A new study published in Science Advances by researchers at the University of Utah Health raises serious questions about the long-term safety of the ketogenic diet — the popular high-fat, low-carbohydrate eating plan that promises fast weight loss and sharper focus.
The research, conducted on mice, shows that while keto can prevent weight gain, it may also cause fatty liver disease and impair blood sugar regulation, with some harmful changes appearing in just days.
“We’ve seen short-term studies and those just looking at weight, but not really any studies looking at what happens over the longer term or with other facets of metabolic health,” said Molly Gallop, PhD, now an assistant professor of anatomy and physiology at Earlham College, who led the study as a postdoctoral fellow in nutrition and integrative physiology at U of U Health.
From Epilepsy Treatment to Diet Trend
Originally developed as a treatment for epilepsy nearly a century ago, the ketogenic diet forces the body into a metabolic state called ketosis, where fat — rather than carbohydrates — becomes the primary energy source. While short-term results can include reduced seizures, rapid fat loss, and improved insulin sensitivity, the new findings suggest that long-term effects may be more troubling.
“One thing that’s very clear is that if you have a really high-fat diet, the lipids have to go somewhere, and they usually end up in the blood and the liver,” explained Amandine Chaix, PhD, senior author of the study and assistant professor of nutrition and integrative physiology at U of U Health.
Researchers fed male and female mice one of four diets for nine months — the human equivalent of several years. Those on the classic ketogenic diet, where nearly all calories come from fat, gained less weight than mice on a Western diet. But despite staying slimmer, they developed severe metabolic complications, including fatty liver disease.
The liver damage appeared especially pronounced in male mice. Females seemed somewhat protected, and scientists plan to investigate why. The study also uncovered a paradox. After two to three months, keto-fed mice had low levels of blood sugar and insulin — seemingly positive indicators. Yet when given carbohydrates, their blood sugar spiked dangerously and stayed high.
“The problem is that when you then give these mice a little bit of carbs, their carb response is completely skewed,” said Chaix. “Their blood glucose goes really high for really long, and that’s quite dangerous.”
Further investigation showed that insulin-producing cells in the pancreas were under stress and not functioning properly. The high-fat environment appeared to damage how these cells handled proteins, disturbing their ability to secrete insulin.
A Reversible but Serious Warning
The good news: when the mice stopped the ketogenic diet, their metabolism began to recover. But the overall message remains cautionary. “I would urge anyone to talk to a health care provider if they’re thinking about going on a ketogenic diet,” Gallop advised.
If these results hold true in humans, long-term ketogenic diets may carry serious health risks, including fatty liver disease and impaired blood sugar regulation — even if the scale shows success. More research is needed to sound the alarm, but consider talking to your doctor before you start a new diet is the take home message.
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