The researchers at Lawrence Berkeley National Laboratory in the U.S. studied 7,000 American men to see if exercise prevented the centimeters and kilograms from collecting around their middles. It didn't. Even men who maintained a constant jogging schedule between the ages of 20 and 50 still gained an average of 1.5 kg and added almost 2 cm to their waistlines. The only way to stay slim and trim, say researchers, is to continually increase the amount of exercise with age. To keep his youthful figure, a man who ran 15 km every Saturday in his twenties would have to run a weekly 80- km marathon in his fifties.