Top Seven Obesity Myths

We “just know” that having sex burns enough calories to make a difference, breastfeeding protects a baby against future obesity and gym classes keep kids thin.

It turns out these are among many popular obesity myths; widespread beliefs held dearly despite evidence to the contrary. That is the conclusion of an article just published in the New England Journal of Medicine. Such inaccurate beliefs, the authors argue, are leading to inaccurate public health recommendations, wasted resources and a less healthy America.

David Allison, Ph.D., associate dean for science in the UAB School of Public Health, led a research team that analyzed articles published in the scientific and popular press to separate myths from evidence-supported facts.

The authors also defined six “presumptions” – beliefs held to be true even though more studies are needed. For instance, some have presented as fact the idea that regularly eating versus skipping breakfast contributes to weight loss, but the few studies that have been done have found no effect.

The team identified research-proven facts as well. Weight-loss programs for overweight children that involve parents and the child’s home, for instance, achieve better results than programs that take place in schools. Also, many studies show that while genetic factors play a large role in obesity, “heritability is not destiny.” Big enough changes to lifestyle and environment can bring about as much weight loss as the most effective weight-loss drugs. This is the kind of information that should be shaping public policy, Allison said. The most valuable message is an old, unpopular one: eat less in general and use up more energy than you take in.

For more on the top myths, presumptions and facts, please see the UAB press release and the NEJM article it covers.

Dr. Allison added that the field should conduct more randomized, controlled clinical trials to answer key obesity questions as it advises the public. This type of study rules out chance effects and counters researcher bias. Public health advocates, says Allison, need to be clear with the public about what has and has not been proven. Mixing seemingly good ideas in with proven ideas does not serve the public good.

Allison said the widespread acceptance of obesity myths and presumptions raises the larger question of why we so often believe things that are not so. The authors identified several factors that seem to contribute to this. One is the “mere exposure effect,” where repeating an idea often enough makes people more likely to believe it. Another factor is that people may like certain ideas so much that they hesitate to let them go despite evidence to the contrary. Then there is the phenomenon of “confirmation bias,” where we tend to systematically seek out only the sources of information that confirm our opinions.

Given this whirlwind of effects, it is a wonder we know anything at all.

Do sugar-sweetened drinks drive obesity?

Obesity has been linked in media coverage to the drinking of too many sugar-sweetened beverages. Emotions are running high, but is there enough scientific evidence to conclude that consuming fewer sugary drinks will reduce obesity?

The Obesity Society opened its annual meeting, Obesity 2012, this week in San Antonio with a debate on that very subject.

In the debate, David Allison, Ph.D., associate dean for science within the UAB School of Public Health and director of the NIH-funded UAB Nutrition Obesity Research Center, faced off against Frank Hu, M.D., Ph.D., professor of Nutrition and Epidemiology at Harvard School of Public Health.

Allison sat down with The Mix to comment on the debate and on related studies just published in the New England Journal of Medicine.

Show notes on the interview

1:25 Sugar-sweetened beverages have figured centrally in public health discussions about obesity for more than a decade. Some evidence has suggested that such drinks may play a unique role. What’s needed now, says Allison, are rigorous studies to prove (or disprove) that reducing consumption of these beverages actually increases weight loss or slows weight gain.

2:02 Public health as a field changed over the last decade as the obesity epidemic became more evident. Advocacy has wrestled with purely scientific discussion, and emotions are running high.

3:44 Valid, scientific study results are a must when deciding whether or not any one factor contributes to, or reduces, obesity, and the standard for that validity is a randomized clinical trial.

4:38 Up until the meeting, the evidence has not been there to demonstrate that reducing sugar-sweetened beverage intake would reduce obesity, according to Allison. In six of the six randomized clinical trials to date, he argues, the primary analysis of all patients studied showed no statistically significant difference in weight gain, weight loss or BMI between those who kept drinking sugary drinks and those who cut back.

5:26 On top of the six clinical trials mentioned, however, a series of papers were just this minute published in the New England Journal of Medicine. Two of the studies — one in children, one in adolescents — did indeed represent the kind of randomized clinical trials Allison has been calling for. The authors of both studies offer valid evidence, Allison says, that reducing consumption of sugar-sweetened beverages reduced weight gain in specific groups under certain conditions, but more studies are needed to confirm that the patterns apply to everyone.

9:23 While sugar-sweetened beverages remain an important area of inquiry, Allison says he thinks other emerging thrusts in obesity research warrant attention as well. These include the roles of sleep, daily weigh-ins and eating vs. skipping breakfast.

10:32 UAB’s Nutrition Obesity Research Center has joined with six other NORCS and a center in Denmark to organize a randomized clinical trial in 300 patients to generate evidence that having or skipping breakfast in the morning affects body weight.

11:36 UAB meeting highlights beyond the presidential debate included a presentation by Nefertiti Durant, M.D., assistant professor in the UAB School of Medicine's Division of General Pediatrics and Adolescent Medicine, as part of a symposium on adjusting obesity prevention approaches to account for a person’s age. Her talk, titled “Freshman 15 and Beyond,” discussed contributing factors and potential solutions. In addition, James Rimmer, Ph.D., Lakeshore Foundation Endowed Chair in Health Promotion and Rehabilitation Sciences in the UAB School of Health Professions, will be talking about how people with intellectual disabilities have higher rates of obesity than the general public based on several factors, including their living arrangements.

13:10 For good information on obesity, Allison recommends the Weight-control Information Network organized by the National Institute of Diabetes and Digestive and Kidney Diseases. He also points to the U.S. Agriculture Department’s Dietary Health page. For researchers, Allison offers the UAB NORC’s seminar series, which is available to all online, goes back 12 years and discusses a great many aspects of nutrition theory and related scientific evidence.

Also important is a recent editorial in the Journal of the American Medical Association by the director of the National Institutes of Health, Francis Collins, M.D., Ph.D. Of the editorial, which argues that public policy must be founded on valid science, Dr. Allison says he couldn’t agree more.

14:22 End podcast

About the podcaster

Greg Williams @gregscience @themixuab is research editor within Media Relations at the University of Alabama at Birmingham.