After dieting, it is difficult to maintain weight, because fat cells have an epigenetic “memory” that easily causes them to revert to their previous overweight state.
- The yo-yo effect after dieting is linked to obesity memory.
- The latter arises because the experience of obesity leads to changes in the epigenome (chemical markers that can be added to or removed from the DNA and proteins of cells and which help to increase or decrease the activity of Genoa).
- This alteration, along with changes in gene activity, can persist long after weight has returned to healthy levels.
Obesity and associated comorbidities pose considerable health risks. One of the main clinical goals in the management of this metabolic disease is to lose weight sustainably, through dietary and lifestyle interventions, pharmaceutical treatments or bariatric surgery. Strategies based on behavioral and dietary changes often only achieve short-term weight loss and are prone to the “yo-yo” effect, which results in weight regain over time. According to researchers at the Swiss Federal Institute of Technology in Zurich (Switzerland), this recurring pattern can be partially attributed to epigenetic (obesogenic) memory that persists even after notable weight loss or metabolic improvements.
Genes more active in fat cells of obese patients before and after bariatric surgery
To reach this conclusion, scientists carried out a study published in the journal Nature. As part of the work, they wanted to learn more about the yoyo effect. So, the team examined adipose tissue from mice, a group of adults suffering from severe obesity, as well as a control group of healthy people. She found that some genes were more active in the fat cells of the obese group than in those of the control group, while other genes were less active. Another finding: Two years after the obese participants underwent bariatric surgery, they had lost a lot of weight, but the genetic activity of their fat cells still showed the pattern linked to obesity. In fat cells, genes activated during obesity are involved in stimulating inflammation and fibrosis, the formation of stiff, scar-like tissue. Disabled genes help fat cells function normally.
Yoyo effect: mice carrying obesogenic memory show rapid weight regain
Next, the researchers wanted to assess the durability of these changes by putting obese mice on a diet. A few months after the animals became thin again, the changes in their epigenomes (which have a powerful effect on a gene’s activity) persisted, as if the cells “remembered” being in an obese body. In detail, their cells absorbed more sugar and fat than the fat cells of rodents that had never been obese. Previously obese mice also gained weight more quickly on a high-fat diet than control mice.
“It is not known exactly how long the body remembers obesity. There may be a window of time during which this memory will be lost. But we do not know,” explained Ferdinand von Meyennepigenome specialist at ETH Zurich and co-author of the research. He added that, for the time being, “there is not yet a cause and effect link” between epigenetic alterations in adipose cells and persistent cellular memory. “It’s a correlation. We’re working on it.” However“the results suggest that people trying to lose weight will often need long-term care to avoid regaining weight,” concluded Laura Hinte, who participated in the study.
In France, as in most countries in the world, overweight and obesity continue to increase. Currently, nearly one in two adults is affected, or 48.8% of the French population, according to an epidemiological study national campaign on weight and obesity of the National League Against Obesity, in 2024.
