Keto diet warning: experts link trendy low-carb plan to three deadly conditions

A new study published in Science Advances links long-term, high-fat ketogenic diets to worsening metabolic health in mice, challenging the idea that the diet reliably improves metabolic outcomes. U.S. researchers tracked male and female mice on a 90 percent fat keto plan for a year and found they initially lost weight but later developed fatty liver disease, severe glucose intolerance and high blood lipids, a pattern not observed in other diet groups.

By contrast, control groups were fed a low-fat diet (10 percent fat), a standard high-fat diet (60 percent fat) and a low-fat, moderate-protein mix (10 percent fat, 10 percent protein). Across the year, the high-keto group showed insulin sensitivity with low insulin levels, while also showing hepatic steatosis and hyperlipidemia, with male mice' cholesterol higher than female's.

Dr. Molly Gallop, a postdoctoral fellow in metabolic biology at the University of Utah and co-author, said the data suggest long-term keto may undermine metabolic health: "We observed worsening glucose intolerance and impaired insulin secretion the longer the animals had been on a keto diet. Therefore, the keto diet as a treatment for metabolic disease should be questioned even if initial improvements in health are observed."

Scientists who published in Science Advances cautioned that the findings in mice may not directly translate to humans, but they stress the need for additional studies in other strains of mice, other animals and humans to determine whether keto-linked metabolic derangements are universal.

The research notes that a typical keto diet consists of roughly 75 percent fat, 20 percent protein and 5 percent carbohydrates. By comparison, the NHS healthy balanced diet recommends about 30 percent fat, 15 percent protein and 55 percent carbohydrates. People on keto are often advised to limit carbohydrates to between 20 and 50 grams per day; a single slice of wholemeal bread supplies about 14 grams, while a banana has about 20 grams, underscoring how careful meal planning must be on such a diet.

Despite rising popularity, the diet has drawn attention from celebrities. Public figures such as Gwyneth Paltrow and Jennifer Aniston have publicly discussed following a low-carb approach at various times, though Aniston has since said she eats carbohydrates in moderation. The trend has paralleled anecdotal reports of rapid early weight loss.

Experts caution that ketosis is achieved when the body shifts away from carbohydrates toward fat for energy, a state that researchers say may not be sustained in the long term. The University of Utah team called for more work to determine whether keto-related metabolic changes are specific to certain genetic backgrounds or conditions, or more broadly applicable.

Until human studies clarify the long-term risks and potential benefits, health professionals advise caution for people considering keto as a long-term lifestyle. In the meantime, researchers emphasize that a balanced diet with a varied intake of carbohydrates, fats and proteins remains the safest approach for most people.