A controlled diet high in fat and low in carbohydrate can repair kidney damage in diabetic mice, according to US scientists.
The study, published in journal PLoS ONE, showed a "ketogenic diet" could reverse damage caused to tubes in the kidneys by too much sugar in the blood.
In the UK around a third of the 2.8m people with either type 1 or 2 diabetes go on to develop kidney damage.
Diabetes UK said it was "questionable" whether humans could sustain the diet.
The researchers at the Mount Sinai School of Medicine in New York used mice with both type 1 and type 2 diabetes.
Once kidney damage had developed, half the mice were put onto the ketogenic diet for eight weeks.
The highly controlled diet, which is 87% fat, mimics the effect of starvation and should not be used without medical advice.
After eight weeks the researchers noted that kidney damage was reversed.
Professor Charles Mobbs, who led the research at Mount Sinai School of Medicine, said: "Our study is the first to show that a dietary intervention alone is enough to reverse this serious complication of diabetes.
"I certainly think it has promise, but I can't recommend it until we have done clinical trials."
The researchers also need to figure out the exact process that leads to repair.
Dr Iain Frame, director of research at Diabetes UK, said: "This research was carried out in mice so it is difficult to see how these results would translate into any real benefits for people with diabetes at this stage.
"It is too simple to say that kidney failure could be prevented by diet alone and it is also questionable whether the diet used in this model would be sustainable for humans, even in the short term."
Helen Nickerson, from the Juvenile Diabetes Research Foundation, which part funded the research, said: "Dr Mobbs' novel observation could lead to new molecular insights in diabetic kidney disease."