A Daily Probiotic Shrank Waist Size and Shifted Sex Hormones in 12-Week Trial

A single probiotic strain, taken daily for three months, shrank waist circumference, lowered leptin, and shifted sex hormone levels in overweight women, according to a new randomized controlled trial published in the Journal of Functional Foods. The results are preliminary, but they raise an intriguing possibility: that gut bacteria may do more than influence digestion, they may talk directly to the endocrine system in women carrying excess weight.

Lactobacillus gasseri LG08 reduced body weight and waist circumference

Keke Chen and colleagues randomized 105 women aged 18 to 50, all with a BMI of at least 25, to receive either 30 billion CFU per day of Lactobacillus gasseri LG08, deposited in the German Collection of Microorganisms and Cell Cultures under accession number DSM 35054, or a dextrin placebo. After 12 weeks, the LG08 group showed statistically significant reductions in body weight, BMI, waist circumference, and hip circumference compared to the placebo group (p < 0.001 for the waist and hip measures). No clinically relevant adverse effects were observed.

This strain belongs to a species with a growing track record. Earlier research on Lactobacillus gasseri SBT2055 and body composition found reductions in BMI, waist circumference, and body fat mass in people with overweight and obesity, and a meta-analysis of probiotic efficacy in overweight and obese adults found that single-strain, high-dose interventions tended to show the most pronounced effects on body weight and waist circumference. LG08's 30 billion CFU dose fits squarely in that high-dose category.

Appetite hormones and sex hormones both shifted with supplementation

The endocrine findings are where this trial becomes particularly notable. Women who received LG08 saw significant increases in GLP-1 (glucagon-like peptide-1) and PYY (peptide YY), two gut-derived satiety signals that slow gastric emptying and reduce appetite (both p < 0.001). At the same time, serum leptin, which is typically elevated in obesity and reflects excess adipose tissue mass, fell significantly in the LG08 group (p < 0.001). Leptin resistance is a well-known feature of obesity, and a drop in leptin alongside actual weight loss suggests the relationship between fat tissue and hormonal signalling may have partially reset.

Beyond appetite regulation, estradiol (E2) and prolactin (PRL) both decreased significantly in the LG08 group (p < 0.01 and p < 0.05, respectively). Obesity is associated with elevated estrogen production from adipose tissue and a range of other hormonal disruptions; obesity's broad impact on female endocrine function has been well characterized, including links to polycystic ovarian syndrome and altered reproductive cycling. Whether the hormonal shifts seen here reflect direct probiotic effects or are secondary to even modest weight loss is a question the study cannot answer.

The trial also captured psychological outcomes. Self-Rating Anxiety Scale and Self-Rating Depression Scale scores both improved significantly in the LG08 group (both p < 0.05), as did Menstrual Distress Questionnaire scores (p = 0.0023). These findings are consistent with a gut-brain axis effect, though again, disentangling the contribution of weight change from a direct microbial influence on mood requires further work.

How the gut microbiome shifted during the 12-week intervention

Using 16S rRNA gene sequencing, the researchers tracked changes in gut microbial composition at baseline and after 12 weeks. LG08 supplementation did not significantly alter alpha-diversity metrics, meaning the overall richness and evenness of the microbiome stayed relatively stable. At the phylum level, Actinobacterota abundance was higher in the LG08 group post-intervention (p < 0.05). At the genus level, relative increases were observed in Bifidobacterium, Phascolarctobacterium, and Enterocloster.

Correlation analyses revealed some suggestive patterns. Parabacteroides abundance was negatively correlated with both body weight (Spearman's rho = -0.285, p = 0.0043) and BMI (rho = -0.268, p = 0.0074). Bifidobacterium abundance correlated positively with estradiol levels (rho = 0.310, p = 0.0018), and Phascolarctobacterium correlated positively with leptin (rho = 0.291, p = 0.0034). These associations are exploratory, and the authors are careful to note they cannot support causal inference. A broader meta-analysis of probiotics and metabolic parameters in overweight women similarly found associations between gut microbiota changes and improvements in waist circumference and insulin levels, without being able to pin down the underlying mechanism.

