Fitness isn’t just about your weight. Crash diets can deplete healthy muscle. A good fitness program will help you reduce your body fat while retaining, or even increasing, your muscle mass. The key is knowing how much of your weight is lean and how much is fat. A body fat meter can help you track your progress. Some electronic scales include this feature, but I prefer a stand-alone model. My Omron HBF-301 is no longer made, but the Omron HBF-306, widely available online ($50-70) is very similar. (I’d like it even better if it gave me lower readings.) Technophobes can get a mechanical fat caliper, which measures the fat in a pinch of abdominal skin, for about $20.