The microbiome of hibernating bears may hold the key to combating obesity.

Brown bears hibernate for up to six months each year. Prior to hibernation, bears double their fat stores, becoming “seasonally obese.” Displaying a cunning bit of reasoning, researchers from the University of Gothenburg in Sweden have now shown that the secret to healthy weight gain may lie in the bears’ gut microbiome, which also varies seasonally. Their findings were published last week (February 4) in Cell Reports.

Knowing that the gut microbiome is very responsive to what we eat, the group hypothesized that if a bear eats a lot in the summer and doesn’t eat in the winter, then there should be an alteration in the gut microbiome.

Does a bear s#*t in the woods…?

If it does, there’s an eager scientist waiting to take a sample! 

The research team collected microbiome samples (in the form of feces), from wild brown bears in February when they were hibernating (how does someone get poop from a sleeping bear?!), and in June when the bears were active. They then put microbiome samples form each season into germ-free mice. This simple strategy allowed them to investigate effects specific to the microbiome samples.

What they found, was that if a mouse received a bears' summer microbiome, it gained more fat compared to a mouse colonized with the microbiome of the same bear in the winter. Interestingly, even though the mice gained more fat mass, their glucose tolerance (an indicator of diabetes), wasn’t impaired.

The study is interesting because it suggests that gut microbes may actually be driving metabolism in way that could be harnessed, understanding the role of energy-harvesting microbes in summer samples could lead to potential therapeutics for people suffering from malnutrition