Scientists have identified a gut microbiome pathway that can push body fat toward burning more energy, at least in mice. In a new animal study published in Nature, researchers found that a low-protein diet triggered “beiging,” a process that shifts energy-storing white fat toward beige fat, which burns more calories for heat.
The key was not the diet alone. The effect depended on the presence of specific gut bacteria and on two linked biological signals involving bile acids and a liver hormone called FGF21. The work is mechanistic and early-stage, and it does not show that lowering protein intake would produce similar results in people.
“Fat tissue is not fixed — it’s surprisingly adaptable,” said Kenya Honda, M.D., Ph.D., a co-senior author and adjunct professor at City of Hope. “We found that certain gut bacteria can sense what the host is eating and translate that information into signals that tell fat cells to burn energy.”
Researchers compared mice that had a typical microbiome with germ-free mice that had none. Mice on a low-protein diet developed substantial beige fat only when the right microbes were present. When the same diet was given to germ-free mice, the fat-burning shift disappeared.
“This told us the diet alone wasn’t enough,” Honda said. “The gut microbiome was essential.”
The team then identified four bacterial strains that were needed for the effect. When introduced into mice alongside the low-protein diet, the animals gained less weight and showed improved glucose control and lower cholesterol levels, according to the news release.
The researchers also found that the microbes did not act through a single pathway. One microbial signal altered bile acids in a way that nudged fat tissue toward a calorie-burning state. A second signal prompted the liver to release FGF21, a hormone involved in metabolism. When scientists interrupted either signal, the beiging effect disappeared, suggesting both signals were required.
“This work underscores how the gut microbiome is actively interpreting what we eat and translating that information into signals the body responds to,” said Ramnik Xavier, M.D., Ph.D., a co-senior author, a core member at the Broad Institute and a professor of medicine at Harvard Medical School.
For readers, the most important takeaway is what this study does and does not suggest. It strengthens the case that the gut microbiome is not just along for the ride, but can help convert dietary cues into metabolic changes. It does not mean people should adopt an extreme low-protein diet, and it does not show a proven strategy for weight loss or better blood sugar control in humans.
“Our goal is not to tell people to eat extreme diets,” said Takeshi Tanoue, the study’s first author at City of Hope and Keio University. “The real opportunity is to understand these pathways well enough to design therapies that safely mimic their benefits.”
“This work highlights the gut microbiome as an active decision-maker in the body,” Honda said. “It doesn’t just respond to diet — it interprets it.”
This study was supported by the Japan Agency for Medical Research and Development, the Japan Society for the Promotion of Science, Stand Up to Cancer, the Wellcome Trust, Temasek Trust, the Mitsukoshi Health and Welfare Foundation, Chugai Foundation for Innovative Drug Discovery Science, Keio University, the Broad Institute’s Infectious Disease and Microbiome Program and the National Institutes of Health.