Your goal: Get a killer body.
The game plan: High-intensity interval training (HIIT), which alternates between moderate and intense bursts of cardio. On the machine of your choice (bike, treadmill, elliptical), start with three minutes at an easy pace, then increase the speed or resistance and go hard for one minute. Repeat sequence for a total of 20 minutes, two to three times a week (give yourself 48 hours between workouts).
The proof: A small study in the Journal of Applied Physiology found that subjects who did seven HIIT sessions over two weeks increased their body's fat-burning ability by 36 percent. HIIT keeps your metabolism elevated long after you're done, so these workouts can be shorter than a normal cardio session and deliver the same results.
For details on how to perform these moves, go to oprah.com/idealworkout.
Your goal: Lower your type 2 diabetes risk.
The game plan: Cardio plus strength training. Aim for a 30-minute cardio workout five days a week. And do strength exercises, like three sets of squats, push-ups, and biceps curls (eight reps each), three times a week. [Get step-by-step instructions for how to do these moves like a pro]
The proof: A 2012 study in the Archives of Internal Medicine found that people who did both cardio and strength training for at least 2.5 hours a week each had a 59 percent lower risk of diabetes—lower than those who did only one type of exercise. While the study was done on men, researchers believe it could work for everyone, because the heart-pumping cardio incinerates body fat, while strength training helps keep blood sugar levels in a healthy range.
Your goal: Build muscle.
The game plan: Weight lifting with light weights on two to three nonconsecutive days a week. Using three- to five-pound dumbbells, perform three sets of 20 to 25 reps of the following moves: shoulder presses, dumbbell rows, chest presses, biceps curls, and squats.
The proof: A recent report from McMaster University suggests that doing more reps with lighter weights to the point of exhaustion leads to similar gains in muscle mass as fewer reps with heavier weights. Because fast-twitch muscle fibers (which contribute most to strength) are activated longer, researchers believe this could even bring about greater muscle growth.