Research
Mixed
Short-term consumption of fast-food meals (a subset of UPFs) increases bile-tolerant bacteria (Collinsella, Parabacteroides, Bilophila) and decreases fiber-fermenting bacteria (Lachnospiraceae, Butyricicoccus).
Eating fast food for just 4 days can shift your gut bacteria, increasing bile-tolerant types and decreasing fiber-fermenting types. To maintain a healthy microbiome, limit fast food frequency and prioritize fiber-rich foods.
GoodSupportsMEDIUM confidence
A randomized cross-over trial of ten healthy subjects consuming a fast-food (i.e., burgers and fries) or Mediterranean diet for 4 days each... showed increases in bile-tolerant bacteria, including Collinsella spp., Parabacteroides spp., and Bilophila wadsworthia, and decreased fiber-fermenting bacteria, including Lachnospiraceae spp. and Butyricicoccus spp., after the fast-food diet
Why this rating
Based on a randomized cross-over trial, which is higher quality than the observational studies, though sample size is small (n=10).
Source
Ultra-Processed Foods: A Narrative Review of the Impact on the Human Gut Microbiome and Variations in Classification Methods
Allison L. Brichacek et al. · Nutrients · 2024
DOI 10.3390/nu16111738
narrative_reviewCited 41×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- High consumption of ultra-processed foods (UPFs) is associated with specific alterations in gut microbiota composition, including decreased Lachnospira and Ruminococcus species and increased Prevotella species, though effects on overall microbial diversity (alpha/beta) are inconsistent across studies.Moderate
- High consumption of ultra-processed foods is associated with negative health outcomes including increased depression/anxiety, higher BMI/weight, and decreased HDL cholesterol, particularly in men consuming >5 servings/day.Moderate
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