NEJM debunks seven 'myths' about obesity

Researchers also uncover 'truths' about weight loss

Does breastfeeding protect against obesity? No—although millions of Americans wrongly believe that it does. A new study in NEJM reviews the myths and truths behind weight loss.

David Allison—director of the University of Alabama's Nutrition Obesity Research Center—and his team set out to identify and debunk common obesity myths. After conducting online searches for weight loss and obesity articles in popular media, scientific literature, and public health recommendations, the team identified seven myths about obesity:

    1. Small changes in calorie intake and exercise will create big, long-term weight changes.
    2.Setting realistic goals for weight loss is important  for sustained weight loss and prevent frustration.
    3. Hefty, rapid weight loss is linked with poorer long-term outcomes than gradual weight loss.
    4. Assessing diet readiness is important for patients who seek weight-loss treatment.
    5. Physical education classes in their current form play an important role in preventing childhood obesity.
    6. Breastfeeding protects babies against obesity later.
    7. Sexual activity burns 100 to 300 calories.

Meanwhile, the team also identified six presumptions about weight loss, which were defined as unproven yet commonly espoused propositions. They included the idea that regularly eating breakfast protects against obesity and the assumption that yo-yo dieting increases mortality risks.

The researchers determined that the myths often began as one small study and then were spread by supporting association studies. "The question is: 'Is it a causal association?'" Allison says, adding that scientists "need to stop doing association studies after an association has clearly been demonstrated." Moreover, the practice can create "ineffective policy" and "unhelpful or unsafe clinical and public health recommendations," Allison says.

"Many of the myths and presumptions about obesity reflect a failure to consider the diverse aspects of energy balance, especially physiological compensation for changes in intake or expenditure," the study says.

What is true about weight loss and obesity?

In the study, the researchers identified nine truths about obesity and weight loss. They are:

    1. Genes do play a role in one's weight, but not a role that role cannot be overcome with sufficient environmental influence.
    2. Diets effectively reduce weight.
    3. Increased exercise improves health, potentially mitigating the harmful effects of obesity.
    4. Exercise in sufficient doses can help maintain weight.
    5. Maintaining conditions that first promoted weight loss helps individuals maintain lower weight.
    6. For overweight children, involving the parents is critical to reducing weight.
    7. Meal replacements and following meal plans do aid in weight loss.
    8. Some weight-loss drugs help individuals achieve meaningful weight loss.
    9. Bariatric surgery—in appropriate cases—does promote long-term weight loss and decreased risk of diabetes and mortality.

Commenting on the study, some health experts noted that the researchers involved in the study have ties to food, beverage, and weight-loss product makers, including Jenny Craig and GlaxoSmithKline.

Regardless, many health experts commended the study's efforts to dispel erroneous beliefs about weight that are making it harder to address the nation's obesity problem.

"In my view, there is more misinformation pretending to be fact in this field than any other I can think of," says Jeffrey Friedman, an obesity researcher at Rockefeller University. And "I feel like cheering" after seeing the findings, said Madelyn Fernstrom, the founder of the University of Pittsburgh Weight Management Center (Allison et al., NEJM, 1/31 [subscription required]; Petrochko, Medpage Today, 1/30; Kolata, "Well," New York Times, 1/30; Marchione, AP/Sacramento Bee, 1/30).

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