The South Beach Diet is based on the Glycemic Index, which ranks foods according to their glycemic load. The South Beach diet focuses on a healthy balance between carbs and fats - good carbs and fats. Highly processed foods like baked goods, sweets, and soft drinks will be off-limits.

Jenny Craig: The PremiseThe Jenny Craig program was founded more than 15 years ago by a woman who was struggling with her own weight. At the time, the program was unique because it offered frozen or shelf-stable prepared meals to help with portion management and calorie-intake control. Today Jenny Craig has nearly 800 centers, making it one of the largest weight-management programs in the world.

Since the early 1960s, Weight Watchers has been a kind of guru for people struggling with weight problems. The Weight Watchers program got its start when a few friends began meeting weekly to discuss how to best lose weight. That group of friends grew to millions of men and women around the world, who all follow the Weight Watchers mantra. That mantra? Dieting is just one part of long-term weight management, Weight Watchers believes.

The NutriSystem diet is less of diet and more of "meal delivery plan". Dieters who don't want to think about portion sizes, planning, shopping for or cooking meals will love the NutriSystem diet plan. You simply make your food selections and then get a month's worth of meals delivered to your door in microwave-ready pouches. With NutriSystem diet, you receive three meals a day, plus a snack or dessert that are already cooked and shipped to you in what is called their "stay fresh" packaging. All you have to do is heat and eat.