完成下列各题 B The human body naturally prevents attempt(企图)to lose or gain weight．Thus the best way to lower your weight is to do some exercise daily．Although scientists don’t agree exactly how this works to lower the“setpoint”，they do know that exercise helps your body work with you and not against you in at least the following ways： 1．Exercise burns calories(卡路里)：if you walk two miles every day，you use an extra 1400 calories a week—and lose about a pound in two weeks． 2．Exercise helps to bum fat and build muscle：since muscle requires more calories than fat does，the more muscle you have，the faster you will bum calories． 3．Finally exercise speeds up your metabolism(新陈代谢)，not just while you’re exercising，but for several hours after exercise ends． A program of light-to-moderate exercise done for only a half-hour a day is enough to keep your“setpoint”lowered，and thus helps you lose weight and keep it off．If you need to lose more than five pounds，combine regular exercise with a moderate reduction in calories until you reach your goal(目标)． Scientists don’t________．