Why can two people eat the same high-fiber meal and absorb different amounts of calories? New research from Arizona State University suggests that the answer may lie in a surprising source: methane.
The study, published in The ISME Journal, found that people whose gut microbes produce more methane tend to get more energy from food, especially fiber-rich foods, than those who produce less. These microbes, called methanogens, help other gut bacteria continue breaking down fiber by consuming excess hydrogen, a byproduct that would otherwise slow the process.
While this doesn’t mean fiber is bad — high-fiber diets still led to lower calorie absorption overall compared to processed foods — it may help explain why some people lose weight more easily than others on the same diet.
“The participants in our study were relatively healthy,” said lead author Blake Dirks. “One thing that I think would be worthy to look at is how other populations respond to these types of diets — people with obesity, diabetes or other kinds of health states.”
Researchers tested the diets in a novel way: each person lived inside a sealed, hotel-like room that precisely measured their body’s metabolism and gas output. Paired with blood and stool samples, this allowed scientists to link individual microbial profiles to differences in calorie absorption.
The findings could be a key step toward personalized nutrition, especially for diets aimed at weight loss or metabolic health.
“The diet that we designed so carefully to enhance the microbiome for this experiment had different effects on each person, in part because some people’s microbiomes produced more methane than others,” said study co-author Rosy Krajmalnik-Brown.
This study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.