These cells of the body remember fat. Here’s what it means for weight loss
Obesity leaves a lasting imprint on fat and immune cells in such a way that it may be difficult to avoid regaining weight.
Colored scanning electron micrograph (SEM) of a sample of adipose tissue, showing fat cells (adipocytes).
STEVE GSCHMEISSNER/Science Photo Library/Getty Images
Maintaining weight loss is extremely difficult. Within a few years most people regain the pounds they lose, whether through dieting, exercise, surgery, or weight loss medications such as the popular glucagonlike peptide 1 (GLP-1) drugs. Recent research suggests that the “memory” of fat cells may explain the reason.
Cells that secrete fat, or adipocytes, and immune cells, such as macrophages, that reside in adipose tissue can remember weight gain long after it has been lost. And scientists suggest that obesity causes permanent changes in cells that make it easier for the body to revert to obesity even after significant weight loss. changes marked in the epigenome of cellsThe instructions that tell each cell to read the specific genes that control their function, explains Ferdinand von Meyen, who studies nutritional and metabolic epigenetics at the Swiss Federal Institute of Technology Zurich. This ensures that, for example, a liver cell does not suddenly behave like a neuron. In obese people, permanent epigenetic changes may lead the body to gain weight back more easily if they consume more calories.
Von Meyn’s team measured gene activity in individual cells with a technique called RNA sequencing, to compare the fat tissue of people with obesity, before they had bariatric surgery, with similar tissue from people who did not have obesity. Even obese participants lost about 25 percent of their body mass index after surgery, despite this. some of their genes remained defective. This suggests that some fat tissue has not recovered from obesity – for example, some genes that regulate metabolic function and inflammation are abnormally turned on or off, explains von Meyen.
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Previous studies have shown that obese mice also have fat cells maintain epigenetic changes Even after the animals become thin. When they were later fed a high-fat diet, these mice regained their weight faster than control animals. Lab tests showed that the fat cells of obese mice absorbed glucose and lipids more easily. Fat cells normally take up sugars and lipids, but these cells, altered by obesity, appear to be “slightly modified” to absorb more of those nutrients, says von Mayen.
Other research groups have demonstrated that immune cells can also remember former weight. William Scott, an obesity researcher at Imperial College London, explains that when a person gains weight, different types of immune cells infiltrate the fat tissue, causing it to expand as a stress response. Their research showed that, after bariatric surgery, the number of immune cells in people’s fat tissues decreased dramatically, but not everything was completely reset. immune cells retained inflammatory characteristics It developed when people became obese.
Research on rats has replicated this finding; Even after weight loss, macrophages retain epigenetic changes that keep inflammatory genes more active than normal. Another mouse study suggests that weight cycles – losing and regaining weight – may accelerate these immune cell changes. poor metabolic health More than never losing weight.
How long this epigenetic memory lasts is not clear, but fat cells can lasts for a decade In humans, those cells gain the ability to maintain changes over longer periods of time, says von Mayen. And fat may not be the only tissue involved. “I believe there are changes happening in the brain, in the liver, in the muscles,” says von Meyen, who plans to investigate these areas further.
These findings do not mean that weight loss is futile; Even short-term weight loss is associated with improvements in metabolic health. But research may help explain why weight regain is so common and why avoiding weight gain matters. Von Mayen says that in an environment and society where weight gain is common, prevention is easier said than done. Researchers including von Meyen are now exploring 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’s a big push to make our weight loss drugs (like GLP-1 drugs) more powerful” to achieve weight loss, Scott says, “but once the weight is lost, we really need to do better at maintaining it.”
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