Many people worry about the outside of their gut – watching their weight and suffering through sit-ups in search of six-pack abs.

Research from UC San Francisco is showing that we also should pay attention to what's inside the gut.

Gut bacteria may affect both our cravings and moods to get us to eat what they want, and often are driving us toward obesity, according to an article published this month in the journal BioEssays.

Researchers concluded from a review of recent scientific literature that microbes influence human eating behavior and dietary choices to favor consumption of the particular nutrients they grow best on, rather than simply passively living off whatever nutrients we choose to send their way.

“Bacteria within the gut are manipulative,” said corresponding author on the paper Carlo Maley, director of the Center for Evolution and Cancer with the Helen Diller Family Comprehensive Cancer Center at UCSF. “There is a diversity of interests represented in the microbiome, some aligned with our own dietary goals, and others not.”

We also can influence this diverse community of microbes, collectively known as the gut microbiome, by altering what we ingest, Maley said, with measurable changes in the microbiome within 24 hours of diet change.

“Our diets have a huge impact on microbial populations in the gut,” Maley said. “It's a whole ecosystem, and it's evolving on the time scale of minutes.”

The gut is a growing field for research.

Michael Fischbach, a UCSF assistant professor of bioengineering and therapeutic sciences, studies gut bacteria and how they could help reveal the causes and new treatments for Crohn's disease and obesity.

“When I look at a person, I don't just see a warm, shiny human being,” Fischbach said. “I see bacteria crawling all over you and living on every surface that's exposed and not exposed in your entire body. And you're lucky that they're there because these bacteria do very important things for you. They make your immune system function properly. They help you digest foods. And they produce important chemicals that serve as vitamins for your body.”

With advancements in genetic sequencing technology, Fischbach and colleagues are mining gut bacteria for natural products – small molecules from microbes – that could hold the key for treating diseases.

“You used to have to travel to the coast of Palau to mine the ocean sediment for drugs,” Fischbach said. “Now we can just check our gut!”

Fischbach discussed his gut research with collaborator Justin Sonnenburg, a Stanford University microbiologist with degrees from UC Davis and UC San Diego, at the recent New York Times Health for Tomorrow conference at UCSF Mission Bay Conference Center.

“The beauty of being in basic research is you don't know where you're going to end up,” Fischbach said after their panel presentation. “It's nice to be on a journey where you don't know where the ship lands. I hope it's going to improve human health.”

Read more:
-Do gut bacteria rule our minds?, UCSF
-Our microbiome may be looking out for itself, New York Times
-The next frontier of medicine, Slate
-Culturing for cures, UCSF