Spending an hour each day doing sudoko puzzles can help you keep trim, researchers have claimed.

The experts think battling with a challenging mental puzzle can burn off up to 90 calories for every 60 minutes spent trying to solve it.

While it doesn't exactly compete with the 800 calories you could burn on a treadmill in the same time, it's not bad for being sat at hoome.

It is said that while an 'at rest' mind uses 0.1 calories per minute, one which is being challenged burns through 1.5 calories every minute.

But make sure you don't have a cup of tea and chocolate biscuit while you do the sudoko - that would give you an additional 100 calories to burn off.