Society's bias against overweight people has led health researchers to focus almost exclusively on dieting as a way to improve health, despite a lack of evidence it is effective.
The claim comes from Lucy Aphramor, a dietitian and senior research assistant in the Applied Research Centre in Health and Lifestyle Interventions at Coventry University.
In a paper published in July in the Nutrition Journal, she wrote that existing research on weight management "fails to meet the standards of evidence-based medicine", does not adequately discuss "controversies and complexities in the evidence base", and is "characterised by speculative claims that fail to accurately represent the available data".
She told Times Higher Education she did not believe researchers were deliberately pursuing an ideological agenda, but said they were unconsciously influenced by society's "moral agenda" against overweight people.
"The convention is taken to be value-free and any challenge to it is seen to be ideological and isn't seriously engaged with," she said. "There is an assumption that if most people believe something, it must be true. It isn't a deliberate conspiracy but the evidence gets continually misrepresented."
Ms Aphramor advocates an approach she calls "Health at every size" (HAES), which emphasises the health benefits of factors such as a healthy diet and exercise regardless of people's size. She admitted this approach was also "ideological" but claimed it was more evidence-based.
Ms Aphramor's paper, "Validity of claims made in weight management research: a narrative review of dietetic articles", is based on a survey of papers about weight loss published in the Journal of Human Nutrition and Dietetics between 2004 and 2008. It concludes that all of the articles "unfailingly frame fatness as a pathological condition that is primarily under personal control through volitional modification of eating and exercise habits".
But Ms Aphramor said such claims "misrepresent" the evidence. Dieting was rarely a successful long-term way to lose weight, and studies had neglected the negative psychological effect of unsuccessful dieting, such as low self-esteem. "At worst, dieting is seen as a benign experiment," she argued. The "bad science" around dieting also reinforced social prejudice against overweight people. "It becomes OK to insult them," she said.
Ms Aphramor said policymakers had criticised her attempts to promote HAES because it discredited Department of Health policy and could make dietitians' jobs more difficult. "I've also been told I am doing harm of a similar ilk to that of the pro-smoking lobby," she added.