The link between the gut microbiome and obesity seems clear, but just how changes to gut bacteria can cause weight gain is not. A University of Iowa study in mice shows that drug-induced changes to the gut microbiome can cause obesity by reducing the resting metabolic rate—the rate at which calories are burned while sleeping or resting. The findings, published in the journal eBiomedicine, highlight the critical role of gut microbes in energy balance and suggest that unhealthy microbiome shifts can lead to weight gain and obesity by altering resting metabolism. Dr. John Kirby, professor of microbiology and urology, teamed up with Dr. Justin Grobe, assistant professor of pharmacology, to find out how this risperidone-induced microbiome shift causes weight gain. The UI research team also included first author Sarah Bahr, Benjamin Weidemann, Ana Castro, John Walsh, Orlando deLeon, Colin Burnett, Nicole Pearson, and Daryl Murry.