The safest way to lose weight is, in most cases, to eat a nutritionally complete diet that cuts about 250 calories a day from the number of calories your body requires to maintain its present weight, plus add an exercise regime that burns an additional 250 calories a day. If you do this, you will lose about a pound a week. All of these moderate-intensity activities will burn at least 250 calories per hour for a 140-pound, healthy woman:hiking (386 calories)light gardening/yard work (302 calories)dancing (319 calories)bicycling, less than 10 mph (370 calories)tennis, singles (386 calories)walking, 3.5 mph (370 calories)yoga (336 calories)More vigorous activities, such as calisthenics, running, swimming, downhill skiing and high-speed bicycling, will burn 500 or more calories per hour.