Myths and Presumptions
Myth number 1: Small sustained changes in energy intake or expenditure will produce large, long-term weight changes.
Recent studies have shown that individual variability affects changes in body composition in response to changes in energy intake and expenditure, with analyses predicting substantially smaller changes in weight.
Myth number 2: Setting realistic goals for weight loss is important, because otherwise patients will become frustrated and lose less weight.
Although this is a reasonable hypothesis, empirical data indicate no consistent negative association between ambitious goals and program completion or weight loss. Indeed, several studies have shown that more ambitious goals are sometimes associated with better weight-loss outcomes.
Myth number 3: Large, rapid weight loss is associated with poorer long-term weight-loss outcomes, as compared with slow, gradual weight loss.
Within weight-loss trials, more rapid and greater initial weight loss has been associated with lower body weight at the end of long-term follow-up. Although it is not clear why some obese persons have a greater initial weight loss than others do, a recommendation to lose weight more slowly might interfere with the ultimate success of weight-loss efforts.
Myth number 4: It is important to assess the stage of change or diet readiness in order to help patients who request weight-loss treatment.
Readiness does not predict the magnitude of weight loss or treatment adherence among persons who sign up for behavioral programs or who undergo obesity surgery. The explanation may be simple — people voluntarily choosing to enter weight-loss programs are, by definition, at least minimally ready to engage in the behaviors required to lose weight.
Myth number 5: Physical-education classes, in their current form, play an important role in reducing or preventing childhood obesity.
Physical education, as typically provided, has not been shown to reduce or prevent obesity. There is almost certainly a level of physical activity (a specific combination of frequency, intensity, and duration) that would be effective in reducing or preventing obesity. Whether that level is plausibly achievable in conventional school settings is unknown, although the dose–response relationship between physical activity and weight warrants investigation in clinical trials.
Myth number 6: Breast-feeding is protective against obesity.
A World Health Organization (WHO) report states that persons who were breast-fed as infants are less likely to be obese later in life and that the association is “not likely to be due to publication bias or confounding.” Although existing data indicate that breast-feeding does not have important antiobesity effects in children, it has other important potential benefits for the infant and mother and should therefore be encouraged.
Myth number 7: A bout of sexual activity burns 100 to 300 kcal for each participant.
The energy expenditure of sexual intercourse can be estimated by taking the product of activity intensity in metabolic equivalents (METs), the body weight in kilograms, and time spent. For example, a man weighing 154 lb (70 kg) would, at 3 METs, expend approximately 3.5 kcal per minute (210 kcal per hour) during a stimulation and orgasm session. This level of expenditure is similar to that achieved by walking at a moderate pace (approximately 2.5 miles [4 km] per hour). Given that the average bout of sexual activity lasts about 6 minutes, a man in his early-to-mid-30s might expend approximately 21 kcal during sexual intercourse. Of course, he would have spent roughly one third that amount of energy just watching television, so the incremental benefit of one bout of sexual activity with respect to energy expended is plausibly on the order of 14 kcal.
Presumptions
Presumption number 1: Regularly eating (versus skipping) breakfast is protective against obesity.
Two randomized, controlled trials that studied the outcome of eating versus skipping breakfast showed no effect on weight in the total sample. However, the findings in one study suggested that the effect on weight loss of being assigned to eat or skip breakfast was dependent on baseline breakfast habits.
Presumption number 2: Early childhood is the period in which we learn exercise and eating habits that influence our weight throughout life.
Although a person’s BMI typically tracks over time (i.e., tends to be in a similar percentile range as the person ages), longitudinal genetic studies suggest that such tracking may be primarily a function of genotype rather than a persistent effect of early learning. No randomized, controlled clinical trials provide evidence to the contrary.
Presumption number 3: Eating more fruits and vegetables will result in weight loss or less weight gain, regardless of whether any other changes to one’s behavior or environment are made.
It is true that the consumption of fruits and vegetables has health benefits. However, when no other behavioral changes accompany increased consumption of fruits and vegetables, weight gain may occur or there may be no change in weight.
Presumption number 4: Weight cycling (i.e., yo-yo dieting) is associated with increased mortality.
