The microbes in our gut impact our health through a variety of mechanisms. These mechanisms include direct impacts on our metabolism and the metabolites circulating in our bloodstream. A team of researchers recently set out to better understand how our gut microbes might influence the development of diet- induced obesity. First, they examined the gut microbiomes of 99 Korean individuals. People with obesity-related indicators, including increased visceral fat tissue and fatty liver, had reduced levels of two Bifidobacterium species. Specifically, Bifidobacterium longum and Bifidobacterium bifidum. The researchers hypothesized that these bacteria could be protective against diet-induced obesity and moved to experiments in mice. There they found that only specific strains of these Bifidobacterium species could protect against diet-induced obesity, and the protective strains had more gene expression related to carbohydrate or nucleoside metabolic processes than other strains. Feeding the mice commercially available B. longum and B. bifidum probiotics led to changes in bile acid signaling. This altered their adipose tissue metabolism in ways that protected them from diet-induced obesity and fatty liver disease while improving their glucose balance. Overall, these results suggest that screening gut microbes for protective bacterial strains like these could lead to new therapeutic strategies for metabolic disease.