If you’ve eyed a cast-iron kettle bell at your gym and couldn’t imagine a use for it beyond doorstop, keep reading. 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.
