At week 12 , the exercise group showed decreases in body weight ( mean SE ) baseline : 69.4 2.8 vs study-end : 67.6 2.7 ; P < 0.635 ) and body mass index ( BMI ) ( 25.2 1.1 vs 24.9 0.8 ; P < 0.810 ) , but the extent of change was not significantly different from that experienced by the control group ( body weight : 68.8 4.0 vs 68.8 3.9 ; BMI : 24.3 1.1 vs 24.4 1.2 ) .