Fat has a “memory” that could explain the rebound effect in diets

they call it rebound effect or yo-yo effect. This is what happens when a person (you, for example) gets lose weight with a diet but it tends to recover at the end of the “shock therapy.” This is a difficulty in maintaining the achieved result that many formerly obese or overweight people experience. Adding to the problem is the fact that no complete explanation has been found. Although there is something that much of the scientific community is now convinced of: it is not always just a matter of willpower and choices.

Now, a new study, which has just be published in the magazine Natureadds a new piece to the understanding of the phenomenon: the genetic expression of adipose cells of the people obese remains different from that of the adipose cells of people of average weight, even long after losing weight. A kind of fat ‘memory’which behaves as if the body were still obese.

The “memory” of fat

It is no mystery that, at the end of the hardest phase of a weight loss program, it is usually very difficult to maintain the achieved result. And this is the case even if the advice of experts is followed and the course is not deviated. The reason, however, still not entirely clear.

To find out if there are molecular reasons for the rebound effect, a team from ETH Zurich analyzed fat cells from obese and normal-weight people and discovered that populations of RNA (that is, molecules that indicate the expression of a certain gene) are different: some genes are more active and others less. And not only that. These differences they remain even two years after drastic weight loss (at least 25% of the initial mass), after bariatric surgery, of obese people. In other words, It seems that adipose cells retain a kind of memory of the previous condition of obesity. Similar results were also obtained in cells from mice subjected to comparable conditions.

Gene activity and cellular behavior

By looking at animal cells, scientists realized that the difference in gene activity is due to epigenetic changesthat is, chemical changes in DNA or associated proteins that influence gene expression. Some changes make genes more accessible and therefore more active, while others prevent genes from being read and expressing their function.

Specifically, in the fat cells obese or reminiscent, the genes involved in inflammatory and fibrotic processes (when scar tissue forms) are more active, while the genes that help fat cells function normally are turned off. What the researchers discovered was that the fat cells that they had been obese They tended to absorb more sugar and fat than those of control mice that had never been obese. Additionally, when placed on a high-fat diet, previously obese mice were more likely to gain weight more quickly than controls.

Cause-effect?

The study opens new perspectives on cellular metabolism in normal and pathological conditions, but, as the authors of the research themselves admit, several pieces are still missing. The work, in fact, testifies to an association between a certain gene expression profile/epigenetic alterations and the rebound effect after weight loss, but does not demonstrate a causal effect. Furthermore, it has not yet been possible to establish How long does the molecular memory of adipose cells, if it exists. In any case, these findings contribute to dismantling the stigma that still surrounds obesity.

Article originally published in WIRED Italy. Adapted by Mauricio Serfatty Godoy.