A study by University of Massachusetts Amherst researcher Barry Braun compared a group of volunteers who sat all day (they even used wheelchairs to visit the bathroom) to a group that didn't sit down at all. The difference in energy expenditure, he told The New York Times, was hundreds of calories – but the level of appetite hormones and hunger in the two groups remained identical. This is significant, because after a very hard workout, you feel hungry. And hundreds of calories a day - let's say 200 - means half a pound weight loss each week.

So how can we use this insight. Sit less. Stand rather than sit at work if you can. Fidget, get up and down if you are watching the telly. Even unvigorous movement uses up those calories.