How to sustain the effects of a diet? Overweight and obesity are essentially caused by an imbalance between the calories ingested and the calories expended. There are also added environmental factors and genetics. Food restriction – through more or less strict diets – is therefore a strategy frequently used by people who wish to losing weight, including those suffering from obesity. The hardest part is often not so much losing weight. On the contrary, it is rather to maintain its new weight over time. However, weight regain after dieting is common and the underlying mechanisms remain largely unknown. In a news study published in Nature metabolismresearchers show that in mice, a high-protein diet after weight loss can counter the phenomenon, via a process dependent on the intestinal microbiota.
After a diet, the body “takes revenge”
Obesity – whose global prevalence has nearly tripled since 1975 – dramatically increases the risk of disease. These can be type 2 diabetes, fatty liver disease, cardiovascular disease, several cancers and even COVID-19! It is therefore important to do everything possible to regain a normal body mass index (BMI) and thus protect yourself from these diseases.
Unfortunately, it appears thatafter a diet, especially a diet that is a little too restrictive, the body “takes revenge”. It accumulates fat quickly. This affects appetite and thermogenesis. It is the bodily process that produces heat by consuming calories. To better understand what drives or maintains the observed metabolic changes in response to weight loss, Chinese nutrition researchers conducted a few experiments on mice.
Read also: Binge eating disorder: a serious eating disorder that is often overlooked!
Mice fed a diet for three days – b) 10, 25 and 65% food, or c) 65, 25 and 10% food, from day 1 to 3 respectively – showed an increase in fat mass from normal food recovery. They also tended to consume more food than the mice in the control group (in blue). Credits: Zhong et al., Nature metabolism (2022)
They devised ten types of diets, to which they subjected the rodents. They then studied the effect of refeeding after each diet on fat mass. All data showed that refeeding (after a three-day food restriction) induced rapid fat accumulation in mice. In addition, the increased absorption of intestinal lipids contributed to the increase in post-diet fat mass.
Lactobacilli cause fat accumulation
The team therefore tested various dietary interventions aimed at preventing this increase in post-diet fat mass. After food restriction, they subjected the mice to three kinds of diets. A high protein diet, a low protein diet or a normal protein diet supplemented with essential amino acids. The results showed that the high protein diet prevented the rapid accumulation of fat mass. It even partially maintained the fat loss induced by the previous diet.
A high-protein (HP) diet maintained the fat mass loss induced by the 3-day food restriction (SDR) with a food intake of 10, 25 and 65% from day 1 to day 3. The low-protein diets (LP, in purple) and normally protein (NP, in blue), did not have this effect. Credits: Zhong et al., Nature metabolism (2022)
The researchers then analyzed the composition of the gut microbiota mice. They found that refeeding a ‘normal’ protein diet after dietary restriction significantly increased the amount of bacteria Lactobacillus, up to about 50%! However, this increase was not observed in the case of refeeding on the basis of a high protein diet. Lactobacilli therefore necessarily play a role in weight regain.
Read also: What if our intestinal microbiota made us addicted to sugar?
To verify this, the researchers treated some mice with penicillin. It is an antibiotic to which lactobacilli are particularly sensitive. The treatment significantly inhibited the growth of these bacteria. It therefore produced effects similar to those of a high-protein diet. It decreased the intestinal absorption of lipids, decreased the absorption of fatty acids in white fat, and reduced the accumulation of body fat after dieting.
Conversely, experiments have shown that supplementation with lactobacilli and its metabolites causes opposite effects. In particular, an increase in fat mass was observed. The researchers believe it is likely that the same process takes place in the human intestines.
Penicillin, a potential treatment to prevent weight regain?
The team points out that during their experiments with mice, they could see that the composition of foods eaten after weight loss – specifically the level of protein they contained – was more important than calorie intake. to avoid fat increase.
So this study has potentially shed light on why many people have such a hard time maintaining weight loss. It wouldn’t be because they eat more or exercise less. But well because their microbiota has undergone a fundamental change. The latter is characterized among other things by a significant increase in lactobacilli. This promotes the intestinal absorption of fats.
Read also: An anti-hunger molecule is formed during intensive physical activity
Thus, certain dietary practices known to be healthy, such as the practice of intermittent fasting – which consists of alternating more or less long periods of fasting with periods of food intake – could encourage the intestine to increase its capacity to extract fat from the body. ‘food. ” Diets should always be encouraged to reduce fat and control body weight. However, the harmful effects of stopping a diet on weight regain and obesity must be seriously taken into account. “, warn the researchers.
In addition, penicillin is able to limit the growth of lactobacilli. This antibiotic is now emerging as a potential way to prevent weight gain after dieting. Additional studies, conducted on humans and over a longer period, are however necessary before confirming that the effects observed here on mice are applicable to humans.