Turns out our gut bugs may be creating oversized guts. That’s one of the suggestions given as to why some suffer from obesity while others don’t. Airing Thursday under CBC’s The Nature of Things banner, “It Takes Guts” posits the 100 trillion microbes living in our digestive system influence obesity in some.

The story begins with Adrianna, who has always battled her weight. Tired of being “the fat girl,” she started an exercise regimen in her 20s and cut fast food from her diet. She didn’t lose any weight. That’s because, according to obesity expert Dr. Arya Sharma of the University of Alberta, some bodies are predisposed to being that way thanks to the microbes inside them.

Geneticist Professor Tim Spector is up next, explaining microbes influence how we eat, what we eat, how we get energy from our food, protect our immune system, help us harvest calories and produce key vitamins and nutrients. These super-small spirals, blobs and other shapes are integral in our lives, and aren’t all bad.

“It Takes Guts” offers a lot of information in an interesting way, mixing expert interviews with colourful graphics while explaining how eating processed foods is like dropping a nuclear bomb on microbes—courtesy of Spector’s son, Tom—and what we can do to cultivate and enrich the critters in our gut on the path to better health. And that artificial poop machine at the University of Guelph? Make sure you tune in for that.

The Nature of Things airs Thursdays at 8 p.m. on CBC.