The answer
Only a little, in the trials so far. A 2018 meta-analysis of 15 randomized trials in 957 adults with a BMI of 25 or more found that probiotics lowered body weight by 0.60 kg more than placebo over 3 to 12 weeks, an effect its authors called small.1 A 2019 review of 19 trials found no difference in weight or BMI,2 and NIH calls the trial results inconsistent.3
In short
- Across 15 trials, probiotics lowered body weight by 0.60 kg, BMI by 0.27 points and body fat percentage by 0.60 points more than placebo; body fat in kilograms did not change significantly.1Borgeraas et al., 2018
- A 2019 review of 19 trials and 1,412 adults found no difference in weight or BMI and a 0.82 cm smaller waist, on low to moderate quality evidence.2Suzumura et al., 2019
- Of 14 trials of Lactobacillus strains, 9 found lower weight or body fat, 3 found no effect and 2 found weight gain; the reviewers call the benefit strain dependent.4Crovesy et al., 2017
- In a 12-week trial of 210 adults, visceral fat area fell about 8% from baseline on fermented milk with Lactobacillus gasseri SBT2055, and the effect weakened within 4 weeks of stopping.5Kadooka et al., 2013
- CDC says people whose weight loss is gradual and steady, about 1 to 2 pounds a week, are more likely to keep the weight off.6CDC
What did meta-analyses of probiotic trials find for weight loss?
Small changes, if any. The 2018 meta-analysis found a 0.60 kg difference, about 1.3 pounds, with a confidence interval running from 0.01 to 1.19 kg; the 2019 review found weight fell 0.54 kg more on probiotics or synbiotics, a difference that was not statistically significant. A 2026 meta-analysis of 10 trials also found no significant change in body weight.1,2,7
| Review | Trials and people | How long | Body weight | Other measures | Source |
|---|---|---|---|---|---|
| 2018 meta-analysis | 15 randomized trials, 957 adults, 63% women, mean BMI 27.6 | 3 to 12 weeks | 0.60 kg lower than placebo | BMI 0.27 lower; body fat percentage 0.60 points lower; fat mass no significant change | Borgeraas et al. 1 |
| 2019 review | 19 randomized trials, 1,412 adults, probiotics or synbiotics | Not stated in the abstract | 0.54 kg lower, not significant (moderate quality evidence) | BMI no difference (low quality); waist 0.82 cm smaller (low quality) | Suzumura et al. 2 |
| 2017 review | 14 trials of Lactobacillus strains, 1,067 people | 3 weeks to 6 months | Lower weight or body fat in 9 trials, no effect in 3, weight gain in 2 | Results depended on the strain | Crovesy et al.; NIH ODS 4,3 |
| 2026 meta-analysis | 10 randomized trials, 633 adults, probiotics or synbiotics | 8 to 12 weeks | No significant change | BMI and body fat fell, but both effects weakened or lost significance when one trial was left out | Ko et al. 7 |
Sources 1 to 4 and 7, linked below. Each review studied adults with a BMI of 25 or more, the 2018 review's cutoff for overweight; differences are against placebo or control groups. 0.60 kg is about 1.3 pounds.
NIH's Office of Dietary Supplements, summing up the 2018 analysis, says the effects "were small and of questionable clinical significance."3 Its own table of weight-loss supplement ingredients sums up the probiotic research as inconsistent effects on body fat, waist and hip circumference, and body weight, with gas as the reported side effect.3
Does Lactobacillus gasseri help with weight loss?
Two strains of it have trials, with mixed results. In two 12-week Japanese trials, fermented milk with L. gasseri SBT2055 lowered visceral fat area, measured by CT scan, by 4.6% and by about 8% from baseline. In two 12-week Korean trials of the strain BNR17, waist size fell, but in the first one, body weight did not differ from placebo.8,5,9,10
| Strain and trial | Who took part | Dose and length | What changed | What did not | Source |
|---|---|---|---|---|---|
| L. gasseri SBT2055, 2010, Japan | 87 adults with a BMI of 24.2 to 30.7 and a large visceral fat area | 200 g a day of fermented milk, 12 weeks | Visceral fat area down 4.6% and body weight down 1.1 kg from baseline | In the control milk group, none of the measures fell significantly | Kadooka et al. 8 |
| L. gasseri SBT2055, 2013, Japan | 210 healthy adults with large visceral fat areas | 200 g a day of fermented milk with 10 million or 1 million CFU per gram, 12 weeks | Visceral fat area down 8.5% and 8.2% from baseline; BMI, waist, hip and body fat mass also fell | The changes weakened within 4 weeks of stopping | Kadooka et al. 5 |
| L. gasseri BNR17, 2013, Korea | 57 adults with a BMI of 23 or more | 12 weeks, with no change to diet or activity | Waist and hip shrank more than with placebo | Body weight did not differ significantly from placebo | Jung et al. 9 |
| L. gasseri BNR17, 2018, Korea | 90 adults with a BMI of 25 to 35 | 1 billion or 10 billion CFU a day, 12 weeks | Visceral fat area 21.6 cm2 smaller than placebo at the higher dose; waist smaller than at the start at both doses | Blood measures did not differ between groups; the abstract gives no weight result | Kim et al. 10 |
| Lactobacillus rhamnosus CGMCC1.3724 (now Lacticaseibacillus rhamnosus) | 125 adults aged 18 to 55, all with a BMI in the 30-plus range | 324 million CFU a day for 24 weeks, with a reduced diet for the first 12 | The 77 women lost 1.8 kg more than placebo by week 12 and 2.6 kg more by week 24 | In the whole group, no significant effect on weight loss | NIH ODS 3 |
Sources 3, 5 and 8 to 10, linked below. Visceral fat is fat inside the belly, around the organs. The two SBT2055 trials were run by researchers at a dairy company, and the 2018 BNR17 trial lists a contract research company among its affiliations; no company is named here.
