Doing crunches until the cows come home? Stop it! When you're down to your final inches of belly fat, the dreaded crunch won't be the exercise that finally reveals your six-pack. "You can't spot reduce," Jill says. Instead, she suggests doing functional exercises that use the muscles in your core—abdominals, back, pelvic, obliques—as well as other body parts. "These exercises use more muscles, so there is a higher rate of calorie burn while you are doing them," she says. Planks are her favorite functional exercise—they activate not just your core muscles but also your arm, leg, and butt muscles.
Having a larger waist circumference is a better indicator of health problems than commonly used measurements like body-mass index (BMI), according to a growing body of research. Specifically, having a waist size higher than 40 inches around for men or 34.5 inches for women is correlated with a higher risk for developing type 2 diabetes and heart attack. There's even evidence that having more belly fat is correlated with lower cognitive performance.