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The Yo-Yo Effect and Metabolic Memory
The beginning of the new year is synonymous with making good resolutions and lifestyle changes for many people. Popular diets are followed in the hopes of improving health and losing weight. However, maintaining this weight loss is a considerable challenge. The weight lost is often regained and another restrictive diet is put in place. When the weight goes down and up cyclically, it is called the yo-yo effect. Is this difficulty in maintaining the weight loss due to lifestyle and motivation only?
The body that defends itself against weight changes
The physiological barriers to the long-term treatment of obesity are still largely unknown. The body seems to struggle with weight variations. Hypotheses are put forward in connection with physiological mechanisms of counter-regulation to preserve energy (decrease in energy expenditure, increase in intake and an alteration in communication between the brain and organs). But there may be more to it as well.
Research recently published in the Nature journal sheds light on the concept of “metabolic memory”, a mechanism by which the body remembers and attempts to return to its previous weight. For this research, adipocytes (cells that store fat) were biopsied from 20 individuals with obesity but without metabolic disease, before and after bariatric surgery that caused substantial weight loss (defined as a reduction of at least 25% in body mass index). These data were compared to those of individuals who had never been obese. The results show that obesity leads to changes in the cells and DNA of adipose tissue. These changes persist even after significant weight loss.
Some of the genetic research presented in this same article includes tests done in obese mice that have lost weight as compared to non-obese mice. Again, we see that the metabolic memory of obesity persists after weight loss, thus contributing to the pathophysiology of rebound obesity in mice.
However, the generalization of the results of this study is limited since the human participants had all undergone bariatric surgery, a treatment that is obviously not accessible to everyone. This type of surgery also impacts on the human body, such as the gut microbiome and micronutrient absorption, in addition to rapid weight loss, unlike other methods. Also, there is a limitation to the comparison that can be made between the data on mice and humans. More research is needed to shed light on whether other treatments for obesity might erase or reduce this metabolic memory.
The potential dangers of yo-yoing
The risks of weight gain and loss cycles are not always clear in research. Some studies have identified the yo-yo effect as a predictor of the onset of diabetes while others do not report a link between the two. An association could also exist between repeated weight variations and hyperphagic behaviors, or food cravings.
On the other hand, the amount of good bacteria that colonize the intestines is reduced after following a restrictive diet. Indeed, a study reveals a specific signature of the microbiome (bacteria found in the intestines) that persists after weight loss and that the microbiome could have a role to play in accelerated weight regain after a diet. These changes in the microbiome following a diet (e.g. a decrease in flavonoid levels) would contribute to the reduction of energy expenditure leading to secondary weight gain. Despite this, people who want to lose weight should not be discouraged from doing so since the benefits can outweigh the risks.
Author
A University of Montreal graduate and holding a Master's Degree in Medical Research from Griffith University in Australia, Tracy is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ). With more than 15 years of experience, she likes to share her knowledge about food in a simple and illustrated way in order to support you in achieving your health goals. Her approach combines the pleasure of eating, intuitive eating and mindfulness. Tracy specializes in adapted nutrition for chronic diseases, weight loss, gastrointestinal health, vegetarianism and veganism.
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