Okay. So we're not necessarily encouraging you to forgo food in favor of juice for a few days, but we do know it's a popular tactic in the quest to boost one's metabolism. If you're thinking about giving it a shot, the 3-Day Juice Cleanse ($180) from Life Juice is one of the most highly-rated cleanses we've found. Most reviewers seem to think they offer the best tasting juice options, which, let's be honest, is one of the most important factors when you're giving up vices like coffee, booze, cheese, and glazed pastries for three days. We're pretty sure we'd cave by the fourth hour!