High-fat diets have their fans on social media, but the pro-keto crowd is probably not cheering a recent finding that suggests a higher-fat, lower-carb diet can be bad news for your microbiome.

A study in the February issue of the journal Gut randomly assigned 217 adults to a lower-, moderate- or higher-fat diet for 6 months (total energy from fat in each diet was 20%, 30% and 40%, respectively). Researchers then tested participants to assess each diet’s effect on the population of gut bugs.

In those who consumed the highest-fat diet, researchers found higher levels of bacteria species that may cause inflammation associated with worsening health. Higher-fat diets also tend to have less dietary fiber, which is vital for a healthy microbiome.

Matthew Kadey, MS, RD

Matthew Kadey, MS, RD, is a James Beard Award–winning food journalist, dietitian and author of the cookbook Rocket Fuel: Power-Packed Food for Sport + Adventure (VeloPress 2016). He has written for dozens of magazines, including Runner’s World, Men’s Health, Shape, Men’s Fitness and Muscle and Fitness.

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