Do probiotics help with weight loss? What the research does and doesn't show

The evidence does not support probiotics as a way to lose a meaningful amount of weight. Pooled trials found small average differences: a mean body-weight difference of -0.52 across 12 trials, and 0.6 kg versus placebo across 15. Larger effects were for single strains at 10 billion CFU a day or more.

What the evidence doesn't support

• Probiotics as a weight-loss aid. The average difference was under one kilogram in trials lasting weeks to months.
• Any probiotic working. The reviews say effects depend on strain, dose and duration, and the larger effects were in single-strain, high-dose regimens, some of which also included health guidance.
• Better cholesterol. The 2026 review found no significant effect on total cholesterol or triglycerides.
• A fixed time of day. We found no trial that tested when to take a probiotic for weight.

What the trials found

2026 meta-analysis: 12 trials

In overweight and obese adults, probiotics lowered body weight (mean difference -0.52), BMI (-0.22), waist circumference (-0.29) and body fat percentage (-0.59) versus control. Total cholesterol and triglycerides did not change significantly. Single-strain regimens at 10 billion CFU a day or more, or combined with health guidance, showed larger effects in simple obesity. The effect is small and the strains varied.

2018 meta-analysis: 15 trials, 957 people

Over 3 to 12 weeks in people with overweight or obesity (mean BMI 27.6), probiotics lowered body weight by 0.60 kg more than placebo (95% CI -1.19 to -0.01), BMI by 0.27 and fat percentage by 0.60 percentage points. The change in fat mass was not significant. The authors said the effect sizes were small.

2025 meta-analysis: 8 trials, 412 people with obesity

Probiotics were associated with greater weight loss, waist and visceral fat reduction versus control, with no significant difference in BMI or LDL cholesterol. The abstract gives p-values rather than effect sizes, and the trials were small.

Questions people ask

Will probiotics help you lose weight? Can probiotics make you lose weight?

On average the trials found a small difference (a mean body-weight difference of -0.52 in the newest review) in people already above a healthy weight. That is not the result most searchers want. A probiotic is not a weight-loss treatment.

What probiotics are best for weight loss, and which strains help?

The review points to single strains at 10 billion CFU a day or more, but does not name a strain that works. Effects were strain-specific, so a mixture of species on a label does not inherit them. See how to choose a good probiotic.

When should you take probiotics for weight loss?

No trial we verified tested timing for weight. The general timing question is covered in best time to take probiotics.

How do probiotics help with weight loss?

The mechanism is not established by these trials; they measured weight and body composition, not how any change happened.

Do probiotics cause weight gain?

The pooled trials in overweight adults found small reductions, not gains. We did not verify a trial in underweight people, so no claim is made there. See probiotics side effects.

When to talk to a doctor

A supplement is not a treatment for obesity. If you want to change your weight, or have unexplained weight gain or loss, a doctor can assess causes and options. Ask a doctor or pharmacist before starting a probiotic if you have a weakened immune system, are pregnant or nursing, or take prescription medicine. Related: probiotics benefits.