Losing weight is hard—but keeping it off may be even harder. Now, researchers say that fat cells might be to blame, due to a phenomenon known as “metabolic memory.”
A study published in Nature suggests fat cells retain a memory of obesity, influencing the body’s metabolism even after weight loss. Swiss scientists found that fat cells in formerly obese mice continued to display abnormal behaviors, including inflammation, poor sugar regulation, and altered fat storage—even after the mice returned to a normal diet and lost weight.
These mice also regained weight faster than lean counterparts when reintroduced to a high-fat diet, indicating long-term metabolic changes. The same trend appeared in humans. In participants who underwent bariatric surgery, fat cells still showed abnormal gene activity and signs of inflammation two years after weight loss—unlike those in people who were never obese.
“This research suggests fat cells don’t fully return to normal after weight loss,” said Gretchen Zimmermann, a registered dietitian not involved in the study. However, she added, weight regain isn’t solely about biology. Genetics, environment, mental health, and lifestyle all play a role.
Experts recommend regular exercise, building muscle, and eating a diet rich in protein, fiber, and plant nutrients to reduce inflammation and support long-term metabolic health—even if weight loss is slow or plateaus.
Obesity, experts say, is a chronic condition often influenced by epigenetics—how lifestyle and environment affect gene expression. That may explain why some people are more prone to regain weight than others, despite healthy efforts.
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