Diets rich in fiber, plant proteins, and unsaturated fats may beneficially modulate the gut microbiota involved in weight loss

In a recent review published in the Nutrients Journal, researchers looked at existing data to assess the impact of macronutrients and dietary patterns on the gut microbiome among overweight and obese individuals.

Study: Effects of animal and vegetable proteins on the intestinal microbiota in overweight or obese subjects.  Image credit: AntoninaVlasova/Shutterstock.comStudy: Effects of animal and vegetable proteins on the intestinal microbiota in overweight or obese subjects. Image credit: AntoninaVlasova/


Obesity, or adiposity, is an increasingly prevalent multifactorial condition that increases the risk of non-communicable diseases such as cardiovascular disease, metabolic disorders, diabetes and musculoskeletal disorders, degrading quality of life and lowering overall survival.

Microbes in the gut, or gut microbiota, are critical to maintaining health and preventing obesity, identifying which could help develop targeted weight loss strategies based on gut microbial modulation.

About the review

In the present review, researchers determined the association between dietary patterns, the gut microbiome, and obesity.

The PubMed database was searched for clinical studies, original research, meta-analyses and reviews published in English up to February 2023 that evaluated the influence of various macronutrients and dietary patterns on the gut microbiome among overweight or obese individuals and mice.

Additionally, citations from included records were manually searched to identify additional studies.

Studies with protein representing ≥ 20.0% of total daily energy or > 1.30 grams per kg of body weight per day were included. The team excluded studies that included individuals of normal weight, unpublished papers, studies published in a language other than English, or papers with an unspecified protein intake.

Effects of carbohydrates, proteins and fats on the gut microbiome

Consuming carbohydrates such as whole grains or wheat bran can increase your abundance Bifidobacteria AND lactobacilli and increase the genetic richness, while the counts of Eubacterium rectale and the firmicutes TO Bacteroidetes decrease in ratio.

Inulin-type fructans increase levels of short-chain fatty acids (SCFA) and Bifidobacterium adolescents abundance. High resistant starch (RS) and low carbohydrate (WL) diets for weight loss increase Ruminococcus bromii AND Oscillibacter count and decrease Collinsella aerofaciens count.

High-fat diets are associated with an increase Alistipes AND Bacteroids lipopolysaccharide (LPS) counts and levels and decreased Faecalibacterium SCFA counts and levels. Low-fat diets increase fecal abundance Bifidobacteriumand diets high in saturated fat are increasing Faecalibacterium prausnitzii abundance.

Sardine-rich diets decrease the firmicutes TO Bacteroidetes ratio and increase the Bacteroids TO Prevotella relationship. Omega-3 supplementation can elevate Coprococcus AND Bacteroids species and reduce Collinsella species count (related to fatty liver).

Decrease in the consumption of salmon and cod Bacteroidetes abundance, while the consumption of polyunsaturated fatty acids (PUFA) may increase Lachnospiraceae AND Bifidobacterium abundance of species.

Beef-rich diets are on the rise Bacteroides fragilis AND vulgar count and decrease those of Bifidobacterium adolescents.

Consume whey concentrate from fermented milk with Bifidobacterium breve can lower Bacteroides fragilis AND Clostridium perfringens count. High-protein, low-carb diets can decrease Roseburia AND Eubacterium rectale abundance and growth Akkermania counts and intestinal microbial diversity.

Effects of different diets on the gut microbiome

Western diets, characterized by low fiber and high fat, meat and animal food, increase the profile of inflammatory bacteria, i.e. the abundance of nucleated Fusobacterium, Alistipes, Bacteroids, Bilophila, Bifidobacterium, Peptococcusand anaerobic Lactobacillus.

Conversely, the levels of firmicutes which metabolize plant polysaccharides (Ruminococcus bromii, Eubacterium rectaleAND Roseburia) diminish.

Mediterranean diets (MED) are rich in plant-based foods and vegetables, with fish and poultry replacing the intake of lamb and beef, with a limited intake of red and processed meat, 40.0% of total caloric intake per day primarily from unsaturated fat and daily protein and carbohydrate intakes of 123 grams and 80 grams, respectively.

Green-MED diets include daily intakes of green tea and the Mankai plant, rich in polyphenols. Diets increase butyrate-producing, beneficial and anti-inflammatory bacterial counts, genetic richness and bacterial diversity in the gut.

MED diets are on the rise Prevotella, Prevotellacea, Lachnoclostridium, Enterohabdus and Bacteroidetes counts, elevate fecal levels of propionate and butyrate, and enhance the enzymatic degradation of branched-chain amino acids. On the contrary, bifidobacterium, LachnospiraceaeAND Parabacteroides counts are lowered with the reduced enzymatic synthesis of branched chain amino acids.

MED diets increase the levels of fiber degradation Faecalibacterium prausnitzii and genes for the microbial degradation of carbohydrates associated with butyrate metabolism. Vegetarian diets are high in plant protein, and on the rise Streptococcus AND Anaerotypes counts as it decreases Clostridium AND Odoribacter count.

Low-fat vegan diets are associated with an increase Bacteroidetes, Faecalibacterium prausnitziiPrevotella, and diminished Bacteroides fragilis count. Very low calorie ketogenic diets
(VLCKD) consist of approximately 26 grams of daily carbohydrate intake, 40% of total daily energy from fat, and 90 grams of protein per day, approximately 1.20 to 1.40 grams/kg.

VLCKDs increase the abundance of Bacteroidetes, Ruminococcaceae, AND Morigibacteriaceae and decrease that of Firmicutes, Proteobacteria, Enterobacteriaceae, ComamonadaceaAND sinobacteriaceae.


Based on the findings, higher intakes of animal protein and adherence to Western diets may decrease the abundance of beneficial bacteria and increase the abundance of harmful bacteria in the gut, increasing obesity risks.

Conversely, increasing plant protein intake and following the Mediterranean diet increases the count of butyrate-producing anti-inflammatory bacteria, lowers that of pro-inflammatory bacteria, and increases bacterial diversity.

Higher intakes of plant protein, fiber, and adequate amounts of unsaturated fat can modulate the gut microbiome and aid in weight loss.

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