Going Long and Slow to Burn Calories
Most athletes looking to lose weight stick to long, slow cardio workouts, since the maximum fat-burning rate occurs at moderate exercise intensity (a.k.a. the fat zone). But if you're looking to trim a belt size, you need to do high-intensity intervals—they simply burn far more calories overall. Plus high-intensity exercise ramps up your resting metabolism by stimulating what's called excess post-exercise oxygen consumption (EPOC). "Your body will continue to burn calories as it replaces the oxygen you expended during your workout," says Nick Winkelman, a performance specialist with Arizona-based Athletes' Perfor­mance. Here's a simple way of looking at it: To lose weight, you need to burn more energy than you take in. High-intensity training is the most effective way to do this—especially if you get only ten hours per week to work out.

The Fix: Replace one or two weekly endurance workouts with high-intensity intervals. Example: Warm up at 65 percent of your maximum heart rate (MHR) for five minutes and then do a one-to-two-minute interval at 90 to 95 percent of your MHR. Return to your warm-up pace until your heart rate drops back down to 65 percent of MHR. Repeat until you can no longer get down to 65 percent of MHR within a couple of minutes—that is, until you're sweating bullets. Then cool down.