WASHINGTON, Oct. 27 (Xinhua) -- British scientists identified a DNA mutation common in animals that may explain why a diet high in carbohydrates induces obesity and diabetes in some but not others.

The study published in the latest issue of PLOS Genetics reported a surprising difference between two sets of the fruit flies when feeding with alternate diets high in protein and high in carbohydrates.

Fruit fly larvae with a noted mitochondrial DNA (mtDNA) mutation showed a pronounced increase in development when eating high carbohydrate diet of banana, but stagnated on a high protein diet of passionfruit, according to the study.

Conversely, fruit fly larvae without that mutation thrived on the high protein diet, but dropped in frequency when put on carbohydrates.

The six-year collaborative study by Australian, American and Spanish researchers challenged the neutral theory of molecular evolution in which changes in species at the molecular level are random, not caused by natural selection and provide no benefit or disadvantage to the species.

Bill Ballard from University of New South Wales who led the study said the research was a rare demonstration of positive selection at work in evolution.

Given that humans share 75 percent of the same genes as fruit flies, and have the same mtDNA genes, it is likely, according to the study, that the same mutation inherited in human mtDNA may metabolize carbohydrates in a similar way.

"But, the news is not all bad for people harboring the mutation," said Ballard. "You would need to manage your carbohydrate intake when you are younger, but if you are unfortunate enough to develop Parkinson's Disease, a high carbohydrate diet will help you maintain weight."

"So a consequence of our study is to open up a new area for the development of specific diets and drugs to treat Parkinson's' Disease," said Ballard.