years, we have transformed this numberinto a rule, without questioning whether it holds true for allindividuals regardless of body size, level of physical activity,age, sex, or genetics. We now know the number of kilocaloriesrequired for 1 lb of weight loss changes depending on how longthe dieting period lasts, what type of diet is fed, and whetherparticipants engage in physical activity. For example, re-searchers at the Pennington Biomedical Research Institute (6)examined weight loss in overweight men and women whodieted until they lost 15% of their body weight. They either

consumed a very-low-calorie diet (890 kcals per day) orreduced energy intake by 25%. Participants were not doingphysical activity. They found that, during the early phases ofweight loss (weeks 1 to 4), the energy equivalent for a pound ofweight loss was 2,208 kcals. However, as the diet extended toweeks 6 and beyond, the energy reduction required for a poundof weight loss approached Wishnofsky’s rule (Figure 1).Researchers hypothesized that, during the early phases ofweight loss, water, glycogen, protein, and fat are lost, whereastoward the later part of the diet, a greater percentageof weight loss is from fat. Adipose tissue is approximately85% fat (4), thus, the energy content of 1 lb of body fat isapproximately 3,470 kcals. Conversely, if the majority of theweight loss is caused by water, lean tissue, and glycogen losses,the energy content of these components is low. For example,the energy content of muscle, which is approximately 65% to70% water, is approximately 550 kcals per pound. Thus, theenergy content of weight loss will depend on the compositionof the weight loss and how the body is adapting to the energyrestriction placed on it. The impact of adding physical activityto an energy-restricted weight loss program also can change thecomposition of weight loss, energy substrates used, and howquickly weight loss occurs.

FACT 2: DURING PERIODS OF WEIGHT LOSS, ENERGYBALANCE IS DYNAMIC

During periods of weight loss, energy balance is dynamic V

not static. This fallacy is illustrated in the following example(17): A 75-kg man consumes an extra 100 kcals per day for 40years. The amount of extra energy consumed is equal to 1.46million kilocalories, with an estimated weight gain of 417 lbs(È190 kg) during the 40-year period (e.g., 1.46 million dividedby 3,500 kcals per pound). As a health professional, youintuitively know that this would not happen, yet how do youexplain the results? This static energy balance approach is

TABLE 1: Definitions of Static and DynamicEnergy BalanceStatic Energy Balance Approach: Assumes that a change in one side ofthe energy balance equation (e.g., energy intake) does not change orinfluence the other side of the equation (e.g., energy expenditure).

Dynamic Energy Balance Approach: Assumes that numerous biologicaland behavioral factors regulate and influence both sides of the energybalance equation. Thus, a change in one side of the equation (e.g.,energy intake) can and does influence the other side of the equation(e.g., energy expenditure).

Figure 1. Energy content of weight loss expressed as kilocalories per pound lost.

10 ACSM’s HEALTH & FITNESS JOURNALA | www.acsm-healthfitness.org VOL. 19/ NO. 5

Dynamic Energy Balance


assuming that, by changing the diet, no other components ofenergy balance changed, but this isn’t true. As extra energy isconsumed and weight is gained, energy expenditure wouldincrease. This weight gain increases the resting metabolic rate,which subsequently increases total energy expenditure becausethere is a greater energy cost in moving and maintaining alarger body. As one consistently consumes the extra 100 kcalsper day, body weight would increase until energy expenditureeventually balanced the increased demand for energy (e.g., theextra 100 kcals per day). Thus, the individual would eventuallybecome weight stable at a higher body weight, which mightrepresent a more realistic 6-lb (È2.7 kg) weight gain. However,to maintain this larger body size, the individual would need tocontinue to eat the extra 100 kcals per day. For any one person,the actual amount of weight gained will depend on a number ofindividual factors, including the extra kilocalories consumed,composition of the diet, body composition, type of exercise,and level of daily physical activity.

The concept of dynamic energy balance and some of the keyfactors that influence each side of the energy balance equationare illustrated in Figure 2. How each individual responds tochanges in each factor will depend on genetics, regulatoryhormones that control energy balance and appetite, gut health,and the food and exercise environment that can drive eating,exercise, and body composition. See Galgani and Ravussin (3)for more details on these factors.

