Research
Energy balance
Obesity is associated with an elevated Firmicutes-to-Bacteroidetes ratio in the gut, which decreases following weight loss, although some studies show conflicting results.
Obesity is linked to a higher ratio of Firmicutes to Bacteroidetes bacteria in the gut. This ratio tends to decrease when you lose weight, whether through surgery or diet. However, this is a correlation, not necessarily a cause, and some studies show different patterns. Focus on sustainable weight loss rather than targeting specific bacteria alone.
ModerateQualifiesMEDIUM confidence
One of the early findings was that, in the gut of obese humans and mice, the ratio of Firmicutes to Bacteroidetes is elevated and falls with weight loss.
Why this rating
Multiple studies confirm the correlation, but causality remains unproven.
Source
The Human Gut Microbiome
Timothy E. Sweeney et al. · JAMA Surgery · 2013
DOI 10.1001/jamasurg.2013.5
narrative_reviewCited 245×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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