If you’re one of those people who puts on weight while another person eating the same meal doesn’t, blame your gut! Greg Caporaso says it’s all about the microbiome — or the microbes living in our bodies — that determines how many calories we extract from food and also, how susceptible we are to disease.

“The rate of change over the microbiome may be predictive of whether an individual might be prone to getting a Clostridium difficile, or a C. diff, infection, or whether a particular microbiome-based treatment might be successful or not successful for a certain individual,” Caporaso says.

Caporaso is an assistant professor in Northern Arizona University’s Department of Biological Sciences. He recently conducted a study involving 85 college students. It revealed for the first time just how much the bacterial makeup varies between individuals, and how often it changes.

The study also showed the differing microbiomes between parts of the body like the tongue, forehead, stomach or the palms of our hands. And, he says, this can fluctuate based on factors like diet, exercise and environment.

“If you’re working on a farm, you may have different microbes on your hands on a day-to-day basis than if you’re sitting in an office all day. They do things like assist with the digestion of foods, they are involved early in life in training the immune system, and so being a healthy human, in part, means having healthy microbial communities in and on your body,” Caporaso says.

Caporaso hopes his research will help doctors determine personalized treatment for their sick patients, all based on their microbiomes. Or in other words, what kinds of bugs are living in and on them that help them get well.