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Researchers aim to debunk common obesity myths

By Caroline Scott-Thomas, 05-Feb-2013

Related topics: Science & Nutrition

Most people trying to lose weight will have heard that they should aim for a gradual loss in order to avoid regaining weight, and that they should not skip breakfast – but these commonly held beliefs have not been proven, according to a new paper in the New England Journal of Medicine.

The study’s senior author, David Allison, directs the National Obesity Research Center at the University of Alabama at Birmingham, and he says some myths and presumptions about the causes of obesity and best weight loss strategies prevail even among many academics and public health experts.

“Passionate interests, the human tendency to seek explanations for observed phenomena, and everyday experience appear to contribute to strong convictions about obesity, despite the absence of supporting data,” the paper said.

It aims to debunk seven common obesity myths, defined as beliefs for which there is strong refuting evidence, as well as six presumptions about obesity, for which there is no strong evidence to confirm or disprove them.

Incremental loss?

The myths include the idea that small, sustained changes, like walking for ten minutes a day or eating two more potato crisps, will have a cumulative effect on weight over time. However, recent studies have shown that this theory does not take into account variation in the person’s body composition in response to such changes. They may have an effect, but not as large an effect as is often supposed.

Other myths include the importance of being ‘ready’ to lose weight, setting realistic weight loss goals in order to avoid becoming discouraged, and losing weight gradually – or risk putting the weight back on. All of these ideas have been disproved, Allison et al. wrote.

Physical education

Physical education is also often advocated as a means to prevent childhood obesity, despite no evidence supporting this assumption. The researchers note that there is evidence that physical activity in sufficient quantity can be useful for weight maintenance, but mere participation in physical education programmes has not been shown to be effective.

Among the presumptions people make about obesity and weight loss, the authors point to the idea that snacking necessarily leads to weight gain, increasing fruit and vegetable consumption will lead to weight loss, and regularly eating breakfast is protective against weight gain. None of these presumptions has been scientifically proven, they said.

“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,” they wrote.

“…Interested parties do not regularly request the results from randomized, long-term studies that measure weight or adiposity as an outcome. Therefore, the presented data are rife with circumstantial evidence, and people are not informed that the existing evidence is not compelling (e.g., breakfast consumption). Furthermore, some suggested treatment or prevention strategies may work well (e.g., increasing the consumption of fruits and vegetables) but only as part of a multifaceted program for weight reduction. Yet such a strategy is often presented as though it will have effects in isolation and even among persons not participating in weight-loss programs. We must recognize that evidence that a technique is beneficial for the treatment of obesity is not necessarily evidence that it will be helpful in population-based approaches to the prevention of obesity, and vice versa.”

 

Source: New England Journal of Medicine

2013; 368:446-454 DOI: 10.1056/NEJMsa1208051

“Myths, Presumptions, and Facts about Obesity”

Authors: Krista Casazza, Kevin R. Fontaine, Arne Astrup, Leann L. Birch, Andrew W. Brown, Michelle M. Bohan Brown, Nefertiti Durant, Gareth Dutton, Michael Foster, Steven B. Heymsfield, Kerry McIver, Tapan Mehta, Nir Menachemi, P.K. Newby, Russell Pate, Barbara J. Rolls, Bisakha Sen, Daniel L. Smith, Diana M. Thomas, and David B. Allison