Nature: Why does fat increase after dieting? How protein helps with weight loss

A study led by Professor Zhai Qiwei of the Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, published in the journal Nature Metabolism, showed that the increase in lactic acid bacteria and their metabolites after dieting enhanced intestinal lipid absorption in mice, leading to rapid fat accumulation and obesity
.

Studies have also shown that this effect can be prevented
by a high-protein diet or specific antibiotics that inhibit the growth of lactic acid bacteria in the gut.
An article reviewing this work was published in the News and Opinions section
of Nature Metabolism.

Dietary restriction (DR), often referred to as dieting, is widely used to reduce fat mass and lose weight
by restricting food intake.
However, weight regain after dieting is still a big problem
.

In this study, the researchers used 10 dieting regimens to investigate the effect
of post-diet "supplementation" on fat mass in mice.
All the data suggests that eating after a diet can lead to rapid fat accumulation and obesity
.
Further analysis found that enhanced intestinal lipid absorption, increased lipid anabolism of white adipose tissue (WAT), and decreased total lipid oxidation were the main reasons for
the increase in fat mass after dieting.

To identify potential dietary interventions to prevent fat gain after dieting, the researchers fed mice a high-protein diet, a low-protein diet, or a normal protein diet supplemented with essential amino acids in the post-diet
phase.

The results suggest that a high-protein diet can prevent rapid fat accumulation and obesity, and even partially maintain diet-induced fat loss
.
Paired-feeding experiments with isocalorie normal protein and high-fat feeds have shown that feed composition is more important
than caloric intake in preventing fat gain after dieting.

Further trials also showed that a high-protein diet after dieting reduced levels of bile acids in the gut and serum, weakened intestinal lipid absorption, reduced lipid anabolism in WAT, and increased total lipid oxidation
.

The researchers then analyzed the composition of the gut microbiota and found that the abundance of lactic acid bacteria increased significantly by about 50 percent when fed a normal protein diet after dieting, while this increase was significantly inhibited
when fed a high-protein diet.

The isolated lactobacillus is Lam-1, which is very sensitive
to penicillin.
The researchers found that treating mice with penicillin significantly inhibited the growth of Lam-1, weakened intestinal lipid absorption, reduced fatty acid uptake in WAT, and reduced body fat accumulation
after dieting.

On the other hand, experiments on sterile (GF), sterile (GB) and specific pathogenic (SPF) mice showed that supplementation with Lam-1 or its metabolites significantly promoted intestinal lipid absorption, increasing the absorption of fatty acids in WAT, leading to increased fat mass and obesity
.

This study proves that rerelaxation after DR contributes to the development of obesity and provides an important animal model
for obesity research.
Studies have also shown that targeting lactic acid bacteria with high-protein diets or antibiotics to inhibit intestinal lipid absorption may be an effective strategy
to prevent obesity after dieting.

Whether it's post-diet obesity or "post-holiday" obesity, new research suggests that the health impact of food composition is more important
than many people think.