Fight Fat at Any Age: Exercises for Your 20s, 30s, and 40s

Fitness in Your 20s

Your fitness 411: Your 20s is often a time of adventure, so take advantage of this need to explore by trying new types of workouts. "It's the perfect age to power through all types of activities, because your body is highly resilient," says Kaehler. Beware of doing too much, though -- overtraining and injuries are your biggest hurdles.

Your cardio plan: Aim to do four to six days of moderate-intensity aerobic activity for 45 to 60 minutes. "Longer workouts will help you build endurance and burn fat," says Michele Olson, PhD, a professor of exercise physiology at Auburn University in Montgomery, Alabama. Switch up your routine -- spend 10 to 15 minutes alternating between activities like the treadmill, bike, or jumping rope. Now's also a good time to train for a sprint triathlon, 10K race, or a half marathon.

Your strength needs: Strength-train one or two days a week, doing two or three sets of each move. "Always lift enough weight to struggle through your last three repetitions," says Kaehler. "If you can easily do 15 reps, gradually increase the amount of weight you're lifting."