Limitations that temper the findings

Several constraints limit what can be concluded from this trial. The 12-week follow-up is relatively short, and whether the weight and hormonal effects persist beyond supplementation is unknown. The study enrolled only overweight women, so the results do not apply to men, lean individuals, or women outside the 18 to 50 age range. Crucially, the researchers did not collect objective data on energy intake, macronutrient composition, or physical activity, making it impossible to rule out dietary or lifestyle changes as partial explanations for the observed effects. Detailed sociodemographic variables, including smoking, alcohol use, and sleep, were also not systematically assessed.

The 16S rRNA sequencing approach identifies which microbes are present but cannot directly infer what those microbes are doing; no metabolomic profiling was performed. The correlations between specific genera and hormonal markers are intriguing but remain correlational.

What comes next for LG08 and probiotic weight management research

The trial provides a reasonable proof-of-concept for LG08 as a candidate in weight management research, particularly given its effects on appetite hormones and menstrual distress scores alongside anthropometric measures. Larger trials with longer follow-up, dietary tracking, and metabolomic profiling would be needed to understand the mechanisms involved and to establish whether the hormonal shifts are clinically meaningful.

More broadly, the gap between promising probiotic findings and confirmed therapeutic use remains wide, and researchers have noted that study design variability makes cross-trial comparisons difficult. LG08 joins a growing list of strains that warrant deeper investigation, but it is not yet a treatment. For now, the finding that a single well-characterized probiotic strain can simultaneously move body weight, appetite hormones, and menstrual symptoms in a rigorous randomized trial is enough to justify the next, larger study.

Evidence rating

EMERGING — 84/100

Caveats:

• Single trial with 105 participants; results need independent replication in larger, longer studies before clinical recommendations can be made.
• Restricted to overweight women aged 18–50; findings may not generalize to men, older adults, or other BMI categories.
• Diet, physical activity, sleep, and other lifestyle variables were not objectively measured and could confound outcomes.
• Microbiota–hormone correlations are exploratory and cannot establish causation.
• 12-week follow-up does not indicate whether benefits persist long-term.

Randomized, double-blind, placebo-controlled trial (n=105 overweight women, 12 weeks). Demonstrates statistically significant improvements in BMI, anthropometric measures, satiety hormones (GLP-1, PYY), leptin, and sex hormones with L. gasseri LG08 versus placebo. Microbiota–hormone correlations are exploratory and do not establish causation. The trial has not yet been independently replicated, and the absence of dietary monitoring limits interpretation of metabolic outcomes.

References

1. Keke Chen, Yongmei Qi, Zhiying Wang, et al. (2026). Impact of Lactobacillus gasseri LG08 on weight management and endocrine function in overweight women: A randomized clinical trial. Journal of Functional Foods. https://doi.org/10.1016/j.jff.2026.107389
2. Michał Wiciński, Jakub Gębalski, Jakub Gołębiewski, Bartosz Malinowski (2020). Probiotics for the Treatment of Overweight and Obesity in Humans—A Review of Clinical Trials. Microorganisms. https://doi.org/10.3390/microorganisms8081148
3. Shuying Liu, Kani Ouyang, Xuelian Fang, Huijuan He, Mengying Li (2026). Efficacy of probiotic supplementation for body weight management in overweight and obese adults: a meta-analysis of randomized controlled trials predominantly from East Asia. Frontiers in Public Health. https://doi.org/10.3389/fpubh.2026.1767108
4. Endocrine Changes in Obesity – Endotext – NCBI Bookshelf – NIH. NIH. https://www.ncbi.nlm.nih.gov/books/NBK278973/
5. Ning Cao, Feiyan Zhao, Lai-Yu Kwok, Huan Wang, Zhihong Sun (2024). Impact of probiotics on weight loss, glucose and lipid metabolism in overweight or obese women: A meta-analysis of randomized controlled trials. Current Research in Food Science. https://doi.org/10.1016/j.crfs.2024.100810
6. Yichen Cai, Pan Liu, Xiaolan Zhou, Jun Yuan, Qiu Chen (2023). Probiotics therapy show significant improvement in obesity and neurobehavioral disorders symptoms. Frontiers in Cellular and Infection Microbiology. https://doi.org/10.3389/fcimb.2023.1178399