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.
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.