Scan the internet and you’ll see products for, and articles about, use of probiotics to enhance weight loss. But are there any data suggesting that probiotics, prebiotics or synbiotics can help with weight loss? Before exploring this question, keep in mind that weight loss is not always a good thing. Infants and children need to gain weight and a few small studies have shown that probiotics can boost weight gain and improve growth parameters in undernourished children (Effects of probiotics on child growth: a systematic review). Also, weight loss due to loss of muscle mass is not desired. But let’s assume that the target is people who have excess fat to lose.
The approach of considering the totality of the evidence using the systematic review and meta-analysis process has been brought to bear on this topic. In 2015, Probiotics for weight loss: a systematic review and meta-analysis (Park & Bae. 2015) was published. Only 4 randomized, controlled trials that compared probiotics to placebo were found, and when the data from these 4 studies were pooled, no significant effect of probiotics on body weight or body mass index (BMI) was observed. Different strains were used in the included studies, and perhaps some strains are more effective than others.
In March 2018, another systematic review, which expanded inclusion criteria, was conducted. Dietary Alteration of the Gut Microbiome and Its Impact on Weight and Fat Mass: A Systematic Review and Meta-Analysis (John et al. 2018) included studies testing prebiotics and synbiotics (products that contain both probiotics and prebiotics) in addition to probiotics. In this review, 21 studies (with 33 study arms – 22 probiotic, 6 prebiotic, 5 synbiotic) were included.
Included study characteristics:
- Randomized and non-randomized trials included
- BMI >= 25 (overweight and obese)
- Adults only (18 or older)
- Studies with primary outcome measures of difference in mean change in BMI/body weight or fat mass, compared to placebo
- Participants were healthy or with diagnosed conditions (diabetes, non-alcoholic fatty liver disease, metabolic syndrome, post Roux-en-Y gastric bypass)
- No restrictions on probiotic intervention (strains, dose or delivery matrix). Several strains used (Pediococcus pentosaceus LP28; gasseri BNR17; L. gasseri SBT2055; L. casei Shirota; B. breve B-3; L. rhamnosus CGMCC1.3724; L. plantarum TENSIA; B. lactis 420; several with multi-strain combinations)
- Prebiotic interventions included FOS, GOS, inulin, polydextrose and yellow pea fiber
- Duration of intervention among included studies ranged from 15 days – 24 weeks
- Attrition bias – unequal loss of participants from the arms of the trials – was a problem for the included studies
Pooled together, these studies found that probiotic use was associated with decreased BMI, weight and fat mass; prebiotics reduced body weight; and synbiotics had no effect. But clearly, this is a heterogeneous group of studies. Considering the different modes of action of the included interventions, combining them into one meta-analysis needs to be justified. The authors group these interventions by considering them all dietary strategies that alter the gut microbiome, but this more hypothesis than established fact. The more useful contribution of this paper is that it undertook the systematic review process, which reveals the totality of the available data on probiotics, prebiotics and synbiotics on some indicators of weight loss. In short, this newly evolving field of investigation suggests that there may be value in these interventions. The data are starting to accumulate.
But there are many unanswered questions. More studies are needed to: understand the most effective interventions (probiotics, prebiotics or a combination of both) and dose; the importance of intervention duration, which subgroup analysis did not clarify; are benefits sustained with or without continued intervention; what is the role of diet and underlying medical conditions on outcomes.
Additional reading and related posts:
Probiotics and Weight Loss, 2017 Medscape article (log in required to view)
Microbiota manipulation for weight change. Dror et al. 2017