Fat cells can retain a memory of past obesity, a study suggests, which may prepare the cells to grow when exposed to high-fat foods.
Published in Nature, a new study suggests fat cells may keep a memory of previous weight gain. Without weight-loss medications or bariatric surgery, most people will return to their original body mass within a few years of losing weight through a diet. As a result, this can lead to ‘yo-yo dieting’.
Scientists don’t know why this happens, but suggest that genetics, environment and health history likely all play a role.
But according to Dr Katherine Saunders, an obesity physician at Weill Cornell Medicine, this new research ‘might add to the growing body of evidence that disproves lack of willpower as the underlying force behind “weight cycling”.’
In the new study, scientists observed mice that were given a high-fat diet before switching back to a normal diet to return them to their starting weight. Once they dropped the extra weight, the mice were metabolically indistinguishable from mice that were never fed a fatty diet.
However, when the researchers looked at the mice’s fat cells, they found that despite their weight loss, the cells still carried epigenetic changes that had taken place during the weight gain.
To check whether this also happens in humans, the team then analysed cells from people who had undergone bariatric surgery. Study co-author Laura Hinte said the team found patterns of gene activity that suggested epigenetic changes took place and continued after weight loss.
Complexity of human obesity
Hinte said: ‘From an evolutionary perspective, this makes sense. Humans and other animals have adapted to defend their body weight rather than lose it, as food scarcity was historically a common challenge.’
Dr Fatima Cody Stanford is an associate professor of medicine and paediatrics at Harvard Medical School. Not involved in the study, she said it ‘offers valuable insights into why maintaining weight loss is challenging’.
However, she warned that the observations in mice ‘may not fully represent the complexity of human obesity’.
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