Weight Watchers

This company is the most popular globally among the top diets listed in this section, operating in more than 30 countries with its products and plans.

The Flex Plan

The Flex Plan allows its participants to eat from each food group, but assigns foods a point value. Depending on height, weight, age and physical activity, the individual has a certain allotment of points each day and can not exceed that point total. The point total can be increased, however, as physical activity increases.

Participants are also given 35 "flex points" each week, allowing them to go above their daily allotment of points if necessary.

The Core Plan

In this plan, Weight Watchers lists certain foods as "core" and restricts the amount of these foods the individual can eat. None-core foods are given normal point values, and the participant can only 21-35 points of these foods in s week. As in the Flex Plan, points can be increased with a raise in physical activity.

Once members attain target weight and stay within two pounds of that weight for six weeks, they become lifetime members, no longer charged the weekly fee for their services. The average cost per week of a Weight Watchers membership is $9 per week.

Celebrity Jenny McCarthy is Weight Watchers most-well spokesperson. Here is her story, from the Weight Watchers Web site.