the investigators first aim is to determine the effect of low intensity exercise (without weight loss) on insulin sensitivity, muscle lipid metabolism, and factors regulating these processes in skeletal muscle after 1 day, 2 wks, 12 wks of training, and again after 3 days without exercise in obese adults. the investigators second aim is to determine the effect of combining low intensity exercise training with 10% weight loss on insulin sensitivity, muscle lipid metabolism, and factors regulating these processes in skeletal muscle.