Researchers found that people who did 20-minute kettlebell workouts torched almost 300 calories—and that's just for starters.
When you factor in the muscle-sculpting impact (the calories burned after you exercise as your body repairs its muscle fibers), the total expenditure could increase by up to 50 percent. Kettlebells also make traditional dumbbell moves more challenging.
Their weight isn't evenly distributed, so your stabilizer muscles have to work harder.
Add definition to your shoulders and back; tone your butt, core, and arms; and shed a few dress sizes with this circuit from Sean Armstead, owner of Phenomenal Fitness in Chicago.