Who doesnt want a magical weight-loss pill that would make calorie counting, treadmill workouts, and sacrifices unnecessary? We all do. Thats why weight-loss dietary supplements are a $3.8 billion industry. But with little federal regulation and few long-term human studies to back them up, the actual effectiveness of supplements is still open to debate.

Still, “some of them can be very useful aids to a good diet-and-exercise program,” says Harry Preuss, MD, a professor of medicine at Georgetown University and author of The Natural Fat Loss Pharmacy. Here, what the experts say about the supplements with the most promise.