This could be a gut punch to keto dieters.
New research finds the low-carb, high-fat eating plan — popular among athletes, bodybuilders and some celebrities — can raise cholesterol levels and reduce beneficial gut bacteria.
“The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone,” said University of Bath professor Dylan Thompson, who oversaw the work published Monday in Cell Reports Medicine.
For the 12-week study, 53 healthy adults followed either a moderate sugar diet, a low sugar diet (less than 5% of calories from sugar) or a keto diet (less than 8% of calories from carbohydrates).
The keto diet elevated cholesterol levels, increased apolipoprotein B, which can cause plaque buildup in arteries, and decreased Bifidobacteria, carb-loving bacteria that help digest fiber, absorb nutrients and boost immunity.
“The ketogenic diet reduced fiber intake to around 15 grams per day,” explained Dr. Russell Davies, who led the research.
“This reduction in Bifidobacteria might contribute to significant long-term health consequences such as an increased risk of digestive disorders like irritable bowel disease, increased risk of intestinal infection and a weakened immune function,” he added.
The researchers instead recommend adopting a reduced sugar diet, arguing that it promotes fat loss “without apparent negative health impacts.”
Keto dieters lost an average of 6.4 pounds in 12 weeks while low sugar dieters only shed 4.6 pounds on average.
The sugar-restricted diet, however, significantly lowered cholesterol without notably altering gut bacteria.
This is not the first study to explore how a keto diet can affect the gut. 2020 research from the University of California, San Francisco determined that Bifidobacteria decreased on a short-term keto diet.
An analysis from 2022 warned that this reduction may be detrimental to colonic health and raise the risk of obesity, Type 2 diabetes and depression.
The keto plan has shown to be beneficial in some cases — it can lower blood pressure, reduce inflammation and help control seizures in children with epilepsy even as some health experts warn it’s an unsustainable, quick-fix diet.