February 13, 2013
With more than half of U.S. adults on a diet at any given time, it is no surprise that myriad weight-loss tips, plans and gimmicks pervade the Internet, bookstores and dinner conversations. It is difficult for even the most discerning and highly educated health, fitness and nutrition professionals to weed through the massive amount of available information to discern fact from fiction. In fact, even some of the most widely accepted beliefs about weight loss, espoused by leading experts and advocates, may not even be true. Now, a group of academicians have published a paper on the topic in The New England Journal of Medicine (NEJM). They divided common weight-loss beliefs into myths, presumptions and facts. Here is a recap of what they had to say:
Myths: “Beliefs held to be true despite substantial refuting evidence”
“Small sustained changes in energy balance (“eat less, exercise more”) will lead to large, long-term weight loss.”
- The notion that the small changes add up to big results is false, the study authors say. Cringe. To inspire hope and the intrinsic motivation to keep going, even when change is slow, many experts frequently advise clients to make small changes—“Just eat 250 calories less and burn 250 calories more per day to lose 1 pound per week,” or “What comes off slow, stays off longer.” Over time, those small changes are supposed to add up to meaningful weight loss. Not so, according to the scientific evidence, the authors say.
- The study authors remind us that the 3,500-calories-equals-1-pound rule is based on short-term studies in men on very-low-calorie diets. It may hold true early on, but it does not hold true indefinitely. After an initial weight loss, the pounds come off much slower. The authors provide the example that the 3,500-kcal rule predicts that a 100-calorie deficit per day will lead to a 50-pound weight loss in five years, but the true weight loss is only about 10 pounds. This is mostly because weight loss is typically accompanied by loss of muscle mass and subsequent decreased metabolism.
“Setting realistic goals for weight loss is important, because otherwise patients will become frustrated and lose less weight.”
- Read any book on health-education strategies, and setting SMART (Specific, Measurable, Attainable, Relevant and Time-bound) goals is a basic and essential element of behavioral change. But according to the research cited in this paper, ambitious (and arguably unrealistic) goals are sometimes associated with more dramatic weight loss, and setting realistic goals is not associated with improved weight loss.
“Large, rapid weight loss is associated with poor long-term weight-loss outcomes, as compared with slow, gradual weight loss.”
- “Slow and steady wins the race,” right? Maybe not. Studies show that more rapid and greater initial weight loss is associated with lower body weight at the end of short-term and, in some cases, long-term follow-up. Of course, research studies are just a sampling of what happens in the real world. But based on the evidence available, the authors warn that giving the advice to lose weight more slowly may interfere with the success of a client’s weight-loss efforts.
“It is important to assess the stage of change or diet readiness in order to help patients who request weight-loss treatment.”
- If setting SMART goals is the first premise of behavior-change counseling, assessing readiness to change is premise “zero.” Before embarking on a journey to help someone lose weight, you have to understand if they are really interested and committed to the task. Otherwise, both of you are wasting your time. It turns out that the science says that a client’s stage of change is not associated with weight loss, presumably because anyone willing to sign up for a weight-loss program is ready to change.
“Physical education classes, in their current form, play an important role in reducing or preventing childhood obesity.”
- There have been widespread calls to action to increase the amount of physical education (PE) in the school child’s day in an effort to accumulate more minutes towards the goal of 60 minutes per day of moderate-to-vigorous physical activity. But even if every school offered PE classes every day, the research to date suggests that it will not lead to changes in body mass index. Of course, that may likely be due to the fact that the average PE class does little to increase minutes of moderate-to-vigorous activity for most kids.
“Breastfeeding is protective against obesity.”
- The long list of frequently cited benefits of breastfeeding includes decreased risk of obesity in the infant. It turns out that the World Health Organization, one of the biggest proponents for breastfeeding and who published a report indicating that breastfeeding protect against obesity, found significant publication bias in the literature it reviewed. (Publication bias occurs when studies with positive findings are published and disseminated and those with negative findings are not published.) The evidence offers many valid health benefits related to breastfeeding for both infant and mother, but protection from obesity is likely not one of them, the authors write.
“A bout of sexual activity burns 100 to 300 calories.”
- Sex may be the workout of choice for many people, but they should not count on it to burn calories and contribute to weight loss. The researchers point out that an average bout of sexual activity lasts about six minutes—equivalent to a 21-calorie energy expenditure for the average man in his 30s (the average woman’s calorie expenditure is even less). That’s only 14 calories more than he would spend watching TV.
Presumptions: “Beliefs held to be true for which convincing evidence does not yet confirm or disprove their truth”
“Regularly eating (versus skipping) breakfast is protective against obesity.”
