Sometimes, good memory can be bad news.
It turns out fat cells have excellent memory. Researchers published a study in Nature that explains how that memory works and why it is so persistent. The work describes the genetic and cellular mechanisms that make the "Yo-Yo effect," a common phenomenon where a person can lose weight, but it returns right away.
The Persistence of Fat Cells
This result has especially profound implications in the U.S. where about 40 percent of adults are either overweight or obese. It may explain why diet and exercise alone often can’t help people maintain their weight loss. And it may indirectly be an argument in favor of drugs like Ozempic.
The core of why fat cells are so stubborn comes down to epigenetics — a relatively new area of study that shows how long-ago events, experiences, or environmental exposures can affect a person’s genetic information. For example, research has shown that someone who survived trauma as a child — say abuse or neglect — will suffer long-lasting changes to their DNA, which, in turn can affect cells, potentially manifesting as diseases or chronic conditions. These genetic changes can even be passed on through the generations.
Researchers at ETH Zurich discovered that this same mechanism affects fat cells. They first looked at mice — analyzing targeted parts of the genome in lean, obese, and formerly obese mice. They also studied genes in mice fat cells.
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Molecular Basis for 'Yo-Yo Diet'
They found that mice who slimmed down from their obese states retained epigenetic markers associated with their heavier conditions.
“The fat cells remember the overweight state and can return to this state more easily," said Ferdinand von Meyenn, an ETHZ professor and author of the study, in a press release. “That means we’ve found a molecular basis for the yo-yo effect.”
The scientists then turned to humans. The ETH Zurich researchers looked at fat tissues taken from overweight patients following weight reduction surgeries. Although the scientists studied gene expression in those samples rather than epigenetic markers, the results were consistent with the post-weight loss mice.
These results emphasize the importance of preventing weight gain, since fat cells — and the memories they hold — can live up to 10 years. Something the researchers haven’t investigated is how long fat cells can remember obesity.
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Prevention Is Paramount
“It’s precisely because of this memory effect that it’s so important to avoid being overweight in the first place,” Von Meyenn said in the statement. “Because that’s the simplest way to combat the yo-yo phenomenon.”
In the future, researchers may identify a way to target epigenetic markers to make weight loss both easier and more sustainable. But that will be a long way off, because scientists have yet to find a way to target those markets, much less develop, then test, medicines that will impact them. Researchers will also examine cells in the blood, brain, and other places to see if they, too, contribute to the fat memory effect.
While the study doesn’t provide an easy roadmap to lose weight and maintain a healthy weight, it at least provides some scientific consolation for folks struggling with this common experience.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature. Adipose tissue retains an epigenetic memory of obesity after weight loss
National Institute of Diabetes and Digestive and Kidney Diseases. Overweight & Obesity Statistics
Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
