They built what they called a "vertical workstation" -- a desk fitted over a standard treadmill. They persuaded 15 obese people to work at this treadmill-desk and measured how many calories they burned.

If an overweight office worker used this vertical workstation all day, every day for a year, he or she could lose up to 66 pounds (30 kg), the researchers report in the British Journal of Sports Medicine.

James Levine and Jennifer Miller measured how many calories their 15 volunteers burned using exhaled breath but did not determine if the volunteers lost weight.

On average, their overweight volunteers burned 100 calories more every hour while walking slowly -- at 1 mile per hour (1,6 km per hour) -- than while sitting in a chair.

"If obese individuals were to replace time spent sitting at the computer with walking computer time by 2 to 3 hours a day, and if other components of energy balance were constant, a weight loss of 20 to 30 kg a year could occur," the researchers wrote.

The researchers said their desk costs approximately $1,600.

"With population body weight, workplace sedentariness and healthcare costs projected to increase, interventions that allow people to work and yet be active could help reverse obesity," they concluded.