High-protein diets may keep weight loss results consistent, study finds

06 Dec 2022 --- A new study led by researchers from the Shanghai Institute of Nutrition and Health of the Chinese Academy of Sciences purports that a high-protein diet and specific antibiotics can prevent weight gain after dieting when most individuals gain the weight back.

The recommendation comes on the back of findings that show that an increase of Lactobacillus and its metabolites after dieting enhanced intestinal lipid absorption leading to quick fat accumulation. A high-protein diet inhibits the growth of intestinal Lactobacillus.

The experiments conducted on mice demonstrate why fat is gained after dieting. The results showed that the high-protein diet prevented quick fat mass accumulation and obesity and even partially maintained the fat loss induced by dieting. 

Sustained weight loss and weight maintenance are key challenges in treating obesity. Studies found that weight in young children from low-income households increased in the first six months of the COVID-19 global pandemic, while weight gain was highest among those already considered severely obese before the pandemic.

The World Health Organisation recently warned that more than half of the EU’s adult population is overweight or obese, prompting stronger calls for tougher regulations and better nutrition labeling. 

Dietary recommendations
The study, “High-protein diet prevents fat mass increase after dieting by counteracting Lactobacillus-enhanced lipid absorption,” published in Nature Metabolism, demonstrates that refeeding after dietary restriction (DR) contributes to the development of obesity.

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.

Refeeding after DR provides important animal models for obesity research. It also suggests that using a high-protein diet or antibiotics to target Lactobacillus and inhibit intestinal lipid absorption is likely an effective strategy for preventing obesity after dieting. A high-protein diet prevented quick fat mass accumulation and obesity, according to a study conducted by the Shanghai Institute of Nutrition and Health. 

Further tests revealed that a high-protein diet after dieting reduced the levels of bile acids in the intestine and in serum, reduced intestinal lipid absorption, decreased lipid anabolism in WAT and increased total lipid oxidation.

The researchers then analyzed the composition of intestinal microbiota. They found that refeeding with a normal-protein diet after dieting dramatically increased the abundance of Lactobacillus by about 50%. This increase was markedly suppressed when refed with a high-protein diet. 

The experiment
In this study, led by Professor Zhai Qiwei, the researchers used ten dieting protocols to investigate the effect of post-diet “refeeding” on fat mass in mice. The data demonstrated that refeeding after dieting leads to quick fat mass accumulation and obesity.

Further analysis revealed that enhanced intestinal lipid absorption increased lipid anabolism in white adipose tissue (WAT), and decreased total lipid oxidation are the main causes of fat mass increase after dieting.

To identify potential dietary interventions to prevent fat mass increase after dieting, the researchers fed mice either a high-protein, low-protein, or normal-protein diet supplemented with essential amino acids during the post-dieting phase.Maintaining weight loss is one of the main challenges in treating obesity.

Pair-feeding experiments involving equal-calorie normal-protein or high-fat diets showed that diet composition was more important than caloric intake in blocking fat mass increase after dieting.

Effect of penicillin ingestion
The Lactobacillus bacteria were isolated and identified as Lam-1, which is very sensitive to penicillin. The researchers discovered that treating the mice with penicillin significantly inhibited the growth of Lam-1, reduced intestinal lipid absorption, decreased fatty acid uptake in WAT, and minimized body fat accumulation after dieting.

On the other hand, tests on germ-free, gnotobiotic and specific-pathogen-free mice showed that supplementing with Lam-1 or its metabolites significantly enhanced intestinal lipid absorption, increased fatty acid uptake in WAT and led to fat mass increase and obesity.

The results of this study highlight the need for more information on the driving factors behind these metabolic changes in the fight against obesity.

By Inga de Jong