One of the most popular types of weight-loss diets today is the ketogenic diet — a diet that's high in fat and low in carbohydrates. But this type of diet may be linked to an increased risk of type 2 diabetes in the first few days of the diet, new research in animals suggests.
Though the study was done in mice — meaning more research is needed to confirm the effects in humans — experts say the work suggests that the diet could have health risks for humans.
The keto diet has been shown to help people lose weight in the short term; however, the long-term benefits of the diet aren't as clear, according to the Mayo Clinic. The diet is named for ketosis, which is the condition the body goes into when following the plan. In ketosis, the body uses ketone bodies, or water-soluble molecules produced by the liver and the breakdown of fatty tissue for cellular energy as opposed to sugars from ingested carbohydrates. And in some people, this results in weight-loss.
Still, the physiological effects of ketosis aren't fully understood. That's why researchers in Switzerland set out to better understand how ketone bodies affect molecular processes in the body, using mice as their model. But because the research was done in mice, more work is needed to see if the findings apply to humans.
In the study, the researchers fed mice a ketogenic diet for several days and expected to find a favorable outcome — perhaps weight loss or another indication of improved health. Instead, they found that the liver began resisting insulin almost immediately and the mice were unable to regulate their blood sugar levels after only three days on the diet. (Insulin resistance, meaning that cells in the body don't respond to insulin, is a key characteristic of type 2 diabetes.)
"We were expecting beneficial effects, then to our big surprise it turns out this is not the case," said senior study author Christian Wolfrum, a biochemist at ETH Zürich in Switzerland.
If the liver is resistant to insulin, that's a bad sign for the rest of the body and could mean there's an increased risk of developing type 2 diabetes, the researchers said. What's more, these results are concerning because overweight patients seeking to reduce their risk of type 2 diabetes by following a ketogenic diet could unintentionally be increasing their risk for developing the disease, at least in the first few days of their diet.
But it's important to keep in mind this is an animal study, Wolfrum told Live Science. "One cannot make any assumptions without testing this in humans," he said.
Indeed, "animal studies are wonderful when it comes to deciphering biological pathways but in translating [the findings] to humans, there's a few more steps" needed, said Teresa Fung, a nutrition scientist and dietitian at Simmons College in Boston who was not involved with the study.
Nonetheless, Fung told Live Science that she thinks the study clearly demonstrates the potential for a ketogenic diet to have a detrimental effect in humans. And, until researchers better understand the risks of those detrimental effects, she suggested that people consider other ways of accomplishing their health goals, such as trying a less-restrictive diet.
Wolfrum said he and his colleagues don't want to stop people from changing their diet if that's what's necessary to reach a healthy weight, but they think it's important for people to know that "the [final] verdict on the ketogenic diet is not out yet." There's still more research to be done to fully understand the long-term effects of a high-fat, low-carb diet. In the meantime, said Wolfrum, "more balanced food intake is probably the healthiest way to live."
Wolfrum and his colleagues published their study Wednesday (Aug. 8) in the Journal of Physiology.
Original article on Live Science.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Kimberly has a bachelor's degree in marine biology from Texas A&M University, a master's degree in biology from Southeastern Louisiana University and a graduate certificate in science communication from the University of California, Santa Cruz. She is a former reference editor for Live Science and Space.com. Her work has appeared in Inside Science, News from Science, the San Jose Mercury and others. Her favorite stories include those about animals and obscurities. A Texas native, Kim now lives in a California redwood forest.