Although observational epidemiologic studies show that weight instability or cycling is associated with increased mortality, such findings are probably due to confounding by health status. Studies of animal models do not support this epidemiologic association.
Presumption number 5: Snacking contributes to weight gain and obesity.
Randomized, controlled trials do not support this presumption. Even observational studies have not shown a consistent association between snacking and obesity or increased BMI.
Presumption number 6: The built environment, in terms of sidewalk and park availability, influences the incidence or prevalence of obesity.
According to a systematic review, virtually all studies showing associations between the risk of obesity and components of the built environment (e.g., parks, roads, and architecture) have been observational. Furthermore, these observational studies have not shown consistent associations, so no conclusions can be drawn.
Facts
- Although genetic factors play a large role, heritability is not a destiny; calculations show that moderate environmental changes can promote as much weight loss as the most efficacious pharmaceutical agents available.
- Diets (i.e., reduced energy intake) very effectively reduce weight, but trying to go on a diet or recommending that someone go on a diet generally does not work well in the long term.
- Regardless of body weight loss, an increased level of exercise increases health.
- Physical activity or exercise in a sufficient dose aids in long-term weight maintenance. Continuation of conditions that promote weight loss promotes maintenance of lower weight.
- For overweight children, programs that involve the parents and the home setting promote greater weight loss or maintenance.
- Provision of meals, and meal-replacement products promote greater weight loss.
- Some pharmaceutical agents can help patients achieve clinically meaningful weight loss and maintain the reduction as long as the agents continue to be used.
- In appropriate patients, bariatric surgery results in long-term weight loss and reduction in the rate of incidence in diabetes and mortality.
Myths, Presumptions, and Facts about Obesity
Authors: Krista Casazza, Ph.D., R.D., Kevin R. Fontaine, Ph.D., Arne Astrup, M.D., Ph.D., Leann L. Birch, Ph.D., Andrew W. Brown, Ph.D., Michelle M. Bohan Brown, Ph.D., Nefertiti Durant, M.D., M.P.H., +12, and David B. Allison.
Published: January 31, 2013 N Engl J Med 2013;368:446-454 DOI:10.1056/NEJMsa1208051 VOL. 368 NO. 5
REFERENCES
- Federal Trade Commission. Dietary supplements: an advertising guide for industry. April 2001
- Hill, AB. The environment and disease: association or causation? Proc R Soc Med 1965;58:295-300
- Taubes, G. Epidemiology faces its limits. Science 1995;269:164-169
- Fairman, KA. Why hypotheses informed by observation are often wrong: results of randomized controlled trials challenge chronic disease management strategies based on epidemiological evidence. J Manag Care Pharm 2011;17:224-231
- Hall, KD. Predicting metabolic adaptation, body weight change, and energy intake in humans. Am J Physiol Endocrinol Metab 2010;298:E449-66
- Thomas, DM, Martin, CK, Heymsfield, S, Redmon, LM, Schoeller, DA, Levine, JA. A simple model predicting individual weight change in humans. J Biol Dyn 2011;5:579-599
- Thomas, DM, Schoeller, DA, Redman, LA, Martin, CK, Levine, JA, Heymsfield, SB. A computational model to determine energy intake during weight loss. Am J Clin Nutr 2010;92:1326-1331
- Linde, JA, Jeffery, RW, Levy, RL, Pronk, NP, Boyle, RG. Weight loss goals and treatment outcomes among overweight men and women enrolled in a weight loss trial. Int J Obes (Lond) 2005;29:1002-1005
- Astrup, A, Rossner, S. Lessons from obesity management programmes: greater initial weight loss improves long-term maintenance. Obes Rev 2000;1:17-19
- Nackers, LM, Ross, KM, Perri, MG. The association between rate of initial weight loss and long-term success in obesity treatment: does slow and steady win the race? Int J Behav Med 2010;17:161-167
- Fontaine, KR, Wiersema, L. Dieting readiness test fails to predict enrollment in a weight loss program. J Am Diet Assoc 1999;99:664-664
- Kriemler, S, Zahner, L, Schindler, C, et al. Effect of school-based physical activity programme (KISS) on fitness and adiposity in primary schoolchildren: cluster randomised controlled trial. BMJ 2010;340:c785-c785
- Dobbins, M, De Corby, K, Robeson, P, Husson, H, Tirilis, D. School-based physical activity programs for promoting physical activity and fitness in children and adolescents aged 6-18. Cochrane Database Syst Rev 2009;1:CD007651-CD007651
- Horta BL, Bahl R, Martinés JC, Victora CG. Evidence of the long-term effects of breastfeeding: systematic reviews and meta-analyses. Geneva: World Health Organization, 2007.
