Keto diet effective in mice for just a week

Yale researchers discovered that ketogenic (keto) diets result in health benefits in the short term. However, being on a keto diet for longer than roughly a week negatively impacts health. In a study on mice published in Nature Metabolism, researchers found that participating in a keto diet for a short period of time lowers diabetes risk and inflammation. This mouse study also serves as an integral first step toward initiating human clinical trials.

A keto diet derives 99% of calories from fat and protein, with the remaining 1% coming from carbohydrates. Celebrities such as LeBron James, Kim Kardashian, and Gwyneth Paltrow have praised the keto diet as an effective diet to lose weight. Due to their endorsements of the diet, it has enjoyed a recent spike in popularity.

The Yale researchers discovered that the keto diet’s impact – positive and negative – is primarily due to immune cells known as gamma delta T cells. These T cells are tissue-protective cells responsible for lowering the risk of diabetes and inflammation.

Lead author Vishwa Deep Dixit from the Yale School of Medicine explained that a keto diet effectively manipulates the body into burning fat. Because the diet has a very low carbohydrate content, one’s glucose level is greatly reduced, tricking the body into acting like it’s in the midst of starvation. Thus, the body switches its primary fuel source to fats rather than carbohydrates. Chemicals known as ketone bodies are yielded from this process. As ketone bodies are burned, tissue-protective gamma delta T cells proliferate in the body. According to Dixit, a keto diet results in an overall reduction in diabetes risk and inflammation, thereby improving metabolism. Inflammation and blood sugar levels in mice were reduced after being on the keto diet for a week.

Researchers observed that, while the body is in a starvation state, fat breakdown and fat storage both occur. Dixit said mice on the keto diet for longer than a week consumed more fat than they were able to burn and developed obesity and diabetes.

“They lose the protective gamma delta T cells in the fat,” remarked Dixit in a press release. “Before such a diet can be prescribed, a large clinical trial in controlled conditions is necessary to understand the mechanism behind metabolic and immunological benefits or any potential harm to individuals who are overweight and prediabetic.”

Emily Goldberg, postdoctoral fellow in comparative medicine at Yale, was the scientist who discerned that the keto diet results in a proliferation of gamma delta T cells in mice. Goldberg wrote, “Our findings highlight the interplay between metabolism and the immune system, and how it coordinates maintenance of healthy tissue function.”

Long-term human clinical studies are necessary to confirm the keto diet’s health benefits. With about 84 million prediabetic American adults according to the Centers for Disease Control, this research could be critical to reducing the risk of many chronic illnesses, including stroke, type 2 diabetes, and heart disease.