A、They are studying why people expend calories. B、They are studying how long people should spend on exercising. C、They are study

Have you eaten too much over the holidays? You should try fidgeting, or moving your hands or feet for a while. Those around you might not like it, but scratching and twitching is an important way of burning up calories.
    American researchers have found that some people’s squirming and wiggling equals several miles of jogging each day.
    The scientists, based at the National Institute of Health’s laboratory in Phoenix, Arizona, are studying why some people get fat and others stay slim.
    In one study, 177 people each spent 24 hours in the institute’s respiratory chamber—a room where the amount of energy people expend is measured by their oxygen and carbon dioxide levels. By the end of the day, some people had burned up 800 calories in toe-tapping, finger-drumming and other nervous habits. However, others had expended only 100 calories.
    The researchers found that slim women fidget more than fat women, but there was net significant difference in men. Heavy people expend more energy when they fidget than do thin people.