Research review
Does acidophilus help with weight loss? What the research does and doesn't show
The evidence doesn't support acidophilus as a weight-loss aid. A systematic review of Lactobacillus and body weight found mixed, strain-dependent results, and the one placebo-controlled trial to test a blend containing acidophilus against body composition specifically found no significant difference.
The evidence doesn't support acidophilus, alone or in a blend, as something that produces weight loss. A systematic review of Lactobacillus and body weight found mixed, strain-dependent results across 14 trials, and the one placebo-controlled trial to test a blend containing acidophilus against actual body composition found no significant difference from placebo.
What the evidence doesn't support
It doesn't support Lactobacillus acidophilus as a weight-loss supplement, and it doesn't support the idea that "probiotics for weight loss" is a settled, positive finding — the research on Lactobacillus and body weight is a mix of positive, null and even negative results, and no trial has isolated a single named acidophilus strain to test it alone against body weight or fat. It also doesn't support treating a result from a different Lactobacillus species or strain as something acidophilus would also do; probiotic effects are strain-specific, and a genomic analysis of sequenced Lactobacillus strains found that closely related strains can differ enough genetically that a result for one doesn't carry over to another.
What the trials found
A systematic review searched for every randomized controlled trial testing Lactobacillus supplementation against body weight or fat mass in overweight adults and found 14 that qualified. Of those, 9 reported decreased body weight and/or fat, 3 found no effect, and 2 found weight gain. The review's stated conclusion was that the effects are strain-dependent: several specific strains and combinations were associated with a decrease, including L. acidophilus, but only ever combined with other strains — L. acidophilus and L. casei together with phenolic compounds, for example — never tested as a single ingredient on its own. Other combinations in the same review showed no benefit or an increase in weight.
A separate placebo-controlled trial gave 20 adults following a low-carbohydrate, high-protein weight-loss diet a daily synbiotic supplement — L. acidophilus, Bifidobacterium lactis, B. longum and B. bifidum, plus a prebiotic fiber — or placebo, for 3 months. At the end of the trial, there was no statistically significant difference between the groups in body mass, BMI, body fat mass, body fat percentage, lean mass or bone mineral content. The supplement did increase the amount of Lactobacillus and Bifidobacterium detected in stool, and appeared to increase overall gut microbiota richness — a change in gut bacteria composition, without a matching change in body weight or fat in this trial.
Read together, the picture is a mixed, strain-dependent literature where L. acidophilus has never been isolated and tested alone, and the one trial that measured body composition directly, in a blend that included acidophilus, found no effect.
Questions people ask
Can acidophilus help with weight loss?
No trial has tested a named acidophilus strain alone against weight loss. The closest available evidence — a blend including acidophilus, tested against actual body composition — found no significant difference from placebo.
Will acidophilus help with weight loss if I'm also dieting?
The one trial that tested a probiotic blend including acidophilus alongside a weight-loss diet found no additional effect on body weight or fat compared with the diet plus placebo.
What probiotic is best for weight loss?
This page doesn't rank strains for weight loss. The systematic review above found effects to be strain-dependent and mixed across the Lactobacillus species generally, with no single strain established as reliably effective.
When to talk to a doctor
Weight management that involves a medical condition, or a specific health goal, is worth discussing with a doctor or registered dietitian, who can look at diet, activity and any underlying conditions together. Acidophilus is not a treatment for obesity, and nothing in the evidence above supports using it as a weight-loss strategy on its own.
Related reading: acidophilus: what the research shows and acidophilus benefits: what the research does and doesn't show.
Sources
- Effect of Lactobacillus on body weight and body fat in overweight subjects: a systematic review of randomized controlled clinical trials A systematic review of 14 trials found Lactobacillus's effect on body weight in overweight adults is mixed and strain-dependent — most trials found a decrease, some found none, and two found weight gain; L. acidophilus appeared only in multi-ingredient combinations, never tested alone.
- Effects of Synbiotic Supplement on Human Gut Microbiota, Body Composition and Weight Loss in Obesity A 3-month placebo-controlled trial of a four-species probiotic blend that included L. acidophilus, plus a prebiotic fiber, found no significant difference in body weight, BMI, body fat or lean mass compared with placebo, in adults on a weight-loss diet — a null result for body composition.
- Functional genomics of probiotic Lactobacilli Closely related Lactobacillus strains differ enough genetically that a finding for one named strain can't be assumed to apply to a different strain, even within the same species.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.