By Neil Bowdler BBC News

The full genetic picture on obesity is not complete, researchers say

Mice with the code are more likely to be primed athletic beasts, while those without laze around getting fat.

It is the second time in recent months scientists have claimed to have located genetic material linked to body weight.

Scientists in Britain said they had found a separate gene, dubbed the fat gene, linked directly to obesity.

Environmental factors

Are you the type of person who is constantly fidgeting - playing with pencils and pieces of paper, your legs jumping around under the office desk as you type?

If you are there is a chance fidgeting may be in your genes - and the good news is that you are less likely to be fat, according to the new research.

We're spending energy by [fidgeting] and this is of course one of the key factors in energy balance Prof Mathias Treier

The scientists, whose work appears in the journal Cell Metabolism, found a slice of their genome they say accounts for the propensity to shuffle and shift.

The researchers say humans have the same genetic switch shown in the mouse that pre-disposes some to fidgeting.

Lead researcher Professor Mathias Treier says those who do fidget are getting valuable daily exercise even without knowing it.

"We're spending energy by doing that - and this is of course one of the key factors in energy balance," he says.

"Clearly people who have the more fidgeting phenotype are more protected against diet-induced obesity, for example, than people who are more calm."

The way this genetic mechanism works is complicated and not fully understood - although the researchers believe this fidget molecule is also involved in appetite and our natural urge to go out and hunt down our next meal.

The UK scientists who tracked the "fat gene" said at the time it was likely to form just one part of the overall genetic profile of obesity.

Professor Treier also believes the full genetic picture is still to be completed.

He says we cannot dismiss environmental factors behind body weight.