Cells in the body remember obesity. Here’s what that means for weight loss

These body cells remember fats. Here’s What That Means for Weight Loss

By Lori Youmshajekian edited by Lauren J. Young

Weight loss is notoriously difficult to maintain. Within a few years, most people regain the pounds they initially lost, whether through diet, exercise, surgery, or weight loss medications such as the popular glucagonlike peptide 1 (GLP-1) drugs. Recent research suggests that fat cell “memory” may explain why.

Fat-storing cells, or adipocytes, and immune cells, such as macrophages, that live in fatty tissue can remember weight long after it is lost. And scientists suggest that obesity causes lasting changes in these cells, making it easier for the body to return to an obese state, even after significant weight loss. The changes are etched into the cells’ epigenome, the instructions that tell each cell to read specific genes that control its function, says Ferdinand von Meyenn, who studies nutrition and metabolic epigenetics at the Swiss Federal Institute of Technology in Zurich. This ensures that a liver cell does not suddenly behave like a neuron, for example. In obese people, lasting epigenetic changes could cause the body to regain weight more easily if they consume more calories.

Von Meyenn’s team measured gene activity in individual cells with a technique called RNA sequencing to compare fatty tissue from obese people before undergoing bariatric surgery with similar tissue from non-obese people. Even after the obese participants lost about 25 percent of their body mass index after their surgery, some of their genes remained out of balance. This suggests that some adipose tissues did not recover from obesity: some genes controlling metabolic function and inflammation remained abnormally activated or deactivated, for example, says von Meyenn.

On supporting science journalism

If you enjoy this article, please consider supporting our award-winning journalism by subscription. By purchasing a subscription, you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Previous studies have shown that fat cells in obese mice also retain epigenetic alterations even after the animals lose weight. When then fed a high-fat diet, these mice regained weight more quickly than control animals. Laboratory tests showed that fat cells from obese mice absorbed glucose and lipids more easily. Fat cells normally absorb sugars and lipids, von Meyenn said, but these obesity-impaired cells appeared “slightly modified” to absorb more of these nutrients.

Other research groups have demonstrated that immune cells can also remember previous weight. When a person gains weight, different types of immune cells infiltrate the expanding fatty tissue, probably in response to stress, says William Scott, an obesity researcher at Imperial College London. His research showed that after bariatric surgery, the number of immune cells in people’s fatty tissues decreased significantly, but it didn’t completely reset. Immune cells retained the inflammatory characteristics that developed when people suffered from obesity.

Mouse research has echoed this finding; even after weight loss, macrophages retain epigenetic changes that keep inflammatory genes more active than usual. Another study in mice shows that weight cycling – losing and regaining weight – can intensify these changes in immune cells and worsen metabolic health more than never losing weight.

How long this epigenetic memory lasts is unclear, but fat cells can persist for up to a decade in humans, giving these cells the potential to maintain changes long-term, says von Meyenn. And fat may not be the only tissue involved. “I think changes are happening in the brain, in the liver and in the muscles,” says von Meyenn, who plans to study these areas in the future.

These results do not mean that weight loss is futile; Even short-term weight loss correlates with improved metabolic health. But the research could help explain why weight relapses are so common and why it’s important to avoid weight gain. In an environment and society that promotes weight gain, prevention is much easier said than done, says von Meyenn. Researchers, including von Meyenn, are currently studying whether fat cells can be treated to rewrite these epigenetic changes to make weight loss more sustainable and whether different types of weight loss interventions have different effects on these cells.

“There is a great desire to manufacture our weight loss drugs [such as GLP-1 medications] more powerful” to result in greater weight reductions, Scott says, “but we really need to do better at maintaining the weight loss once it happens. »

It’s time to defend science

If you enjoyed this article, I would like to ask for your support. Scientific American has been defending science and industry for 180 years, and we are currently experiencing perhaps the most critical moment in these two centuries of history.

I was a Scientific American subscriber since the age of 12, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of respect for our vast and beautiful universe. I hope this is the case for you too.

If you subscribe to Scientific Americanyou help ensure our coverage centers on meaningful research and discoveries; that we have the resources to account for decisions that threaten laboratories across the United States; and that we support budding and working scientists at a time when the value of science itself too often goes unrecognized.

In exchange, you receive essential information, captivating podcasts, brilliant infographics, newsletters not to be missed, unmissable videos, stimulating games and the best writings and reports from the scientific world. You can even offer a subscription to someone.

There has never been a more important time for us to stand up and show why science matters. I hope you will support us in this mission.