Obesity is known to increase the risk of serious health problems like type 2 diabetes and heart disease. This happens because excess weight often leads to inflammation and poor function of fat tissue.
While it’s well understood that losing weight can lower the risk of these conditions, scientists haven’t been sure if fat tissue itself can truly recover after a person loses a lot of weight. Does fat tissue hold onto a “memory” of being obese, even after weight loss?
A new study from the University of Southern Denmark offers new insights. Led by Assistant Professor Anne Loft, Associate Professor Jesper Grud Skat Madsen, and Professor Susanne Mandrup, the research shows that fat tissue can return to a healthier state after major weight loss. Their findings were recently published in the journal Nature Metabolism.
The researchers are part of the ATLAS Center of Excellence, which studies how liver and fat tissues respond to obesity and weight loss at the molecular level. This work is important because it helps explain how obesity causes diseases—and how those effects might be reversed.
In the study, researchers looked at fat tissue from people with severe obesity at three stages: first, when they were scheduled for gastric bypass surgery; second, after they lost 5–10% of their weight through diet alone just before surgery; and third, two years after surgery, when they had lost between 20% and 45% of their body weight.
Two years after surgery, the improvements in fat tissue were remarkable. The number of immune cells in the fat was much lower. In fact, several types of immune cells returned to levels usually seen in people with healthy weights.
This is important because these immune cells are linked to inflammation and reduced sensitivity to insulin in fat tissue. When fat tissue becomes resistant to insulin, it can lead to whole-body insulin resistance—a key factor in developing type 2 diabetes.
The researchers also found that blood vessel cells increased in the fat tissue. This likely helps deliver oxygen and nutrients more effectively, which is another sign of healthier tissue. Even more encouraging, gene activity in fat cells looked more like that of people who were never obese.
But what about the stage after only moderate weight loss? Doctors know that losing just 5% of body weight can improve insulin sensitivity across the whole body. Surprisingly, this study showed that at this point, inflammation in fat tissue didn’t decrease yet. That means the early improvements in insulin sensitivity must be happening for other reasons.
According to Professor Mandrup, even though inflammation didn’t go down after modest weight loss, the researchers saw changes in other important areas.
They found more of a certain type of pre-fat cell and increased activity of genes that help make new fat cells. This may mean that modest weight loss encourages the formation of newer, healthier fat cells—which could explain why the body starts using insulin more effectively.
In summary, this study shows that the harmful effects of obesity on fat tissue are not permanent. Even a small amount of weight loss begins to improve the health of fat tissue by helping the body create better-functioning fat cells.
And after major weight loss, fat tissue becomes much healthier—closely resembling that of people who have never been obese. The idea that fat tissue holds a long-term “memory” of obesity is not as true as once believed.
These findings offer real hope that the damage caused by obesity can be reversed—not just in terms of overall health, but down to the individual cells that make up our fat tissue.
If you care about weight loss, please read studies that hop extract could reduce belly fat in overweight people, and early time-restricted eating could help lose weight .
For more health information, please see recent studies that Mediterranean diet can reduce belly fat much better, and Keto diet could help control body weight and blood sugar in diabetes.
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