The 2010 and 2013 abstracts report the SBT2055 changes against each group's own starting point, and NIH's Office of Dietary Supplements describes the 2013 results as significant compared with the control group.8,5,3 A result belongs to the strain and the food it came in: these trials tested two L. gasseri strains, one of them in fermented milk, and say nothing about other strains of the species.
Why do probiotic weight-loss studies disagree?
Because the strain, dose, length and people differ from trial to trial. In the reading of NIH's Office of Dietary Supplements, what probiotics do to body weight might depend on the strain, dose and duration, and on the user's age, sex and baseline body weight. Most trials ran 3 to 12 weeks, and many tested probiotics alongside diet or exercise changes.3,1,11
A Cleveland Clinic article makes that last point plainly: it is rare for scientists to study probiotics and weight loss in isolation, and because most studies include diet and exercise too, it is hard to know what results, if any, the probiotic can take credit for. Registered dietitian and microbiome researcher Gail Cresci, PhD, RD, LD, compares a probiotic with the trillions of microbes in a stool transplant: "With a probiotic, it's likely a person could only receive a fraction of that, from one to just a few beneficial microbes," and she sees no assurance that a probiotic supplement will affect weight loss.11
"However, these effects were small and of questionable clinical significance."
NIH Office of Dietary Supplements, on the 2018 meta-analysis
Results also move with single studies. In the 2026 meta-analysis, the BMI effect weakened to borderline significance, and the body fat effect lost significance, when one trial with uneven groups at the start was left out; the authors called their findings preliminary.7 And the 2017 review's split, with 2 of its 14 trials showing weight gain, is why its authors call the benefit strain dependent.4
What do diet and activity guidelines say about weight loss?
That lifestyle comes first. NIH's Office of Dietary Supplements says health experts agree that following a healthy dietary pattern, eating less and being physically active are the basis for long-term weight loss. CDC lists healthy eating patterns, regular physical activity, enough sleep and stress management, and says people who lose about 1 to 2 pounds a week are more likely to keep the weight off than people who lose it quicker.3,6
For activity, CDC says adults need at least 150 minutes of moderate-intensity physical activity a week, such as 30 minutes a day, 5 days a week, plus 2 days of muscle-strengthening activity.12 Its first steps for weight loss are writing down your reasons, tracking what you eat, drink, move and sleep for a few days, and setting two or three specific goals at a time, such as a 15-minute evening walk.6
The gut side of steady eating habits is in our 30-day gut habits checklist, and how quickly gut bacteria shift when eating changes is in how to reset your gut.
Are probiotics safe to take during weight loss?
For healthy people, mostly yes, with mild gut effects. NIH's Office of Dietary Supplements says common Lactobacillus and Bifidobacterium species are unlikely to cause harm, that the usual side effects are mild, self-limited gut symptoms like gas, and that rare serious infections have mainly involved people who were severely ill or immunocompromised. It advises talking with a health care provider before using any weight-loss supplement.3
Few people do. According to a large national survey the same fact sheet cites, less than one-third of US adults who use weight-loss dietary supplements discuss that use with a health care professional.3
Where Physician's Choice fits
Physician's Choice, a maker of gut health supplements, publishes this site. This read names no product; it reports what the trials and reviews measured, strain by strain.
The short version
Probiotics have not shown much effect on body weight: pooled trials put the difference at about half a kilogram, some reviews found none, and NIH calls the results inconsistent. A few Lactobacillus gasseri trials found modest drops in visceral fat that weakened after people stopped. Eating patterns, activity, sleep and stress management are what the guidelines name.
Notes on this page
- Where the question came from
- Of 1,145 public Reddit posts we read (250 communities, Sep 12 to Oct 12, 2026), none mentioned probiotics and weight in the same post. None is quoted here.
- What engines were asked
- Do probiotics help with weight loss, on Oct 22, 2026.
- What was left out
- Brand names, products, the companies behind each strain, trial results tied to a named condition, and any promise of a result.
- Sources
- 12 sources, each opened on Oct 22, 2026.
- Products
- None. This site names no product.
- Checks
- Last checked Oct 22, 2026. Each later check is dated here.
Weight loss questions
Can probiotics help you lose weight?
Not by much, in the trials so far. A 2018 meta-analysis of 15 trials found 0.60 kg more weight loss than placebo over 3 to 12 weeks, which NIH calls small and of questionable clinical significance, and a 2019 review of 19 trials found no difference in weight or BMI.
