Washington: Do you eat more protein or more fat? Whatever it may be, overeating means gaining extra fat, a new study has claimed.

Researchers at the Pennington Biomedical Research Center in the US found that a habit of overeating lean chicken will put as much extra fat on the body as overeating the same number of calories in donuts or butter cookies.

As diet studies are notoriously hard to control when the participants are living their everyday lives, the researchers recruited 25 volunteers who agreed to stay in their clinic 24 hours a day, seven days a week, eating only under supervision.

For the first few weeks, the researchers monitored the volunteers' weights to calculate each person's calorie needs. Then, they overfed the volunteers by about 950 calories each day, which meant they got about 140 per cent of their actual daily needs, for eight weeks.

Calorie per calorie, "It didn't make any difference how much protein you ate, you gained the same amount of body fat," Dr George Bray, who led the research, was quoted as saying by LiveScience.

According to Dr Bray, the extra calories eaten during the eight-week study were the equivalent excess of what the typical American eats over 10 years. "It takes about 100 calories a week to replicate the current obesity epidemic."

Moreover, although the people in the low-protein group gained fewer total pounds over the course of the study, they weren't exactly healthy.

In fact, the findings, published in the Journal of the American Medical Association, raise concerns that the current recommended daily protein intake is too low, Dr Bray said.

Those on the high-protein diet gained an average of 6.49 kg by the end of the study, while those on the low-protein diet gained 3.17 kg, the researchers said.