In a new study, researchers found that a ketogenic diet only produces health benefits in the short term, but negative effects after about a week.
A keto diet usually provides 99% of calories from fat and protein and only 1% from carbohydrates.
The results suggest that the keto diet might, over limited time periods, improve human health by lowering diabetes risk and inflammation.
But if the high-fat, low-carb diet is eaten beyond one week, more fat will be consumed, which can lead to diabetes and obesity.
The research was conducted by a team at Yale University.
The keto diet has become increasingly popular as celebrities, including Gwyneth Paltrow, Lebron James, and Kim Kardashian, have touted it as a weight-loss regimen.
In the study, the researchers found that the positive and negative effects of the diet both relate to immune cells called gamma delta T-cells, tissue-protective cells that lower diabetes risk and inflammation.
According to the team, a keto diet tricks the body into burning fat.
When the body’s glucose level goes down due to the diet’s low carbohydrate content, the body acts as if it is in a starvation state—although it is not—and begins burning fats instead of carbohydrates.
This process in turn yields chemicals called ketone bodies as an alternative source of fuel. When the body burns ketone bodies, tissue-protective gamma delta T-cells expand throughout the body.
This reduces diabetes risk and inflammation and improves the body’s metabolism.
The team found after a week on the keto diet, he says, mice show a reduction in blood sugar levels and inflammation.
But when the body is in this “starving-not-starving” mode, fat storage is also happening simultaneously with fat breakdown.
When mice continue to eat the high-fat, low-carb diet beyond one week they consume more fat than they can burn, and develop diabetes and obesity.
The team found the mice lost the protective gamma delta T-cells in the fat.
They say long-term clinical studies in humans will to validate the anecdotal claims of keto’s health benefits.
The lead author of the study is Vishwa Deep Dixit, a professor of comparative medicine and of immunobiology at the Yale University School of Medicine.
The study is published in Nature Metabolism.
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