FACT 3. PREDICTING WEIGHT LOSS DURING PERIODSOF ENERGY RESTRICTION IS DIFFICULT

Wishnofsky’s 3,500-kcals-per-pound rule is still reportedwidely in the research literature and used to predict weightloss for adults, regardless of body size or composition, level ofphysical activity, sex, or age. We now know that predictingweight loss or gain is not that simple. Researchers at theNational Institutes of Health (NIH) (5) and the PenningtonBiomedical Research Center (PBRC) (18) have spent yearsdeveloping mathematical models to better predict weightchange using the dynamic energy balance model. As onechanges energy intake or expenditure, these models take intoaccount changes in resting metabolic rate, body size, fat andlean tissue mass, voluntary physical activity, spontaneousphysical activity, the thermic effect of food, and the energycosts of fat and protein synthesis. For example, as you loseweight, body composition can change, which alters energyexpenditure. In addition, the energy cost of moving a smallerbody is less, thus, one has to work harder or longer to expendthe same amount of energy in physical activity compared withwhen one’s body weight was higher. These models calculatethese changes for you. Using the PBRC prediction model forweight change and data from well-controlled weight lossstudies (6,11), researchers showed that their model predictedwithin 2.2 kg of the actual weight loss, while using theWishnofsky’s rule, there was a 11-kg bias (19). However, it is

Figure 2. Key factors regulating and influencing energy balance.



important to remember that these prediction models weredeveloped using the results from weight loss studies withoverweight and obese individuals. If you are working withactive individuals who are leaner and capable of much higherlevels of exercise, you may need to adapt your results to fit yourclient’s unique characteristics. Regardless of their limitations,these models will help you do a better job of estimating the timerequired for weight changes to occur and provide your clientswith more realistic weight loss goals for a designated period.

These two prediction models are Web-based for simple use.Below is a brief description of each model:

• The NIH model (7) can be found at the NIH Web site: http://

bwsimulator.niddk.nih.gov. This model has two options: 1)

setting a goal weight or 2) indicating what diet and physical

activity changes you want to make to achieve a designated

weight loss or gain goal. Age, sex, height, and current body

weight and physical activity level are required. If the goal

weight option is selected, the goal weight and the number of

days to reach this weight goal are given. The calculator then

indicates how much of a change in energy intake or

expenditure are needed to reach the goal weight in the

designated time frame. The model provides the number of

calories needed to maintain the new body weight at the

designated level of physical activity. If the lifestyle change

option is selected, the diet and physical activity changes to be

made and the period are added. The model then predicts the

level of change required in each category to reach the goal.

• The Pennington model (18) can be found at the PBRC Web

site: https://www.pbrc.edu/research-and-faculty/calculators/.

This model requires that age, sex, height, and current weight

be entered, along with the daily energy-deficient (kilocalories

per day) goal. A graph and table then show how long it will

take to achieve the goal weight based on the energy deficit

entered. This Web site does not ask about current physical

activity level or how exercise energy expenditure may

change during the designated period. Because physical

activity is not part of this model, its application to active

individuals is limited.

FACT 4. DURING PERIODS OF ENERGY RESTRICTION,PROTEIN NEEDS INCREASE

When individuals restrict energy intake for weight loss, proteinintake typically decreases unless specific attention has beengiven to consuming more protein. During periods of energyrestriction, some proteins will be used for energy, depending onthe level of energy restriction and the type and amount ofphysical activity being performed. Thus, protein needs increasewith energy restriction, both absolute (grams per kilogram bodyweight per day) and relative amounts (percentage of total

energy from protein). The current Recommended DietaryAllowance for protein is 0.8 g/kg body weight per day or20% to 35% of total energy intake (8), with higher recommen-dations for active individuals (1.4-1.7 g/protein per kilogramper day) (12). During periods of energy restriction, the goal isto meet or exceed these same absolute levels of protein intaketo help preserve lean tissue. If energy is severely restricted and/or individuals are physically active, the need for proteinmay be even higher (10). For example, researchers placed20 healthy resistance-trained male athletes (body mass index,23 to 24 kg/m2) on an energy-restricted diet (60% of habitualenergy intake) (9). During this time, they were assignedrandomly to either a control (1 g/protein per kilogram bodyweight; n = 10) or treatment group (2.3 g/protein per kilogrambody weight; n = 10). Results showed that loss of lean masswas greater in the control group (-1.6 kg in 1 week) comparedwith that in the treatment group (-0.3 kg). Thus, the higherprotein intake (È35% of energy intake) helped preserve leantissue when energy intake was severely restricted for a shorttime. However, there currently are no data supporting intakeshigher than 2.5 g protein per kilogram per day when dieting forweight loss in the general population (10).

