Yes, but only one strain, only modestly, and only while you keep taking it. In two randomized, placebo-controlled trials, fermented milk containing Lactobacillus gasseri SBT2055 cut visceral (belly) fat by 4.6% over 12 weeks in the first trial and by about 8–9% in the second 12. When people stopped for four weeks, the effect faded 2. A product that just says "L. gasseri" on the label is not the strain that was tested.
That makes SBT2055 one of the few probiotics with a real, repeated human result on body fat, and also a good example of why probiotic marketing runs ahead of the data. Here is what each trial found, the dose behind it, and how to tell whether a product actually contains it.
The two SBT2055 trials
| 2010 trial | 2013 trial | |
|---|---|---|
| People | 87 adults, higher BMI and belly fat | 210 adults, large visceral fat area |
| Daily SBT2055 | About 20 billion CFU in fermented milk | About 2 billion or 200 million CFU |
| Length | 12 weeks | 12 weeks, then 4 weeks off |
| Visceral fat | −4.6% | −8.5% and −8.2% |
| Other changes | Weight −1.4%, waist −1.8% | BMI, waist, hip and body fat down |
| After stopping | Not reported | Effect attenuated within 4 weeks |
Does Lactobacillus gasseri reduce belly fat?
The specific strain SBT2055 (also written LG2055) does, in the trials that tested it. Both were run by the same Japanese research group, both used CT scans to measure abdominal fat directly, and both compared fermented milk with the strain against the same fermented milk without it.
- The 2010 trial enrolled 87 adults with a higher BMI and more abdominal fat. After 12 weeks of 200 g a day of fermented milk with SBT2055, visceral fat fell by an average of 4.6% and subcutaneous belly fat by 3.3%. Body weight dropped 1.4% (about 1.1 kg), and waist size 1.8% (about 1.7 cm). None of these fell significantly in the control group 1.
- The 2013 trial enrolled 210 adults with large visceral fat areas and tested two lower doses. Visceral fat fell by 8.5% and 8.2% from baseline in the two SBT2055 groups at week 12, with smaller BMI, waist, hip and body-fat measurements too. Again, the control group showed no significant decrease 2.
Two trials pointing the same way, with imaging endpoints, is better evidence than most "belly fat" probiotics have. It still adds up to a modest effect: about a kilogram of weight and a couple of centimeters of waist, nowhere near what a GLP-1 medication does.
Does the belly fat come back when you stop?
Yes. In the 2013 trial, participants stopped drinking the fermented milk for four weeks after the 12-week treatment, and that pause "attenuated" the reductions. The authors concluded that "constant consumption might be needed to maintain the effect" 2.
This is the most important practical point on this page. SBT2055 doesn't reset anything. Whatever it does lasts about as long as you keep taking it, so it's a daily habit, not a course.
How much L. gasseri SBT2055 was used in the studies?
Both trials delivered the strain in 200 g a day of fermented milk, a bit less than a typical cup of yogurt:
- 2010: fermented milk with 10⁸ CFU of SBT2055 per gram, so about 20 billion CFU a day 1.
- 2013: 10⁷ or 10⁶ CFU per gram, so about 2 billion or 200 million CFU a day. Both doses worked about equally well over 12 weeks 2.
So the effective dose in these trials was in the hundreds of millions to billions of CFU a day, and always in fermented milk. Capsule products haven't been tested in comparable trials, so whether a capsule works the same way is unproven.
Evidence summary
- Visceral fat reduction (4.6% and ~8–9%, on-treatment)Moderate evidence
Two randomized controlled trials with CT-measured endpoints (Kadooka 2010, 2013).
- Durability after stopping the strainNo evidence
Stopping for 4 weeks attenuated the reductions in the 2013 trial; the authors concluded constant intake may be needed.
- Reduced dietary-fat absorptionWeak evidence
Increased fecal fat excretion in a human study plus in vitro fat-emulsion data.
- Anti-inflammatory / insulin effectsWeak evidence
Mostly mouse and rat data — adipose inflammation, gut permeability, insulin secretion.
How to read an L. gasseri product label
Probiotic effects belong to specific strains, and a result for one strain doesn't transfer to the species as a whole. Before buying anything sold for belly fat, check three things:
- The strain code. Look for "SBT2055" (or "LG2055") after Lactobacillus gasseri. If the label just says "L. gasseri" or "Lactobacillus gasseri blend," you're not buying the studied strain.
- The count. The trials used roughly 200 million to 20 billion CFU a day. A label that gives a total for a blend without a per-strain count can't tell you how much SBT2055 you're getting.
- The form. Both trials used fermented milk. A capsule may or may not behave the same way.
Most "women's" probiotics that mention belly fat don't contain SBT2055 at all. Our best probiotics for women page shows which strains actually appear in the products we list, and our best probiotics for weight loss page rates weight-loss products strain by strain.
How does SBT2055 work?
The best human evidence points to fat absorption. In a study in healthy Japanese adults, SBT2055 increased the amount of fat excreted in stool, and lab work showed it made fat droplets larger, which slows how quickly fat is broken down and absorbed 3. That's a plausible, partly human explanation for a small drop in body fat.
The rest of the mechanism story comes from animals. In mice on a high-fat diet, SBT2055 reduced inflammatory immune cells in fat tissue 4 and reduced fat-tissue inflammation and gut permeability 5. In a diabetic rat model it improved insulin secretion 6. These findings are coherent, but animal metabolic results often don't carry over to people, so treat them as hypotheses. For why gut permeability matters metabolically, see leaky gut and metabolism, and for the insulin side, the microbiome and insulin resistance.
Key takeaway
What SBT2055 can and can't do
- Two RCTs show a real but modest visceral-fat drop (4.6% and about 8–9%) over 12 weeks.
- The effect reversed within weeks of stopping — benefit depends on continuous daily intake.
- It's strain-specific: 'L. gasseri' on a label isn't the same as the studied SBT2055 strain at the studied dose.
- Treat it as one supporting lever inside a fiber-rich diet — not a replacement for diet, and nothing like a GLP-1 medication.
Does any L. gasseri work, or only SBT2055?
Only SBT2055 has this evidence. The broader picture for probiotics and weight is much weaker: a meta-analysis of randomized trials found that probiotics as a group reduced body weight by only about 0.6 kg versus placebo, because it pools many different strains and products, most of which weren't SBT2055 7. We walk through that pooled result in do probiotics help weight and metabolism?.
If you want a probiotic for metabolic reasons rather than belly fat specifically, our best metabolic probiotic comparison lines up the options by strain, dose and price.
Is Lactobacillus gasseri safe?
For most healthy adults, L. gasseri is well tolerated, and it's a species commonly found in fermented dairy. The general probiotic caution still applies: rare bloodstream infections have been documented in people who are immunocompromised or critically ill, so anyone with a serious medical condition should check with a clinician first 8.
The bottom line
Lactobacillus gasseri SBT2055 is one of the few probiotics with randomized human evidence for reducing belly fat: about 4.6% of visceral fat in one 12-week trial and about 8–9% in a second. The effect is modest, specific to that strain in fermented milk, and it faded within four weeks of stopping. If you try it, buy a product that names SBT2055, expect a small change rather than a transformation, and keep the bigger levers in view: a fiber-rich diet, activity, and, where appropriate, medication. For the system-level picture, start with the gut–metabolism connection.