- Two randomized controlled trials (the gold standard in research design) cited in the paper found no protective benefit of breakfast on weight status, but in one study, it turned out that the benefit depended on whether or not the person was a breakfast eater or not before the study.
“Early childhood is the period in which we learn exercise and eating habits that influence our weight throughout life.”
- It is true that BMI tracks over time. It is not clear, however, whether that is due to genetic predisposition (which is fixed) or early learning (which is changeable.
“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.”
- Fruits and vegetables offer many health benefits, but contributing to weight loss without a subsequent decrease in energy intake or increase in energy expenditure is not one of them.
Weight cycling (e.g., yo-yo dieting) is associated with increased mortality.
- Observational studies in humans do in fact seem to suggest that this is true; however, the NEJM authors attribute this finding to the negative health status of those who are likely to engage in this type of dieting behavior.
“Snacking contributes to weight gain and obesity.”
- To date, studies have not confirmed this (though it seems logical that snacking would increase baseline energy intake which would subsequently lead to weight gain).
“The built environment, in terms of sidewalk and park availability, influences the incidence or prevalence of obesity.”
- It makes sense that individuals who have ready access to opportunities for physical activity will be more likely to be physically active. Thus, they will expend more energy and maintain a healthier weight. The studies to date have been observational and have led to inconsistent results.
Facts: “Propositions backed by sufficient evidence to consider them proved for practical purposes”
“…moderate environmental changes can promote as much weight loss as the most efficacious pharmaceutical agents available”
- Translated: Behavioral changes that lead to people eating less and moving more are as effective as weight-loss drugs.
“Diets very effectively reduce weight…but diet(s) generally do not work well in the long term.
- Translated: Diets don’t work. Lifestyle changes are essential for lasting weight loss.
“Regardless of body weight or weight loss, an increased level of exercise increases health.”
- Translated: Sure, exercise to lose weight, but the accompanying health benefits are reason enough to engage in a regular exercise program.
“Physical activity…aids in long-term weight maintenance”
- Translated: A compelling body of research supports that regular physical activity is a critical factor in weight-loss maintenance
“Continuation of conditions that promote weight loss promotes maintenance of lower weight.”
- Translated: The changes made to lose weight can’t stop after the weight loss is attained; rather, it needs to be a long-lasting lifestyle change.
“For overweight children, programs that involve the parents and the home setting promote greater weight loss or maintenance.”
- Translated: Any program designed to prevent or reduce childhood obesity should include the family for best results.
“Provision of meals and use of meal-replacement products promote greater weight loss.”
- Translated: To effectively lose weight, clients need help with knowing what to eat, beyond simply teaching of the principles of balance, variety and moderation.
“Some pharmaceutical agents can help patients achieve clinically meaningful weight loss and maintain the reduction as long as the agents continue to be used.”
- Translated: Weight-loss drugs can work, but the individual needs to keep using the drug for weight-loss maintenance.
“In appropriate patients, bariatric surgery results in long-term weight loss and reductions in the rate of incident diabetes and mortality.”
- Translated: Weight loss surgery is very effective for weight loss and reduction in health risk, but the patients who undergo this surgery should be carefully selected.
While this article was published by a group of scientists in a prestigious medical journal, it is worth pointing out that the authors did disclose a very long list of conflicts of interest, including widespread funding and support from weight-loss companies like Jenny Craig, food-industry giants like Kraft and Coca-Cola, a baby formula company and several pharmaceutical companies, to name a few. Clearly, these entities have a vested interest in the findings of this study and, while scientists aim to remain unbiased when conducting and evaluating research, many of the authors of this study do have a financial stake in their findings.
Now it’s time for you to weigh in. What are your thoughts about what works and what doesn’t? This discussion of myths, presumptions, and facts is based on what we know from the scientific literature, but sometimes experiences from the real world that have not yet been studied are just as meaningful and may inspire the next big research study.
Reference: Casazza, K. et al (2013). Myths, presumptions, and facts about obesity. The New England Journal of Medicine, 368, 446-454.
By Natalie Digate Muth
Natalie Digate Muth, MD, MPH, RD, FAAPNatalie Digate Muth, MD, MPH, RD, FAAP is the Healthcare Solutions Director for the American Council on Exercise, a board-certified pediatrician and Fellow of the American Academy of Pediatrics, a Diplomat of the American Board of Obesity Medicine, registered dietitian and board-certified specialist in sports dietetics, and ACE-certified health coach. She is the author of "Eat Your Vegetables" and Other Mistakes Parents Make: Redefining How to Raise Healthy Eaters" and the upcoming textbook "Sports Nutrition for Health Professionals". She has been ACE certified since 1998.