Most people who start working out in hopes of shedding pounds wind up disappointed,a lamentable circumstance familiar to both exercisers and scientists. Multiple studies,many of them covered in this column,have found that without major changes to diet,exercise typically results in only modest weight loss at best (although it generally makes people much healthier). Quite a few exercisers lose no weight. Some gain. But there is encouraging news about physical activity and weight loss in a new study by researchers at the University of Copenhagen. It found that exercise does seem to contribute to waist-tightening,provided that the amount of exercise is neither too little nor,more strikingly,too much. For the study,a group of young men were were split into three groups. The first were assigned as non-exercisers,who served as controls,returned to their former routines,with no change to their diets or sedentary ways. The second group began 13 weeks of almost daily moderate workouts,consisting of jogging,cycling or otherwise sweating for about 30 minutes,or until each man had burned 300 calories (based on his individual metabolic rate). The third group tackled a more strenuous routine of almost hourlong workouts,during which each man burned 600 calories. At the end of the 13 weeks,the members of the control group weighed the same as they had at the start,and their body fat percentages were unchanged. On the other hand,the men who had exercised the most,working out for 60 minutes a day,had managed to drop some flab,losing an average of five pounds each. Meanwhile,the volunteers whod worked out for only 30 minutes a day did considerably better,shedding about seven pounds each,says Mads Rosenkilde,a PhD candidate at the University of Copenhagen who led the study. That impressive weight-loss windfall for the light-duty exercisers was a bit of a shock, he said. But there are hints,Rosenkilde says. Food diaries of the group burning 600 calories a day reveal that they increased the size of their meals and snacks. They also were resolutely inactive in the hours outside of exercise. The men exercising half as much,however,seemed to grow energized and inspired. They were also active in the time apart from exercise. It looks like they were taking the stairs now,not the elevators,and just moving around more. It was little things,but they add up, Rosenkilde said.
