Expecting all obese people to lose weight solely by “eating less and moving more” misunderstands the nature of the condition and will never solve the obesity epidemic, leading doctors have said.
In a staunch rebuttal to commentators who argue obese people have brought the problem on themselves and should rely only on diet and exercise, experts from leading American universities said that, even after actively losing weight, biological mechanisms kick in that make it extremely difficult for previously obese people to stay a healthy weight.
Writing in The Lancet, they say recommendations just to cut back on high calorie foods might be “no more effective for the typical patient seeking weight reduction that would be a recommendation to avoid sharp objects for someone bleeding profusely”.
Many obese people can lose weight for a few months, but between 80 and 95 per cent regain their lost weight.
This is because cutting back on calorie intake triggers biological systems that evolved when humans needed to survive in times of scarcity.
In the modern environment, in which food is not just plentiful, but often highly calorific and aggressively advertised, these same systems, which act on the metabolism and the brain, make it hard for previously obese people to stay lean, the doctors write.
Dr Christopher Ochner, assistant professor of paediatrics and psychiatry at the Icahn School of Medicine in New York and lead author of the paper, said that in those with chronic obesity “bodyweight seems to become biologically stamped in and defended”.
“Few individuals ever truly recover from obesity; rather they suffer from ‘obesity in remission’,” he said. “They are biologically very different from individuals of the same age, sex, and bodyweight who never had obesity.”
Measures that can reverse obesity-induced changes to the body’s biology will be needed to treat many patients, according to the paper.
Weight loss surgery, which can have has this effect, has been shown to be effective in maintaining long-term weight loss. Drug treatments for obesity are not yet fully proven to work.
The Lancet paper, which is published today, coincides with the release of a new study that furthers our understanding of the genetic factors that predispose people to becoming overweight. The study, in the journal Nature, identified 97 regions in the genome that influence obesity, including genes that affect signals sent by the brain that control appetite and energy use.
Dr Rachel Batterham, head of University College London Hospital’s Centre for Weight Loss, said she saw hundreds of patients “nearly every one” of whom had successfully lost weight, only to put it back on again.
“That’s because their biology wants them to return to the maximum weight they had achieved,” she said. “Once people have become overweight, then biology changes. An understanding of how difficult it is to lose that weight and keep it off needs to be communicated.”
Professor John Wilding, of the University of Liverpool’s Institute of Ageing and Chronic Disease, who helped draw up recent NICE guidelines which will see weight loss surgery given to an estimated 15,000 people a year, said that while it was always best to begin weight loss interventions with diet and exercise, too many people, including doctors, did not understand that obese people who had lost weight would regain it if they took up their previous diet.
“It is in reality much, much harder for someone who has dropped from 15 stone down to 11 stone, to stay at 11 stone, than it is for someone who has always been at 11 stone, because they are fighting a whole set of complicated biological signals that are telling their body they should be at 15 stone,” he said.
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