What is the best probiotic for weight loss?
No guideline or review we read names one. Results depend on the strain: of 14 Lactobacillus trials in a 2017 review, 9 found lower weight or body fat, 3 no effect and 2 weight gain. The most-cited strain, L. gasseri SBT2055, lowered visceral fat area in two 12-week trials of fermented milk.
How long do probiotics take to affect weight?
Most trials ran 3 to 12 weeks, and one 24-week trial NIH describes found no significant effect on weight in its whole group. In a 2013 L. gasseri trial, visceral fat fell over 12 weeks and the change weakened within 4 weeks of stopping, which the authors said suggests constant use might be needed.
Do probiotics reduce body fat?
Slightly, in some analyses. The 2018 meta-analysis found body fat percentage 0.60 points lower than placebo but no significant change in fat mass in kilograms, and in a 2026 meta-analysis a small body fat effect lost significance when one trial was left out. NIH calls the effects on body fat inconsistent.
Can probiotics cause weight gain?
In a few trials, yes. A 2017 review of 14 Lactobacillus trials found weight gain in 2, and a meta-analysis NIH cites found an average gain of 0.20 kg in children against an average loss of 0.54 kg in adults. The reviewers say the effect depends on the strain.
More reads
- Do probiotics work? A research note on what studies show
What the probiotic trials found overall.
- How to reset your gut: what studies show about how fast gut bacteria change
How fast gut bacteria shift with food.
- A 30-day gut habits checklist: fiber, fluids, meals and sleep
The daily habits, one source each.
- What is kefir? The cultures in it, how much a day, and kefir vs a probiotic
A fermented milk, culture by culture.
- Gut health supplements doctors recommend: what the guidelines actually say
What guidelines name, and what they do not.
- High-fiber foods for gut health: grams of fiber per serving
Fiber, food by food.
- Signs of an unhealthy gut: what is common, and what needs a doctor
Which signs need a doctor.
- Is yogurt a probiotic? Live cultures, labels and yogurt types compared
Live cultures in the dairy case.
- Digestive enzymes vs probiotics: what each can and cannot change
Two different things, side by side.
- Fermented foods vs probiotic supplements: what each one gives your gut
Live cultures in food, and the Stanford trial.
- Is bone broth good for gut health? What the evidence shows
A popular gut claim, checked.
- What helps bloating fast, naturally? Habits first, then the supplements with evidence
When bloating is the problem today.
Sources
- Borgeraas H, Johnson LK, Skattebu J, Hertel JK, Hjelmesaeth J. Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2018;19(2):219-232. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Suzumura EA, Bersch-Ferreira ÂC, Torreglosa CR, et al. Effects of oral supplementation with probiotics or synbiotics in overweight and obese adults: a systematic review and meta-analyses of randomized trials. Nutr Rev. 2019;77(6):430-450. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- NIH Office of Dietary Supplements. Dietary supplements for weight loss: fact sheet for health professionals. ods.od.nih.gov. Opened Oct 22, 2026 through a text reader (direct fetch blocked).
- Crovesy L, Ostrowski M, Ferreira DMTP, Rosado EL, Soares-Mota M. Effect of Lactobacillus on body weight and body fat in overweight subjects: a systematic review of randomized controlled clinical trials. Int J Obes (Lond). 2017;41(11):1607-1614. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Kadooka Y, Sato M, Ogawa A, et al. Effect of Lactobacillus gasseri SBT2055 in fermented milk on abdominal adiposity in adults in a randomised controlled trial. Br J Nutr. 2013;110(9):1696-703. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- CDC. Steps for losing weight. Last reviewed January 17, 2025. cdc.gov. Opened Oct 22, 2026 in a headless browser.
- Ko J, Chun J, Yoo C, Gonzalez DE, Lee Y. Effects of probiotics and synbiotics on body weight management in individuals with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Phys Act Nutr. 2026;30(2):78-89. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Kadooka Y, Sato M, Imaizumi K, et al. Regulation of abdominal adiposity by probiotics (Lactobacillus gasseri SBT2055) in adults with obese tendencies in a randomized controlled trial. Eur J Clin Nutr. 2010;64(6):636-43. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Jung SP, Lee KM, Kang JH, et al. Effect of Lactobacillus gasseri BNR17 on overweight and obese adults: a randomized, double-blind clinical trial. Korean J Fam Med. 2013;34(2):80-9. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Kim J, Yun JM, Kim MK, Kwon O, Cho B. Lactobacillus gasseri BNR17 supplementation reduces the visceral fat accumulation and waist circumference in obese adults: a randomized, double-blind, placebo-controlled trial. J Med Food. 2018;21(5):454-461. pubmed.ncbi.nlm.nih.gov. Abstract read Oct 22, 2026.
- Cleveland Clinic. How probiotics support healthy weight loss. Health Essentials, with registered dietitian Gail Cresci, PhD, RD, LD. January 23, 2025. health.clevelandclinic.org. Opened Oct 22, 2026.
- CDC. Adult activity: an overview. December 20, 2023. cdc.gov. Opened Oct 22, 2026 in a headless browser.