Weight Watchers uses a PointsPlus system to help dieters measure daily food intake and to encourage them to make healthier choices. The PointsPlus system assigns a point value to different foods, which is calculated by its protein, carbohydrate, fat, fiber and calorie content, as well as by how difficult it is for the body to work it off. Each dieter is given a unique PointsPlus target according to their gender, height, weight and weight loss goals. You can basically eat whatever you want on the Weight Watchers program, as long as you stay within your daily PointsPlus target, but you are encouraged to eat more "Power Foods," which are considered the healthiest and most filling. "Power Foods" include whole grains, lean meats, low-fat dairy and (unlimited quantities of) fresh fruit and non-starchy veggies.
The South Beach Diet was created by Dr. Arthur Agatston, a preventative cardiologist living in Miami Beach, FL and it has 3 phases. The 1st phase of the plan is the most restrictive and lasts 2 weeks. It is designed to eliminate cravings for refined starch and sugar, as well as jumpstart weight loss. During this phase, you are prohibited from all sugars, processed carbohydrates, fruits, alcohol and certain higher-glycemic vegetables. The 2nd phase will last until you reach your goal weight. During this time, you will reintroduce "good" carbs, such as whole grain bread and fruit, and are allowed to have a glass of white or red wine with dinner. The 3rd phase lasts indefinitely and is designed to help you continue using the principles you've learned in the previous phases to maintain a healthy weight for life.