Most people who are overweight want to lose it. But even when they do, it often creeps back. New research may explain why. The study focuses on the epigenome – chemical structures sitting on our DNA that regulate gene activity. Epigenetic signatures can act as a “memory” for our cells, capturing environmental stresses and changes, perhaps even from the womb. Evidence from wartime sugar rationing, for example, suggests maternal diets during pregnancy can programme a child’s propensity for weight gain later in life, likely through epigenetic changes.
Researchers wondered if an “epigenetic memory” within fat cells might also drive the body’s resistance to maintaining weight loss. To investigate, they analysed fat tissue from people with severe obesity who underwent bariatric surgery, which makes the stomach smaller. All patients lost at least 25 per cent of their body weight. Samples from before the surgery and two years after were compared to tissue from lean individuals who had never been obese.
The findings were striking: the fat cells of those who had been obese displayed different gene activity to those who had always been lean. Pathogenic signatures of obesity remained. Genes linked to inflammation and fibrosis were more active, while those associated with healthy fat tissue function were suppressed.
Similar patterns were observed in mice, reinforcing the results. In addition to epigenetic differences, fat cells from formerly obese mice continued to “act obese”: they absorbed more sugar and fat and regained weight faster on a high-fat diet than cells from lean mice. How long this “metabolic memory” persists is unknown.
This latest research contributes to an important and growing body of evidence that obesity isn’t about will power. Innovations such as Ozempic and other weight-loss drugs offer hope for severely obese individuals, but long-term success requires more than just treatment. It’s a complex challenge shaped by biology, environment and even the “memories” of our cells. With insights like these, we’re closer to removing the stigma and addressing the challenge of obesity effectively and equitably.
This article is from New Humanist’s Spring 2025 issue. Subscribe now.
