Obesity and Adiposity

Research status: Medium

Multiple studies in vivo and in animal models suggest a strong relationship between bacterial activity in the gut microbiome and adiposity and obesity.

The limited studies performed in humans suggest both probiotics and prebiotics can lower adiposity. Additionally, distinct patterns in the diversity and constitution of gut microbiota were observed in the biota of lean vs. obese human subjects.

Studies in mice show a significant, clear and profound metabolic relationship between gut biome composition and adiposity.

However the link in humans requires further well-designed clinical trials to clarify the association.

Selected scientific literature:

1. [Human] Prebiotics Reduce Body Fat and Alter Intestinal Microbiota in Children Who Are Overweight or With Obesity
  • “Participants were randomly assigned to groups given either oligofructose-enriched inulin (OI; 8 g/day; n=22) or maltodextrin placebo (isocaloric dose, controls; n=20) once daily for 16 weeks. OI group had significant decreases in body weight z-score (decrease of 3.1%), percent body fat (decrease of 2.4%), and percent trunk fat (decrease of 3.8%) compared with placebo (increase of 0.5%, increase of 0.05%, and decrease of 0.3%, respectively). OI also had a significant reduction in level of interleukin 6 from baseline (decrease of 15%) compared with the placebo group (increase of 25%), and a significant decrease in serum triglycerides (decrease of 19%). 16S rRNA sequencing revealed significant increases in species of the genus Bifidobacterium and decreases in Bacteroides vulgatus within the OI group.“
2. [Human] Dissecting the role of the gut microbiota and diet on visceral fat mass accumulation
  • "Our results suggest that while the role of certain nutrients on VFM [visceral fat mass] appears to depend on gut microbiota composition, specific gut microbes may affect host adiposity regardless of dietary intake. The findings imply that the gut microbiota may have a greater contribution towards shaping host VFM than diet alone. Thus, microbial-based therapy should be prioritised for VFM reduction in overweight and obese subjects."
3. [Human/Mice] Gut Microbiota from Twins Discordant for Obesity Modulate Metabolism in Mice
  • Ridaura et al. studied the impact of transferring the fecal microbiota from twin pairs discordant for obesity (i.e., one twin had a normal body mass index, while the other twin was obese) on mouse metabolism. On average, mice receiving the fecal microbiota from obese twins were characterized by a 10% to 15% increase in fat mass (as measured by quantitative magnetic resonance) after 4 to 5 weeks of colonization.

4. [Human/Mice] Roux-en-Y Gastric Bypass and Vertical Banded Gastroplasty Induce Long-Term Changes on the Human Gut Microbiome Contributing to Fat Mass Regulation

  • "Bariatric surgery is currently the most effective procedure for the treatment of obesity. Given the role of the gut microbiota in regulating host metabolism and adiposity, we investigated the long-term effects of bariatric surgery on the microbiome of patients randomized to Roux-en-Y gastric bypass or vertical banded gastroplasty and matched for weight and fat mass loss. The two surgical procedures induced similar and durable changes on the gut microbiome that were not dependent on body mass index and resulted in altered levels of fecal and circulating metabolites compared with obese controls. By colonizing germ-free mice with stools from the patients, we demonstrated that the surgically altered microbiota promoted reduced fat deposition in recipient mice. These mice also had a lower respiratory quotient, indicating decreased utilization of carbohydrates as fuel. Our results suggest that the gut microbiota may play a direct role in the reduction of adiposity observed after bariatric surgery."