- Casazza, K, Fernandez, JR, Allison, DB. Modest protective effects of breast-feeding on obesity: is the evidence truly supportive? Nutr Today 2012;47:33-38
- Kramer, MS, Matush, L, Vanilovich, I, et al. Effects of prolonged and exclusive breastfeeding on child height, weight, adiposity, and blood pressure at age 6.5 y: evidence from a large, randomized trial. Am J Clin Nutr 2007;86:1717-1721
- Gillman, MW. Breastfeeding and obesity — the 2011 scorecard. Int J Epidemiol 2011;40:681-684
- Jette, M, Sidney, K, Blumchen, G. Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity. Clin Cardiol 1990;13:555-565
- Bohlen, JG, Held, JP, Sanderson, MO, Patterson, RP. Heart rate, rate-pressure product, and oxygen uptake during four sexual activities. Arch Intern Med 1984;144:1745-1748
- Schlundt, DG, Hill, JO, Sbrocco, T, Pope-Cordle, J, Sharp, T. The role of breakfast in the treatment of obesity: a randomized clinical trial. Am J Clin Nutr 1992;55:645-651
- Brisbois, TD, Farmer, AP, McCargar, LJ. Early markers of adult obesity: a review. Obes Rev 2012;13:347-367
- Rolls, BJ, Ello-Martin, JA, Tohill, BC. What can intervention studies tell us about the relationship between fruit and vegetable consumption and weight management? Nutr Rev 2004;62:1-17
- Vasselli, JR, Weindruch, R, Heymsfield, SB, et al. Intentional weight loss reduces mortality rate in a rodent model of dietary obesity. Obes Res 2005;13:693-702
- Whybrow, S, Mayer, C, Kirk, TR, Mazlan, N, Stubbs, RJ. Effects of two weeks’ mandatory snack consumption on energy intake and energy balance. Obesity (Silver Spring) 2007;15:673-685
- Ferdinand, A, Sen, B, Rahurkar, S, Engler, S, Menachemi, N. The relationship between built environments and physical activity: a systematic review. Am J Public Health 2012;102:e7-e13
- Hewitt, JK. The genetics of obesity: what have genetic studies told us about the environment. Behav Genet 1997;27:353-358
- Heymsfield, SB. Energy intake: reduced as prescribed? Am J Clin Nutr 2011;94:3-4
- Carroll, S, Dudfield, M. What is the relationship between exercise and metabolic abnormalities? A review of the metabolic syndrome. Sports Med 2004;34:371-418
- Wu, T, Gao, X, Chen, M, van Dam, RM. Long-term effectiveness of diet-plus-exercise interventions vs. diet-only interventions for weight loss: a meta-analysis. Obes Rev 2009;10:313-323
- Middleton, KM, Patidar, SM, Perri, MG. The impact of extended care on the long-term maintenance of weight loss: a systematic review and meta-analysis. Obes Rev 2012;13:509-517
- McLean, N, Griffin, S, Toney, K, Hardeman, W. Family involvement in weight control, weight maintenance and weight-loss interventions: a systematic review of randomised trials. Int J Obes Relat Metab Disord 2003;27:987-1005
- Wing, RR, Jeffery, RW. Food provision as a strategy to promote weight loss. Obes Res 2001;9:Suppl 4:271S-275S
- Wright, SM, Aronne, LJ. Obesity in 2010: the future of obesity medicine: where do we go from here? Nat Rev Endocrinol 2011;7:69-70