Timing of protein intake also is important especially ifphysical activity is included as part of the weight loss program.Spreading food and protein intake throughout the day ensuresthat adequate protein is available for building, repair, andmaintenance of lean tissue. In addition, higher protein dietshave been associated with increased satiety and reductions inenergy intake. For example, researchers fed 19 healthy




http://bwsimulator.niddk.nih.gov


https://www.pbrc.edu/research-and-faculty/calculators/

sedentary individuals (body mass index [BMI] range, 22.5 to30.1 kg/m2) three different diets in sequential order (20). First,they consumed a weight-maintaining diet for 2 weeks (energydistribution = 15% protein, 35% fat, and 50% carbohydrate).Second, they consumed an isocaloric diet (30% of energy fromprotein, 25% fat, and 50% carbohydrate) for 2 weeks. Finally,they were fed an ad libitum diet (energy distribution = 30%protein, 20% fat, and 50% carbohydrate) for 12 weeks. Whensubjects were allowed to eat ad libitum on the high-protein diet(30% of energy intake), they spontaneously decreased energyintake (-441 T 64 kcals per day) during the 12-week period. Thus,the higher protein diet was more satiating, leading to lower totalenergy intake, even while carbohydrate was held constant.

FACT 5. LOW-ENERGY DENSE FOOD ANDHIGH-INTENSITY EXERCISE CAN ALTER SATIETY

AND HUNGERChanging eating behaviors is one of the most difficultchallenges of any weight loss program; thus, a diet thatincreases satiety (fullness) could increase dietary adherence andpotentially successful weight loss (15). Research by Rolls et al.(14) at Pennsylvania State University shows that following alow-energy dense diet plan can increase satiety while loweringtotal energy intake. A low-energy dense diet is high in wholefruits and vegetables and whole grains and incorporates low-fatdairy, legumes/beans, and lean meats. Overall, the diet is lowerin fat and higher in fiber and water while reducing or

TABLE 2: Weight Management Facts: Key Points

Weight Management Facts Bottom Line

Fact 1: -3,500 kcals mmmmm 1 lb body weight loss. The number of kilocalories required for 1 lb of weight loss changes depending on how long thedieting period lasts, what type of diet is fed, and whether participants engage in physical activity.In one research study, this varied from 2,200 to 3,500 kcals per day (Figure 1).

Fact 2: During periods of weight loss, energybalance is dynamic.

The overconsumption of kilocalories will increase body weight if there is no change in overallenergy expenditure. However, as weight is gained, more energy is needed to maintain thelarger body. Weight will plateau as the increased energy expenditure matches the increasedenergy intake.

Fact 3. Predicting weight loss during periods ofenergy restriction is difficult.

Two mathematical models have been developed to help predict weight gain/loss based onchanges in lifestyle. NIH model: http://bwsimulator.niddk.nih.gov. Pennington model:https://www.pbrc.edu/research-and-faculty/calculators/.

Fact 4. During periods of energy restriction, proteinneeds increase.

If energy is restricted, protein intake should exceed the Recommended Dietary Allowance of0.8 g/kg body weight per day. Typical recommendations range from 1.4 to 1.7 g/protein perkilogram per day, similar to what is recommended to active individuals. There is no indicationthat a protein intake 92.5 g/kg body weight is necessary for the general population.

Fact 5. Low-energy dense diet can increase satiety. Following a low-energy dense diet plan can increase satiety while lowering total energy intake. Alow-energy dense diet is high in whole fruits and vegetables and whole grains and incorporateslow-fat dairy, legumes/beans, and lean meats.




