Every year, as summer approaches, you're reminded that you're not in as good of shape as you'd like to be. And if not, there are plenty of fitness-focused articles popping up to remind you. Most promise wildly unrealistic results for a modest amount of work. Which is why you never see much difference. But this piece from Men's Journal is the simplest and most effective plan we've seen. It features a 21-day plan to turn your body around fast, designed by a Hollywood trainer who specializes in high-intensity circuit routines. The aim is to shed ten pounds of fat and pack on some muscle in just three weeks. It seems grueling at times, but no one said it would be easy.