Lactobacillus gasseri: Uses, Benefits, Dosage & Safety
Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
Quick summary
L. gasseri is the probiotic most associated with weight and abdominal fat, on the strength of Japanese trials showing modest visceral fat reductions. The results are real but small, strain-specific, and — importantly — reversed when supplementation stopped.
What is Lactobacillus gasseri?
Lactobacillus gasseri (now reclassified as Lactobacillus gasseri within the reorganised Lactobacillaceae) is a species native to the human gut and vaginal microbiome. The weight research centres on specific strains, principally SBT2055 and BNR17.
What Lactobacillus gasseri is commonly used for
Abdominal and visceral fat reduction, general gut health, and vaginal and urinary microbiome support.
How Lactobacillus gasseri works
Proposed mechanisms include reduced dietary fat absorption, effects on inflammatory signalling in adipose tissue and influence on appetite-regulating hormones. None is firmly established in humans; the clinical results came first and the mechanism remains somewhat inferred.
What the evidence says
Each claim below is tied to the specific study behind it, rather than to a general reading list.
- Twelve weeks of L. gasseri SBT2055 reduced abdominal visceral fat by around 4.6% in adults with obesity. Kadooka et al., European Journal of Clinical Nutrition, 2013 — randomised, double-blind, placebo-controlled trial. (PubMed)
- Effects on abdominal fat reversed after supplementation stopped. Kadooka et al., British Journal of Nutrition, 2010 — randomised controlled trial with follow-up. (PubMed)
- Meta-analysis of Lactobacillus strains for weight found small and strain-dependent effects. Borgeraas et al., Obesity Reviews, 2018 — systematic review and meta-analysis. (PubMed)
Typical dosage used in studies
Trials used around 108–1010 CFU daily of a named strain, typically in fermented milk or capsules, over 12 weeks.
Side effects and safety
Well tolerated. Mild digestive symptoms in the first weeks are the usual complaint. Immunocompromised people should get advice before taking live cultures.
Medication interactions and who should avoid Lactobacillus gasseri
Medication & safety check
No established drug interactions. Space doses away from antibiotics.
General information, not personal medical advice. If you take any medication, confirm it is safe to combine with Lactobacillus gasseri with your doctor or pharmacist first.
Sources & further reading
The claim-level citations above are drawn from these sources:
- Kadooka et al., European Journal of Clinical Nutrition, 2013 — randomised, double-blind, placebo-controlled trial — find on PubMed
- Kadooka et al., British Journal of Nutrition, 2010 — randomised controlled trial with follow-up — find on PubMed
- Borgeraas et al., Obesity Reviews, 2018 — systematic review and meta-analysis — find on PubMed
- NIH Office of Dietary Supplements
- NIH National Center for Complementary and Integrative Health
Frequently asked questions
How much weight does it actually cause you to lose?
Very little. The headline trial showed roughly a 4–5% reduction in visceral fat area over 12 weeks, alongside about a kilogram of body weight. Real, measurable, and far from what the marketing implies.
Do the effects last?
Not on their own. When supplementation stopped in the follow-up study, the abdominal fat measurements drifted back. That makes it an ongoing cost, not a fix.
Does the strain matter?
Enormously. The evidence attaches to SBT2055 and BNR17 specifically. A product listing 'L. gasseri' with no strain has no studies behind it.
Where you'll find Lactobacillus gasseri
Lactobacillus gasseri appears in Gut, Weight & Probiotics formulas. Browse the supplement guides to see the products we review, each with a full breakdown of formula, pricing and safety.
Related ingredients to explore
Ingredients often studied or formulated alongside Lactobacillus gasseri.
General information, not medical advice.