https://www.pbrc.edu/research-and-faculty/calculators/

eliminating energy-containing beverages, especially sweetenedbeverages and alcohol. This type of eating pattern means thatan individual can consume a greater volume of food and feelsatisfied while overall energy intake is lower. The energydensity of a diet or a food is determined by measuring theamount of energy (kilocalories) for a given amount (grams) offood (kilocalories per gram). Evidence shows that a low-energydensity eating plan is effective at reducing energy intake,facilitating weight loss and prevention of weight regain, andmaintaining satiety in well-controlled feeding studies and infree-living conditions (2,13). Rolls et al. (1,16) have demon-strated the effectiveness of a low-energy density eating plan onenergy intake and weight loss. They found that by reducingenergy density by a designated amount (e.g., È25%) decreasesenergy intake by a similar percentage (23% to 24%; approx-imately -500 kcals per day deficit on a 2,000 kcals/day diet),yet participants reported similar levels of hunger and fullnessratings or enjoyment of the meals compared with controlconditions. Thus, reducing the energy density of the diet canreduce energy intake dramatically while still feeling satisfied. Akey component of a low-energy density eating plan is toincrease intake of foods high in water and fiber to promotesatiation while reducing both high-fat foods (i.e., potato chips,cheese, cookies) and low water and fiber foods (i.e., bakedtortilla chips, pretzels). This dietary approach can help yourclients better adhere to a healthier eating plan and lower energyintake, without counting calories.

Exercise type and intensity also can impact feelings ofhunger and lower energy intake after exercise. We now knowthat acute exercise, especially high-intensity exercise (960%VO2max), can suppress appetite by altering gut appetite-regulating hormones for 2 to 10 hours after exercise (7).However, research results are mixed and depend on subjectcharacteristics (e.g., body fatness, level of fitness, age, or sex)and exercise duration, intensity, type, and mode. Overall, inexercise-trained males, it seems that higher-intensity exerciseelicits suppression of gut appetite hormones, but studies inwomen are mixed (7). If appetite suppression does occur afterexercise, it can lower energy intake at the next meal andpotentially lower overall energy intake. Thus, encouraging yourclients to combine some higher-intensity exercise with a low-energy dense diet may help them manage hunger and reducetotal energy intake, especially if these two behaviors occurregularly throughout the week.

SUMMARYWeight loss is difficult. Thus, it is not surprising that many ofyour clients have been on numerous weight loss diets, withmixed results (Table 2). Understanding dynamic energy balanceand applying this approach to your weight management planswill help you and your clients make more realistic goals andapproaches for weight change. For weight loss, a reduction in

energy intake is extremely important, but unless the energydeficit is altered across time to account for changes in bodyweight, weight loss will slow and eventually stop. Predictingweight loss results based on changes in diet and exercise is nota precise science. New mathematical prediction models aredesigned to predict weight change more accurately, based onthe lifestyle changes implemented. During periods of energyrestriction, protein needs increase, especially if physical activityincreases. Thus, specific protein recommendations need toaccompany any weight loss diet. Research suggests that high-intensity exercise can blunt appetite after exercise and lowertotal daily energy intake, but more research is needed beforespecific recommendations can be given. Finally, helping yourclients eat a low-energy dense diet may not only help them loseweight and consume a healthier diet but also help them keepthe weight off once weight loss is achieved.

References1. Bell EA, Castellanos VH, Pelkman CL, Thorwart ML, Rolls BJ. Energy

density of foods affects energy intake in normal-weight women. Am JClin Nutr. 1998;67(3):412Y20.

2. Ello-Martin JA, Ledikwe JH, Rolls BJ. The influence of food portion sizeand energy density on energy intake: Implications for weight manage-ment. Am J Clin Nutr. 2005;82(1):236SY41S.

3. Galgani J, Ravussin E. Energy metabolism, fuel selection and bodyweight regulation. Int J Obesity (Lond). 2008;32(Suppl 7):S109Y19.

4. Gropper SS, Smith J. Advanced Nutrition and Human Metabolism.Belmont (CA): Wadsworth Cenagge Learning; 2013.

5. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect ofenergy imbalance on bodyweight. Lancet. 2011;378(9793):826Y37.

6. Heymsfield SB, Thomas D, Martin CK, et al. Energy content of weightloss: Kinetic features during voluntary caloric restriction. Metabolism.2012;61(7):937Y43.

7. Howe SM, Hand TM, Manore MM. Exercise-trained men and women:Role of exercise and diet on appetite and energy intake. Nutrients.2014;6(11):4935Y60.

8. Institute of Medicine, Food and Nutrition Board. Standing Committee onthe Scientific Evaluation of Dietary Intakes, National Research Council.Dietary Reference Intakes: Energy, Carbohydrate, Fiber, Fat, FattyAcids, Cholesterol, Protein, and Amino Acids. Washington (DC):National Academy Press; 2005.

9. Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces leanbody mass loss during weight loss in athletes. Med Sci Sports Exerc.2010;42(2):326Y37.

10. Phillips SM. A brief review of higher dietary protein diets in weight loss:A focus on athletes. Sports Med. 2014;44(Suppl 2):S149Y53.

