With probiotics and prebiotics all the rage, bacteria have never seen better days. Hundreds of supplements seem to fight for space on store shelves, while mini kombucha shops, purporting the benefits of symbiotic colonies of bacteria and yeast, are popping up all over the country.
But as spring arrives and many Americans aim to shed a few pounds as they shed clothing, you may wonder how probiotics affect weight – if at all – as an increased number of products promise slimming effects.
In 2012, a study published in the Indian Journal of Endocrinology and Metabolism found a relationship between diet, gut microbiota and metabolic syndrome. “Unraveled mechanisms of probiotic and prebiotics action provided [sic] strong scientific base for developing dietary intervention strategies,” wrote the authors. “However, more in-depth studies related to their efficacy and effectiveness are required to be carried in human subjects to make these therapies more competitive in [sic] global functional food market.”
Two years later, the British Journal of Nutrition reported that certain probiotics might help women lose weight. In a double-blind, placebo-controlled trial involving obese participants, women who had taken supplements with Lactobacillus rhamnosus CGMCC1.3724 (LPR) saw a “significantly higher” weight loss than those in the placebo group. Participants took the supplements while restricting their calorie intake for the first 12 weeks followed by 12 weeks of weight maintenance, leading researchers to conclude that particular strain of Lactobacillus rhamnosus “helps obese women to achieve sustainable weight loss.”
But not so fast, says Ian Orme, PhD, a professor of microbiology, immunology and pathology at Colorado State University. “I haven’t seen any evidence that probiotics can promote weight loss,” he says. “What would be the mechanism of taking a probiotic that would promote weight loss? My personal opinion is that probiotics do very little.”
Registered dietitian Tanya Zuckerbrot, a best-selling author and the creator of the diet and lifestyle program F-Factor, shares this perspective. “According to the current research on probiotics and weight loss, there’s not enough strong clinical evidence to support the efficacy of probiotics and decreased body fat and body mass index,” she says. “More research needs to be done to conclude otherwise.”
However, Zuckerbrot does see interest in a 2012 review published in the Journal of Clinical Gastroenterology showing that obese individuals have a higher proportion of the bacterial phyla Firmicutes to Bacteroidetes compared to lean individuals who have the inverse. Could promoting more Bacteroidetes in the gut prevent weight gain? Perhaps, she says, though more research is necessary in this area as well.
According to Zuckerbrot, the best hope for weight management resides in prebiotics. She says this is simply because of their composition. “Prebiotics are nondigestible high-fiber compounds found in foods such as Jerusalem artichokes and onions,” she says. “A high-fiber diet is linked to lower body weight and decreased risk for obesity.” Because high-fiber foods keep you feeling fuller longer, you generally eat less throughout the day, which can lead to weight loss. “Once prebiotics reach the colon, they provide nutrients to the healthy bacteria in the gut, the probiotics,” says Zuckerbrot. “Prebiotics and probiotics work together to improve digestion, decrease risk of chronic disease and enhance immune function.”