Once your cells become insensitive to insulin, your risk of type 2 diabetes climbs. Can exercise help? Danish researchers randomly assigned 188 sedentary overweight or obese people to: ■ BIKE: start biking to work, ■ MOD: do aerobic exercise (walking, running, rowing, cycling, or cross-training) at a moderate pace, ■ VIG: do the same aerobic exercise at a vigorous pace, or ■ CON: continue their sedentary lifestyle. Each exercise group aimed to burn 320 calories a day (women) or 420 calories a day (men) on five days each week for six months. Compared to the CON group, insulin sensitivity improved 26 percent in the VIG and 20 percent in the BIKE group but only 17 percent in the MOD group, which fell below the 20 percent target. Bonus: All exercise groups lost belly fat.