High-protein diets can change gut bacteria, reduce fat

This short-term experimental study lasted four weeks and involved 16 mice.

For the first two weeks, the mice were fed a regular carbohydrate diet. The researchers then switched the mice to four separate protein diet groups for the remainder of the study:

• standard protein diet
• 10% aromatic amino acids
• 10% Branched Chain Amino Acid Diet.
• Diet with 5% aromatic amino acids and 5% branched chain amino acids.

The volume of each diet was the same and contained an equal amount of protein.

The researchers collected daily stool samples and took weekly measurements of body composition to monitor changes in body fat and muscle mass.

They extracted DNA from fecal samples and analyzed it to observe how the mice’s gut bacteria changed throughout the study.

The study found that the gut microbiota responded differently to each type of diet, showing significant changes from the carbohydrate diet to the four different protein diets.

Using machine learning, the researchers could predict with 97% accuracy which protein diet the mice were consuming just by looking at their gut bacteria.

ABOUT MNTAdejumo elaborated on which protein diets specifically resulted in the greatest reduction in fat mass and body weight.

“A combination of 5% branched chain amino acids with 5% aromatic amino acids resulted in the lowest body weight, while [10% aromatic amino acid diet] had the lowest percentage of fat mass, but the greatest weight gain,” he said.

“These results imply that beyond the type of diet, the type of gut microbiome that metabolizes the diet is far more important. Metabolism of the gut microbiome of the diet has the greatest influence on host body composition.”
– Samson Adejumo, Principal Researcher

“The result of the weight [and] body composition is unexpected because branched-chain amino acids are involved in building muscle protein, and we would expect that an increase in [branched-chain amino acid] intake will increase lean mass, not fat mass,” he said.

Further research is needed to confirm whether the protein diets caused all the observed changes in body composition and gut bacteria in the mice.

However, the predictable patterns identified by the researchers suggest a link between protein diets and changes in the gut microbiome.

Adejumo explained how the observed changes in gut microbiota may be related to body composition and weight loss.

he said aromatic amino acidsincluded mainly as precursors of neurotransmitters, are essential for maintaining the normal biological functions of the body.

“In contrast, branched-chain amino acids are involved in maintaining muscle function and protein production in muscle development.”

He further explained:

“Changes in the gut microbiome reflect the bioavailability of essential components in the gut microbiome. Whenever a gut microbiome can utilize dietary components, it will positively affect body composition, specifically, fat mass and lean mass.”

Essentially, changes in gut microbiota can be influenced by the types and amounts of protein consumed, subsequently influencing body composition. This also implies that a healthy gut microbiome may be crucial for maintaining optimal body composition and weight.

MNT also spoke with Alyssa Simpson, RDN, CGN, CLT, a registered dietitian, certified gastroenterologist and owner of Nutrition Resolution in Phoenix, Arizona, who was not involved in the study.

“Changes in gut microbiota can significantly affect body composition and weight loss by changing how efficiently calories are extracted from food,” she said.

She suggested, for example, that a higher ratio of certain bacteria could improve calorie absorption, potentially contributing to weight gain.

Additionally, Simpson noted that “some bacteria produce lipopolysaccharides that can promote inflammation and fat accumulation, while beneficial bacteria can contribute to the maintenance of intestinal barrier integrity and regulation of appetite through the production of hormones and neurotransmitters.”

According to Simpson, more research is needed, but diets high in certain proteins, particularly plant-based proteins, have been shown to improve human gut health and body composition.

“Plant-based protein diets promote gut health by supporting beneficial bacteria and regular bowel movements. They are generally lower in calories and saturated fat compared to animal-based diets, potentially helping with weight management and reducing body fat.”
– Alyssa Simpson, RDN, CGN, CLT

Plant-based diets are also rich in dietary fiber, promoting growth fiber-fermenting microbial species in useful metabolites like short chain fatty acidswhich are associated with numerous health benefits.

Although the body produces them, she also suggests getting dietary sources of amino acids such as glutamine and arginine, which “contribute to maintaining a strong intestinal barrier, preventing harmful substances such as lipopolysaccharides from entering the bloodstream and potentially affect body composition”.

For those looking to improve their gut microbiome, overall health and body composition through diet, Simpson recommends prioritizing “a rich variety of plant-based foods such as fruits, vegetables, nuts, seeds, whole grains and legumes.”

She also advises “moderate protein intake to maintain muscle and metabolic health without excess unhealthy fats.”

Most importantly, “choose a dietary approach that fits your personal preferences, health goals and lifestyle for lasting results,” Simpson emphasized.

Adejumo said, as a next step, “we plan to do some functional analysis and conduct some mechanical experiments to be able to improve the overall health.”

“We also aim to formulate our diets with single amino acids to fully understand the effect of individual amino acids in the diet and to identify specific gut microbial strains involved in protein fermentation,” he added.

While more research is needed and animal studies do not translate directly to humans, learning how fermentation of dietary proteins Affecting gut bacteria can help create personalized diets that modify the gut microbiome to promote better health and weight management outcomes.

“This concept i personalized nutrition “holds promise for broader integration into health care practices, potentially revolutionizing how dietary advice is tailored to optimize health outcomes in diverse populations,” concluded Simpson.