A ketogenic diet -- which provides 99 per cent of calories from fat and protein, and only one per cent from carbohydrates -- may produce health benefits in the short term, but negative effects after about a week, according to a study conducted in mice.

The study, published in the journal Nature Metabolism, suggests that the keto diet could, over limited time periods, improve human health by lowering diabetes risk and inflammation.

The keto diet has become increasingly popular as celebrities, including Gwyneth Paltrow, and Kim Kardashian, have touted it as a weight-loss regimen, the researchers noted.

The diet tricks the body into burning fat, said lead author Vishwa Deep Dixit from the Yale University in the US.

When the body's glucose level is reduced 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, said Dixit.

After a week on the keto diet, mice show a reduction in blood sugar levels and inflammation, he said.

However, when the body is in this "starving-not-starving" mode, fat storage is also happening simultaneously with fat breakdown, the researchers said.

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 researchers said.

"They lose the protective gamma delta T-cells in the fat," Dixit said.

Long-term clinical studies in humans are still necessary to validate the anecdotal claims of keto's health benefits, the researchers noted.

"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 pre-diabetic," Dixit said.

"Obesity and type 2 diabetes are lifestyle diseases. Diet allows people a way to be in control," he said.

With the latest findings, researchers now better understand the mechanisms at work in bodies sustained on the keto diet, and why the diet may bring health benefits over limited time periods.

"Our findings highlight the interplay between metabolism and the immune system, and how it coordinates maintenance of healthy tissue function," said Emily Goldberg, a postdoctoral fellow at Yale.