Researchers at the University of Alabama at Birmingham say it is time to abandon some popular but erroneous obesity myths. In an article published June 23 in Critical Reviews in Food Science and Nutrition, the research team presents nine obesity myths and 10 commonly held but unproven presumptions that the authors suggest lead to poor policy decisions, inaccurate public health recommendations and wasted resources.
The work is an expansion of a study first published in the New England Journal of Medicine on Jan. 31, 2013.
"Obesity is a topic on which many views are strongly held in the absence of scientific evidence to support those views, and some views are strongly held despite evidence to contradict those views," said David Allison, Ph.D., associate dean for science in the UAB School of Public Health and senior author of the paper. "We refer to the former as presumptions and the latter as myths."
For each of the 19 myths or presumptions, Allison's team -- made up of international experts in obesity and nutrition -- describe the belief and offer evidence on why the belief is widely held. They then present the arguments used to either support or refute the belief. They also present evidence from randomized controlled trials when available.
For each of the nine myths, the author's conclusions and recommendations to policymakers and the public are the same. Abandon, and move on.
"It's vitally important to label these myths for what they are to prevent a misallocation of the resources available to address obesity, which is a serious public health problem," said Krista Casazza, Ph.D., assistant professor in the UAB Department of Nutrition Sciences and first author of the paper. "One intent with this paper is to offer conjecture on why these beliefs may be so widely held so we can find ways to limit the spread and dissemination of unsubstantiated beliefs going forward."
The nine obesity myths are:
• Losing weight quickly will predispose to greater weight regain relative to losing weight more slowly.
• Setting realistic weight loss goals in obesity treatment is important because otherwise patients will become frustrated and lose less weight.
• Assessing "stage of change" or "readiness" to diet is important in helping patients who pursue weight loss treatment to lose weight.
• Physical education classes, as currently delivered, play an important role in reducing the prevalence of childhood obesity.
• Breastfeeding is protective against obesity in breastfed offspring.
• Daily self-weighing interferes with weight loss.
• Genes have not contributed to the obesity epidemic.
• The freshman year of college is associated with or causes 15 pounds of weight gain.
• Food deserts (i.e., areas with little or no access to stores offering fresh and affordable healthy foods, including produce) lead to higher obesity prevalence.
The 10 presumptions are defined as beliefs that do not have definitive studies to support them. Casazza and Allison suggest those studies need to be done.
"These presumptions are often the force that drives decisions about obesity treatment, public health policies, public health recommendations or future research," said Casazza. "We need to generate the evidence in those areas where evidence is lacking. For many of the beliefs presented, randomized controlled trials would not be unduly difficult or expensive, and yet they have not been done."
The presumptions are:
• Regularly eating (versus skipping) breakfast is protective against obesity.
• Eating close to bedtime contributes to weight gain.
• Eating more fruits and vegetables will lead to weight loss or less weight gain, regardless of whether one intentionally makes any other changes to one's behavior or environment.
• Weight cycling (i.e., yo-yo dieting) increases mortality rate.
• Snacking contributes to weight gain and obesity.
• The built environment, in terms of sidewalks and park availability, influences obesity.
• Reducing screen time will decrease obesity in children.
• Decreasing the portion sizes served leads to less food intake without people being told to reduce their food intake or presumably intending to do so, even when the total food available is not limited.
• Participation in family mealtimes reduces obesity.
• Drinking more water will reduce energy intake and will lead to weight loss or less weight gain, regardless of whether one intentionally makes any other changes to one's behavior or environment.
Allison says 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 phenomenon. One is what psychologists call the "mere exposure effect" -- 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 sources of information that confirm our opinions. "Fortunately, the scientific method and logical thinking are there to detect erroneous statements, counter bias and increase knowledge," said Allison. "We believe scientists need to seek answers to questions using the strongest experimental designs. As a scientific community, we need to be honest with the public about what we know and don't know as we evaluate proposed strategies for weight loss or obesity prevention."
The authors also offer another suggestion that they believe would contribute to a more rational dialogue on obesity.
"In recent years, with the rise of the obesity epidemic, numerous papers have used the rhetoric of war in describing our efforts to abate this epidemic," said Casazza. "Indeed, it is well-documented that, under conditions of war or extreme emotional situations, propaganda is used and complex messages are distorted into simplistic slogans regardless of their truthfulness. As scientists, we should resist this sloganeering and perhaps downplay the emotional rhetoric of war, which may lead to a willingness to distort information and gloss over complexities."
- Krista Casazza, Andrew Brown, Arne Astrup, Fredrik Bertz, Charles Baum, Michelle Bohan Brown, John Dawson, Nefertiti Durant, Gareth Dutton, David A. Fields, Kevin R. Fontaine, David Levitsky, Tapan Mehta, Nir Menachemi, Pk Newby, Russell Pate, Hollie Raynor, Barbara J. Rolls, Bisakha Sen, Daniel L. Smith, Diana Thomas, Brian Wansink, David B. Allison, A. Bray George. Weighing the Evidence of Common Beliefs in Obesity Research. Critical Reviews in Food Science and Nutrition, 2014; 00 DOI: 10.1080/10408398.2014.922044
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