Epigenetic changes in fat cells shed light on why weight loss is hard to sustain

Even after significant weight loss, fat cells retain a ‘memory’ of obesity, according to groundbreaking research published in Nature. This discovery sheds light on why maintaining weight loss can be so challenging, underscoring the need for long-term support for individuals who achieve significant weight reductions.

The Epigenetic Memory of Obesity

The study reveals that obesity triggers changes in the epigenome—chemical modifications to DNA and proteins that regulate gene activity. These epigenetic alterations disrupt the normal functioning of fat cells, impairing their ability to operate as they would in a body without obesity. Crucially, these changes persist even after weight loss brings body weight to a healthy level.

This persistence highlights the complexity of obesity as a condition, suggesting that maintaining weight loss often requires more than personal effort. Co-author Laura Hinte, a biologist at ETH Zurich, explained that the findings emphasise the need for additional support. “It means that you need more help, potentially,” she said, adding that this reinforces the idea that “it’s not your fault.” By uncovering the molecular underpinnings of this phenomenon, the study offers an explanation for the enduring challenges many individuals face after weight loss.

Exploring the Molecular Mechanisms

To investigate why weight is often regained after loss, researchers examined fat tissue from individuals with severe obesity and compared it to fat tissue from people who had never experienced obesity. They discovered significant differences in gene activity: some genes were more active in the fat cells of individuals with obesity, while others were less active.

Even after weight-loss surgery, the genetic activity in fat cells from participants with a history of obesity remained altered. Two years post-surgery, despite substantial weight reductions, the fat cells still displayed an obesity-linked pattern. Similar results were observed in mice, further supporting the findings.

The Lasting Impact of Obesity on Fat Cells

The research pinpointed specific genes that were affected by obesity. Genes that promote inflammation and fibrosis (the formation of stiff, scar-like tissue) were dialled up, while those essential for normal fat cell function were suppressed. These changes were traced to alterations in the epigenome, which dictate whether specific genes are switched on or off.

The durability of this ‘memory’ was tested by placing mice with obesity on a diet. Despite becoming lean again, their fat cells continued to exhibit obesity-related epigenetic changes months later. Co-author Ferdinand von Meyenn, an epigenome specialist at ETH Zurich, noted that while it is unclear how long the body retains this memory, “there may be a time window when this memory will be lost,” although “we don’t know” for certain. This lingering effect demonstrates how deeply obesity can alter the body at the cellular level.

Effects of Fat Cell Memory on Metabolism

The persistent memory of obesity has profound implications for metabolism. Fat cells from mice formerly with obesity absorbed more sugar and fat than those from control mice that had never had obesity. Moreover, when placed on a high-fat diet, the mice formerly with obesity regained weight more quickly than their counterparts who had never had obesity.

While these findings are striking, the study stops short of proving a direct causal link between epigenetic changes and altered fat cell function. Scientists such as Evan Rosen, a biologist at Beth Israel Deaconess Medical Center in Boston, pointed out that although the research provides a valuable list of epigenetic alterations, determining which changes drive the fat cells’ lingering memory will be challenging. Von Meyenn acknowledged this limitation, stating that “it’s not yet a causal link,” but rather “correlation” that his team continues to explore.

Implications for Weight Loss and Obesity Stigma

The study’s findings have broader implications for addressing obesity-related stigma. They suggest that the biological changes caused by obesity create long-term challenges that cannot simply be overcome with willpower alone. Von Meyenn stressed the importance of preventing obesity in the first place, explaining that while people who lose weight can remain lean, “it will require a lot of effort and energy to do that.”

By uncovering the epigenetic mechanisms that underlie obesity and its lingering effects, the research may pave the way for improved treatments and support systems. This, in turn, could help reduce stigma and foster greater understanding of the biological challenges faced by individuals seeking to manage their weight long-term.