Research indicates that a fat cell's "memory" of past obesity influences how it reacts to food, which may be the reason why maintaining weight loss is such a challenge.
Following a period of several months of a healthy diet and regular exercise.
Research published in the Nature journal discovered that fat cells possess a biological "memory" of past obesity and actively strive to revert back to this state.
The research discovered that it's not the quantity of fat cells that changes when a person gains weight, but rather how the existing fat cells store nutrients.
This "obesity memory" can persist for years after a person has lost weight, making them more susceptible to regaining weight.
"Our research shows that one of the main reasons maintaining weight loss is so challenging is because the body's natural memory of its original weight makes it hard to stick to a lower weight," said Ferdinand von Meyenn, co-author of the study and director of the Institute of Food, Nutrition and Health at ETH Zurich in Switzerland.
The yo-yo effect of weight gain due to fat cells.
The researchers found these "fat cell memories" by studying fat tissue from individuals who underwent weight loss surgery, comparing it to similar tissue from people who had never experienced obesity.
Some genes were more active in the fat cells of those who were obese compared to the control group. These genetic differences persisted even after the individuals had undergone weight-reduction surgery.
This led researchers to discover that the molecular memory in fat cells was caused by epigenetic modifications to the genome.
Epigenetic changes occur when gene expression is influenced by our surroundings - implying that rapid weight gain is not solely inherited, but can also be a result of life's experiences.
Cells with a memory capacity for storing nutrients store them in a distinct manner.
Further investigation by the team revealed that fat cells from obese mice reacted to food in a different manner than cells from non-obese mice.
"Obese mice tend to regain weight more quickly when fed a high-calorie diet, and we've found similar indirect evidence in humans," said Laura Hinte, a nutrition and metabolic epigenetics expert at ETH Zurich.
It appears that the memory of obesity led to these fat cells becoming more receptive to expanding and absorbing more nutrients more quickly.
Penny Ward, a physician-doctor at King's College London, UK, commented: "This explains why many people notice that it takes a shorter time to regain weight after they stop dieting than it did for them to initially gain weight."
The researchers in Zurich conducted an experiment with mice on a weight-reduction diet. They discovered that the mice retained the memory of obesity and regained weight at a faster rate compared to the control group.
"The environment, which could be connected to regaining body weight after a diet," von Meyenn explained in an email to .
Fighting against the natural inclination towards weight gain.
The authors stated that it is probable that other factors, located elsewhere in the body, also play a role in the phenomenon of weight loss followed by weight gain.
An "obesity" memory in fat cells alone does not account for the rapid weight gain, said von Meyenn. "If similar mechanisms are present in brain cells, which regulate food consumption, for instance, this could help explain the yo-yo effect seen in weight regain."
This makes sense from an evolutionary standpoint, von Meyenn said. Humans and other animals have adapted to preserve their body weight rather than lose it, as food scarcity has been a frequent and recurring challenge throughout history.
"This could provide some comfort to individuals struggling with obesity on a societal level, as it implies that the challenge in maintaining weight loss may not be solely due to a lack of willpower or motivation, but rather to a deeper cellular memory that actively resists change," said von Meyenn.
How long do fat cell memories remain?
The study's authors suggested that fat cell memory may gradually disappear over time, but the timeframe for this process remains unclear.
Human fat cells generally have a lifespan of around 10 years, implying that it could take approximately 10 years for the memory of obesity to be erased from the cells.
This could potentially lead to fat cells to "forget" their predisposition to store nutrients.
The researcher stated that it may become possible in the future to reprogram body fat so that weight is not regained once a person stops dieting or ceases taking weight loss medication.
Maintaining a reduced or healthy body weight for an extended period may be sufficient to erase the memory, but further research is required to confirm this.
Edited by: Zulfikar Abbany
Primary source:
Adipose tissue retains an epigenetic memory of obesity after weight loss, according to a study published in the journal Nature in November 2024 by Hinte, L.C., Castellano-Castillo, D., Ghosh, A. et al.
Author: Fred Schwaller