A Healthy Gut Burns More Calories During Sleep

An unhealthy shift in your gut microbes might cause you to gain weight by changing how many calories you burn while you sleep, a new study with mice suggests.

When researchers used a drug to change the gut microbiome in mice, they saw a reduction in resting metabolic rate—the rate at which calories are burned while sleeping or resting.

“Our research leads to the conclusion that it is probably bacteria (in the gut) that are responsible for the calories you burn while you are asleep,” says John Kirby, professor of microbiology and urology at the University of Iowa Carver College of Medicine and one of the authors of the study in eBiomedicine.


Kirby and his colleagues focused on the effects of risperidone, an antipsychotic drug that causes significant weight gain in patients. Risperidone is used to treat various psychiatric disorders in adults and children, including autism, bipolar disorder, and schizophrenia, and prescribing rates for children have increased nearly eight-fold over the last two decades.

In an earlier study, Kirby and Chadi Calarge, a University of Iowa pediatric psychiatrist, compared patients taking risperidone long-term to patients who were not on the drug. They found that weight gain was correlated with a significant shift in the composition of the patients’ gut microbiomes. These results were published in Translational Psychiatry.

In the new study, Kirby teamed up with Justin Grobe, assistant professor of pharmacology, to find out how this risperidone-induced microbiome shift causes weight gain. Mirroring the human studies, the researchers showed that risperidone causes weight gain in mice (an extra 2.5 grams, or approximately 10 percent of the total body mass, over two months, compared to controls) and significantly alters the bacterial composition of the mouse microbiome.

They then showed that the altered microbiome causes a reduction in resting metabolic rate that is entirely responsible for the excess weight gain.

“The control mice gain a little weight as they age and their microbiome undergoes a ‘healthy shift’ due to aging. With the risperidone, the mice become obese and exhibit an alternative, less healthy shift in their microbiome,” Kirby says. “With this study, we now have a mechanism for how a shift in the microbiome contributes to weight gain, and it’s to do with changes to the resting metabolic rate.”

In fact, the scientists found that the amount of weight gain was pretty alarming, continue to the next page to see what their research uncovered.