S. Wang, Z. Bao, Z. Li, M. Zhao, X. Wang and F. Liu (2025). The impact of very-low-calorie ketogenic diets on gut microbiota in individuals with obesity: a systematic review and meta-analysis. Gut microbes, 17(1), 2566305. https://doi.org/10.1080/19490976.2025.2566305

PubMed 41054273

[Abstract]
OBJECTIVE: This study aimed to systematically review and meta-analyze the effects of very-low-calorie ketogenic diets (VLCKD) on gut microbiota in individuals with obesity.

METHODS: A comprehensive literature search was conducted across four electronic databases-PubMed, EBSCOhost, Cochrane Library, and Web of Science-up to June 2025. Outcomes included changes in gut microbial diversity and the relative abundance of key taxa. Subgroup analyses were performed based on body mass index (BMI), age, and intervention duration.

RESULTS: A total of 14 studies were included. Random-effects meta-analysis revealed that VLCKD interventions significantly improved gut microbial α-diversity, as indicated by increased Shannon index (SMD: 0.54, 95% CI: 0.03 to 1.04, P = 0.0378) and Faith's Phylogenetic Diversity (PD) index (SMD: 0.77, 95% CI: 0.36 to 1.18, P = 0.0002). In addition, VLCKD significantly increased the abundance of Akkermansia (SMD: 1.76, 95% CI: 0.48 to 3.03, P = 0.0069) and the Firmicutes-to-Bacteroidetes (F/B) ratio (SMD: 1.01, 95% CI: 0.67 to 1.34, P < 0.0001), while significantly reducing the probiotic genus Bifidobacterium (SMD: -1.23, 95% CI: -1.81 to -0.64, P < 0.0001). Subgroup analyses indicated that the increase in Shannon index was more pronounced in participants with BMI ≤ 30 kg/m² and age >30 years. Akkermansia showed a greater increase in those with BMI 30-35 kg/m², age >40 years, and intervention duration ≤6 weeks. Conversely, Bifidobacterium abundance declined significantly in individuals with BMI 30-35 kg/m², age >40 years, and within an intervention period ≤12 weeks.

CONCLUSION: VLCKD appears to be a promising dietary intervention for modulating gut microbiota in individuals with obesity. However, its bidirectional effects on microbial ecology warrant caution. Future studies should further investigate its long-term safety and explore personalized strategies for microbiota-targeted interventions.