11. Redman LM, Heilbronn LK, Martin CK, et al. Metabolic and behavioralcompensations in response to caloric restriction: implications for themaintenance of weight loss. PLoS ONE. 2009;4(2):e4377.

12. Rodriguez NR, DiMarco NM, Langley S; American Dietetic Association;Dietitians of Canada; American College of Sports Medicine: Nutritionand Athletic Performance. Position of the American Dietetic Association,Dietitians of Canada, and the American College of Sports Medicine:Nutrition and athletic performance. J Am Diet Assoc. 2009;109(3):509Y27.




13. Rolls BJ. The relationship between dietary energy density and energyintake. Physiol Behav. 2009;97(5):609Y15.

14. Rolls BJ. Plenary Lecture 1: Dietary strategies for the prevention andtreatment of obesity. Proc Nutr Soc. 2010;69(1):70Y9.

15. Rolls BJ. Dietary strategies for weight management. Nestle Nutr InstWorkshop Ser. 2012;73:37Y48.

16. Rolls BJ, Roe LS, Meengs JS. Reductions in portion size and energydensity of foods are additive and lead to sustained decreases in energyintake. Am J Clin Nutr. 2006;83(1):11Y7.

17. Swinburn B, Ravussin E. Energy balance or fat balance? Am J Clin Nutr.1993;57(Suppl. 5):766SY70S.

18. Thomas DM, Ciesla A, Levine JA, Stevens JG, Martin CK. Amathematical model of weight change with adaptation. Math BiosciEng. 2009;6(4):873Y87.

19. Thomas DM, Gonzalez MC, Pereira AZ, Redman LM, Heymsfield SB.Time to correctly predict the amount of weight loss with dieting. J AcadNutr Diet. 2014;114(6):857Y61.

20. Weigle DS, Breen PA, Matthys CC, et al. A high-protein diet inducessustained reductions in appetite, ad libitum caloric intake, and bodyweight despite compensatory changes in diurnal plasma leptin andghrelin concentrations. Am J Clin Nutr. 2005;82(1):41Y8.

21. Wishnofsky M. Caloric equivalents of gained or lost weight. Am J ClinNutr. 1958;6(5):542Y6.

Recommended Reading:Donnelly JE, Blair SN, Jakicic JM, Manore MM, Rankin JW, Smith BK.

Appropriate physical activity intervention strategies for weight lossand prevention of weight regain for adults. Med Sci Sports Exerc.2009;41(2):459.

Galgani J, Ravussin E. Energy metabolism, fuel selection and body weightregulation. Int J Obesity. 2008;32(Suppl. 7):S109Y19.

Manore MM. Weight management in the performance athlete. Nestle NutrInst Workshop Ser. 2013;75:123Y33.

Shook RP, Hand GA, Blair SN. Top 10 research questions related to energybalance. Res Q Exerc Sport. 2014;85(1):49Y58.

Sweat W, Manore MM. Dietary fiber: Simple steps for managing weight andimproving health. ACSM Health Fitness J. 2015;19(1),9Y16.

Sweat W, Manore MM. Too good to be true? Eating more and losing weightwith a low energy dense diet. ACSM Health Fitness J.2012;16(4),22Y8.

Disclosure: Author is funded currently by USDA NIFA Child-hood Obesity Prevention (no. 2013-67001-20418; no. 2011-68001-30020), OSU USDA AES and OSU USDA W2005Multistate Obesity Prevention. She has consulted for Clif Barand received honoraria from Gatorade Sports Science Institute.

Melinda M. Manore, Ph.D., R.D., CSSD,

FACSM, is a professor of Nutrition, College

of Public Health and Human Sciences at

Oregon State University. Her research

focuses on obesity and chronic disease

prevention, sport nutrition, and the energy

and nutritional needs of active individuals.

She is especially interested in the interactive role of diet and

exercise for energy balance and to achieve and maintain a

healthy sustainable weight.

BRIDGING THE GAP

Exercise and health professionals typically predict weightloss/gain for clients by using the static energy balancemodel, which does not apply during times of weightchange. They also assume that 3,500 kilocalories equals1 lb of weight loss/gain, which is not always true. Whenclients struggle to reach their designated weight goals, weoften assume that the client is not following the program.New mathematical models, which incorporate the dynamicenergy balance approach into their estimates of weightchange, will produce more realistic estimates of actualweight changes during periods of weight gain or loss.



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