Effects of a combined energy restriction and vigorous-intensity exercise intervention on the human gut microbiome: A randomised controlled trial
Exercise and calorie restriction are well known to improve metabolic health, but scientists are still uncovering how these changes happen. One possibility is the gut microbiome — the community of bacteria living in our digestive system.
In a recent study, they tested this idea in 30 sedentary adults with overweight or obesity. Over three weeks:
- Intervention group (18 participants): Reduced calorie intake by about 5,000 kcal per week and added treadmill walking to burn an extra 2,000 kcal per week.
- Control group (12 participants): Continued their usual lifestyle.
They measured body composition (DEXA scans), collected blood, fat, muscle, and stool samples, and analyzed the gut microbiome using advanced genetic sequencing.
Findings:
- Participants in the intervention group lost weight (–2.6 kg on average) and fat mass (–1.5 kg).
- Blood markers improved significantly, including lower insulin, leptin, and cholesterol, with better insulin sensitivity.
- Surprisingly, the gut microbiome didn’t change — neither in diversity nor in bacterial composition.
Key Points
- Alterations in the gut microbiome may contribute to metabolic benefits from weight loss, but few robust randomized controlled trials (RCTs) have investigated this.
- They conducted a parallel-group RCT to determine whether a 3-week intervention combining energy restriction and vigorous-intensity exercise in individuals with overweight or obesity was associated with changes in gut microbiome composition, functional potential, short-chain fatty acid levels, and expression of host–microbiome interaction genes in skeletal muscle and subcutaneous adipose tissue.
- Despite significant improvements in body composition and metabolic health, the gut microbiome remained largely unchanged following the intervention.
These results suggest that early metabolic improvements during weight loss are unlikely to be driven by changes in the gut microbiome.
