Obesity specialist James Levine, a doctor from Mayo Clinic in Rochester, Minnesota, believes that obesity is a direct result of sitting. Recently Levine, with the help of other researchers and the Apple computer company, set up an experimental "chairless classroom" in an effort to test this theory. In this classroom, students aged 10-12 work standing up rather than sitting, although if they become tired, they are allowed a break on a floor cushion.

Levine has spent years studying non-exercise activity thermogenesis (NEAT), which is the energy expended in everyday activities. He believes that energy saving devices such as dishwashers and power mowers have decreased the amount of energy the average person expends daily. Added to the lure of sedentary activities such as television, Gameboys and computers - the result is a more obese population.

Prior to the experiment, Levine predicted that children would use about 3 times as much energy standing to do schoolwork than sitting. And early indications of energy expenditure, measured by "movement detectors" strapped onto the children's arms and legs, bears this out.

While it may be years before Levine's "chairless classroom" concept is embraced in school designs, the idea of allowing children frequent movement breaks during the school day is a healthy one.