Impact of a plant-based dietary intervention on gut microbiota composition, inflammatory markers, and metabolic health in overweight adults: a randomized controlled trial.

Project Abstract

This randomized controlled trial investigates the effects of a plant-based dietary intervention on gut microbiota composition, inflammatory markers, and metabolic health in overweight adults over a 12-week period. A total of 180 participants with a body mass index (BMI) 25–34.9 kg/m² were recruited and randomly assigned to either a plant-based diet (PBD) group or an omnivorous control diet (OCD) group, with stratification by sex and baseline BMI. The study combined quantitative clinical assessments, multi-omics gut microbiome profiling, and targeted biomarker analyses to elucidate mechanistic pathways linking diet, microbiota dynamics, and host metabolism. Baseline measurements included anthropometrics, blood pressure, fasting glucose, insulin resistance (HOMA-IR), lipid panels, and inflammatory markers (high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-?). Fecal samples were collected for 16S rRNA gene sequencing and shotgun metagenomics to characterize microbial diversity, composition, functional potential (metabolic pathways, short-chain fatty acid producers), and resistome. Dietary intake was monitored using weighed food records and 24-hour recalls, enabling adherence scoring and nutrient profiling. Physical activity was assessed by accelerometry to control for lifestyle confounders. The primary outcome was change in gut microbiota alpha diversity and beta diversity between the PBD and OCD groups at week 12. Secondary outcomes included alterations in relative abundances of major microbial taxa (e.g., Firmicutes/Bacteroidetes ratio, butyrate-producing genera), functional pathway shifts (butyrate synthesis, bile acid metabolism), and fecal short-chain fatty acid concentrations. Clinical outcomes encompassed changes in body weight, visceral adiposity (via DEXA), waist circumference, blood pressure, lipid parameters, fasting glucose and insulin sensitivity, and inflammatory markers. Additional exploratory analyses assessed correlations between microbiome features, inflammatory status, and metabolic improvements, with mediation analyses evaluating whether microbiota changes mediated metabolic responses to the plant-based diet. The plant-based intervention emphasized whole-food, minimally processed sources rich in fiber, phytonutrients, and unsaturated fats, with individualized counseling to optimize adherence. The OCD served as a control reflecting habitual omnivorous dietary patterns. Statistical models included mixed-effects regression to handle repeated measures, adjusting for age, sex, baseline BMI, medication use, and physical activity. Differential abundance testing and longitudinal trajectory analyses identified taxa and pathways significantly modulated by the diet. Robust sensitivity analyses addressed potential biases from dropout and non-adherence. Results are anticipated to show that the PBD increases gut microbial diversity and promotes a distinct enterotype associated with enhanced production of short-chain fatty acids, particularly butyrate, accompanied by reductions in pro-inflammatory markers and improvements in insulin sensitivity and lipid profiles. We expect attenuated inflammation to parallel favorable shifts in microbial functions related to bile acid metabolism and carbohydrate fermentation, contributing to weight loss and cardiometabolic risk reduction. The findings will illuminate microbiota-mediated mechanisms underpinning the health benefits of plant-based eating in overweight adults and inform dietary guidelines targeting gut microbiome–host metabolic axis optimization.

Project Overview

What This Project Is About

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The project examines how a plant?based diet affects gut microbiota (the tiny organisms living in the intestine), inflammatory markers (signals in the body that indicate inflammation), and overall metabolic health in adults who are overweight. It compares a plant?based plan to a standard diet to see which approach improves health signals.

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The Problem It Addresses

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Many adults who are overweight face higher risks of inflammation and metabolic problems like high blood sugar or bad cholesterol. The link between diet, gut bacteria, and health is not fully understood. This project tests whether shifting to more plant foods can shift gut bacteria in a way that lowers inflammation and improves metabolic health.

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Objectives of the Project

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1. Describe how a plant?based diet changes gut bacteria composition.
2. Measure changes in inflammatory markers before and after the diet.
3. Assess improvements in metabolic health indicators (e.g., blood sugar, lipids, body weight).
4. Compare outcomes with a control group on a usual diet.

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What You Will Do Step by Step

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1. Review existing studies on diet, gut microbiota, and inflammation.
2. Recruit overweight adult participants and assign them to two groups.
3. Implement a plant?based dietary plan for the intervention group and monitor adherence.
4. Collect stool samples to analyze gut bacteria and blood tests for inflammatory and metabolic markers.
5. Compare pre? and post?diet results within and between groups.
6. Interpret findings in the context of health implications and limitations.

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Expected Outcome

We expect the plant?based group to show a more favorable gut microbiota profile, lower inflammatory markers, and improvements in metabolic health measures, suggesting dietary shifts can benefit overweight adults.