Why we are so lazy

While fitness fans may swear by sweating it out on the treadmill, evolutionary biologists say our physiology suggests otherwise.

According to one US researcher, human biology may actually make us predisposed to laziness.

Professor Daniel Lieberman, an evolutionary biologist at Harvard University claims that in an effort to conserve energy in hard times, evolution has selected for us to do only as much exercise as is needed to survive.

Writing in a paper last year, published in the journal Current Sports Medicine Reports, Professor Lieberman explained: 'Because humans evolved to be active for play or necessity, efforts to promote exercise will require altering environments in ways that nudge or even compel people to be active and to make exercise fun.'

He argues that despite the benefits of exercise being clear to all many will opt to avoid unnecessary exertion.

From an evolutionary standpoint, all animals are adapted to be active in order to search for food and shelter, reproduce and evade the jaws of hungry predators. But humans no longer have to be "hunters and gatherers."