Comparative meta-analysis of the effect of Lactobacillus species on weight gain in humans and animals

Obesity is associated with alteration of the gut microbiota. In order to clarify the effect of Lactobacillus-containing probiotics (LCP) on weight we performed a meta-analysis of clinical studies and experimental models. We intended to assess effects by Lactobacillus species. A broad search with no date or language restriction was performed. We included randomized controlled trials (RCTs) and comparative clinical studies in humans and animals or experimental models assessing the effect of Lactobacillus-containing probiotics on weight. We primarily attempted to extract and use change from baseline values. Data were extracted independently by two authors. Results were pooled by host and by Lactobacillus species and are summarized in a meta-analysis of standardized difference in means (SMDs). We identified and included 17 RCTs in humans, 51 studies on farm animals and 14 experimental models. Lactobacillus acidophilus administration resulted in significant weight gain in humans and in animals (SMD 0.15; 95% confidence intervals 0.05–0.25). Results were consistent in humans and animals. Lactobacillus fermentum and Lactobacillus ingluviei were associated with weight gain in animals. Lactobacillus plantarum was associated with weight loss in animals and Lactobacillus gasseri was associated with weight loss both in obese humans and in animals. Different Lactobacillus species are associated different effects on weight change that are host-specific. Further studies are needed to clarify the role of Lactobacillus species in the human energy harvest and weight regulation. Attention should be drawn to the potential effects of commonly marketed lactobacillus-containing probiotics on weight gain.