"Chair time is an insidious hazard because people haven't been told it's a hazard," said Professor Marc Hamilton of the University of Missouri in Columbia.

"The existing data, by numerous studies, are starting to show that the rates of heart disease and diabetes and obesity are doubled or sometimes even tripled in people who sit a lot."

Sitting down shuts down production of lipase, an enzyme crucial to fat absorption.

"Instead, the fat will recirculate in the blood stream and go and be stored as body fat or it can clog arteries and cause diseases," said Professor Hamilton.

Standing up reduces the levels of glucose in the blood, which could reduce the likelihood of diabetes occurring.

The average person can also expect to burn up 60 calories per hour just by standing.

"When we think about the postural muscles that are mostly in the legs and back, these are big, powerful muscles," Professor Hamilton said.

"We're talking probably 20 pounds of muscle in each leg."

"That's a lot of muscle that can be engaged in routine activities."

Such is his conviction that Professor Hamilton has got rid of his desk chair -- he now has a treadmill instead.

"If you can perform a behaviour while sitting or standing, I would choose standing," he said.

"You can have just as much fun watching your kids play if you're standing by the fence, next to a friend who pulls out that aluminium lawn chair and is sitting there."

"But just avoid the chair is the simple recommendation, as much as you can."

Professor Hamilton is confident that other researchers will pursue this idea, leading to new breakthroughs in medicine.

"There is going to be a flood of research on this in the next couple of years, and not just by us," he said.

"This has raised the attention of a lot of great scientists around the world who have begun doing their own studies."