Being on the keto diet for a long time may does more harm than good to metabolic health.
A yearlong study in mice showed that although the diet initially reduced their weight, over time it led to fatty liver disease, glucose intolerance and dangerously high cholesterol.
The ketogenic diet is a low-carb, high-fat and moderate-protein diet designed to send the body into “ketosis.”
While typically the body uses glucose from carbs to fuel itself, when deprived of this main source of energy it starts to pull glucose from the liver and muscles. After a few days, when these reserves are all used up, the body turns to stored fat and the liver converts the fat into ketones.
Keto diets are thought to help reduce the effects of treatment-resistant epilepsy, while some also believe the diet can help to reduce obesity and control type 2 diabetes, according to the study’s summary.
Foods permitted may include fish, meat and poultry, non-starchy vegetables, avocados, berries, nuts and seeds, eggs, olive oil, high-cocoa chocolate and high-fat dairy.
However, arguing there’s a gap in existing research, the study authors from the University of Utah set out to better understand the long-term impact of using a keto diet for weight loss on metabolic health.
They examined any consequences—both positive and negative—by feeding male and female mice a keto diet (89.9 percent fat) for almost one year.
They compared the keto mice with three other cohorts on a low-fat diet (LFD-10 percent fat), a standard high-fat diet (HFD-60 percent fat) and a low-fat, moderate-protein diet (LFMP-10 percent fat and 10 percent protein).
While the mice in ketosis lost weight at first, over time they developed fatty liver disease (when fat builds up in the liver), extreme glucose intolerance and hyperlipidemia (an excess of lipids or fats within the blood).
The keto mice also developed insulin sensitivity and had low insulin levels.
Lab tests and specific analysis methods linked these two outcomes to the emergence of systemic and cell-based insulin secretion dysfunction, meaning it’s not being produced or released properly.
“While our findings show that a KD both prevents and causes WL [weight loss], a KD does not lead to permanent reductions in BW [body weight] and, thus, should not be treated as a ‘cure’ for obesity or diabetes,” the study authors wrote in the paper.
“Moreover, we observed worsening glucose intolerance and impaired insulin secretion the longer the animals had been on KD, so the vision of KD as a treatment for metabolic disease should be questioned even if initial improvements in health are observed.
“Although we found that glucose intolerance caused by a KD is reversible, it is possible that other effects may persist.”
It should be noted, however, these results are based on mice and more research will be needed to see how this translates in humans.
Newsweek has reached out to the study team for additional comment.
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References
Gallop, M. R., Vieira, R. F., Mower, P. D., Matsuzaki, E. T., Liou, W., Smart, F. E., Roberts, S., Evason, K. J., Holland, W. L., & Chaix, A. (2025). A long-term ketogenic diet causes hyperlipidemia, liver dysfunction, and glucose intolerance from impaired insulin secretion in mice. Science Advances. https://doi.org/10.1126/sciadv.adx2752
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