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.
Developed by physician and cardiologist Dr. Robert Atkins, the Atkins Diet dramatically restricts the consumption of carbohydrates, while emphasizing an increased consumption of protein, fat (including saturated fat) and leafy vegetables. The Atkins plan includes 4 main phases, during which time the goal is to find your Atkins Carbyhydrate Equilibrium (ACE). Your ACE is the daily amount of carbs you can consume without gaining or losing weight. The 1st phase lasts 2 weeks and is the most restrictive with a carb intake limited to 20 net grams per day. It is designed to switch your body to a metabolic state of "ketosis" and kick start your weight loss. The 2nd phase lasts until you are 5 - 10 pounds from your goal weight. During this phase, you will gradually increase your daily net carb intake to determine how many net carbs you can consume and still maintain a healthy weight loss of 1-2 pounds per week. In the 3rd phase, you will determine your ACE, and, in the 4th phase, you will learn how use the good habits you've acquired in the previous phases to make permanent lifestyle changes.