Sept. 17, 2021 -- If you have a gut feeling something is preventing you from losing as much weight as you would like to, you could be right.

Researchers found that the gut microbiome — the bacteria that help digest food and absorb nutrients in the intestines — can influence your ability to lose weight.

They identified genes within these bacteria that determine how quickly the bacteria grow, how well people can take advantage of nutrients in food, and whether starches and fiber, in particular, get broken down into sugars too quickly to aid weight loss.

"Some people have a harder time losing weight than others," study author Sean Gibbons, PhD, says. "For example, some people are able to control their weight through basic lifestyle interventions, while others may not."

Also, it is difficult to predict who will respond to changes in diet or exercise and who might require more intense strategies.

The study, which was published online Sept. 14 in mSystems, a journal of the American Society for Microbiology, could bring us closer to an answer.

"We've identified specific genetic signatures in the gut microbiome that were predictive of weight loss response in a small cohort of patients following a healthy lifestyle intervention," says Gibbons, assistant professor at the Institute for Systems Biology in Seattle.

Weight Loss Takes Guts?

Differences in 31 functional genes emerged from the gut microbiome among 48 people who lost 1% or more of their weight each month compared with 57 others whose weight remained the same. Researchers analyzed stool samples taken 6 to 12 months after people started a commercial weight loss coaching program.

The study aligns with previous research showing different types of bacteria in the gut microbiome can affect the success of weight loss interventions, but they took it a step further to determine how this works.

"We know that the gut microbiome plays an important role in weight management and can also influence a response to weight loss interventions. However, specific gut microbiome features that can explain this observation in more detail are still to be discovered," Hana Kahleova, MD, director of clinical research at the Physicians Committee for Responsible Medicine in Washington, DC, says..

Good vs Bad Players

On the plus side, genes that help bacteria grow more rapidly were associated with weight loss. These bacteria take more of the nutrients in food for themselves, leaving less to go toward human weight gain compared with slower-growing bacteria.

In fact, some prior evidence points to a particular gut bacteria, Prevotella, helping weight loss. "In our study," Gibbons says, "we found that some of the fastest-growing microbes in the weight-loss responder group were from the genus Prevotella."

On the other hand, bacteria that produce more enzymes to breakdown starches or fiber quickly into sugars, for example, were linked with making people more resistant to weight loss.

"By understanding these functional patterns, we may one day be able to engineer resistant microbiomes to be more permissive to weight loss," Gibbons said.

Kahleova agreed. "These findings expand our understanding on the specific features of the gut microbiome that play a role in weight loss," she said.

Fecal Microbiota Transplants?

What do the findings mean for people willing to adjust their diet — or undergo a fecal transplant — to include more of the gut bacteria that facilitate weight loss?

It could be too soon for such interventions, Gibbons said. "It is still very difficult to rationally engineer your gut microbiome."

"Interestingly, a recent study suggests that fecal transplants from a high-Prevotella donor may be able to flip low-Prevotella recipients to high-Prevotella," Gibbons said.

More research is required, however, to understand whether or not these fecal microbial transplant-flipped individuals are also more capable of weight loss, he added.

Beyond that, "I can't give any specific recommendations, other than that [people] should eat more fiber-rich, plant-based, whole foods and reduce their consumption of red meat. That's well-supported."

"Also, prepare your own meals, rather than relying on sugar and sodium-rich processed foods," Gibbons said.