Getting on the scale is always a bit nerve-wracking. Some fluctuation is natural, but if you're constantly seeing that number go up and down—often called the "yo-yo effect"—a new study says there might be more to the story. According to findings published in Nature yesterday, the body may "remember" being overweight, keeping some stuck in this cycle.
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Researchers from ETH Zurich studied the yo-yo effect in mice, analyzing fat cells from overweight mice and those that shed weight by dieting. Interestingly, obese mice also experienced changes in their fat cells—and after they lost weight, these modifications stayed in place. When they ate a "high-fat diet" again, they regained weight more quickly than those whose cells didn't have these memories.
"The fat cells remember the overweight state and can return to this state more easily," Ferdinand von Meyenn, professor of nutrition and metabolic epigenetics at ETH Zurich, explained in a press release outlining the findings.
Fat cells' "memory" of their obese state then prepares them "to respond quicker, and maybe also in unhealthy ways, to sugars of fatty acids," von Meyenn told The Guardian.
Even further, researchers found evidence of this "molecular basis for the yo-yo effect" in humans. To do so, they analyzed fat tissue biopsies from overweight people who had stomach reduction or gastric bypass surgery and compared them with fat from people at a healthy weight who had never been obese. As The Guardiansummarizes, fat cells that had experienced obesity responded to food differently during testing, growing faster by taking in nutrients faster.
These fat cells may not be the only ones with a memory, either: Other parts of the body could contribute to the yo-yo effect, von Meyenn said. Future research is needed to examine whether cells in the brain, blood vessels, or other organs could play a role.
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But while researchers may have had a breakthrough in understanding why people's weight won't stop fluctuating, there isn't as much clarity on how long fat cells remember obesity. What they do know, however, is that fat cells don't have as quick of a turnover.
"Fat cells are long-lived cells. On average, they live for ten years before our body replaces them with new cells," study author Laura Hinte, a doctoral student at ETH Zurich, explained in the press release.
Researchers also noted that altering or erasing this memory of obesity isn't doable right now.
"Maybe that’s something we’ll be able to do in the future," Hinte said. "But for the time being, we have to live with this memory effect."
According to von Meyenn, this reinforces the need to maintain a healthy weight.
"It’s precisely because of this memory effect that it’s so important to avoid being overweight in the first place. Because that’s the simplest way to combat the yo-yo phenomenon," he said in the release.
