Weight Watchers is an American-based international company that offers various dieting products and services to assist weight loss and maintenance. Founded in 1963 by Brooklyn homemaker Jean Nidetch, it now^[update] operates in about 30 countries around the world, generally under names that are local translations of “Weight Watchers”. The core philosophy behind Weight Watchers programs is to use a science-driven approach to help participants lose weight by forming helpful habits, eating smarter, getting more exercise and providing support.

The term weight-watcher, in the same sense, had circulated publicly for several years before the company was formed.

Weight Watchers' core approach is to assist members in losing weight by forming helpful habits, eating smarter, getting more exercise and providing support. No food is off limits; however, the newest plan is "taking a stand for unprocessed foods" and has adjusted the cost of items while retaining the fundamental "counting, budgeting, and planning approach" that has been the hallmark of Weight Watchers plans since the introduction of points-based counting systems. Thus, in contrast to other diets that might provide a list of foods that must be, or should never be, eaten, Weight Watchers ' primary plan has no directly comparable requirements. Participants lose weight by creating a calorie deficit; the PointsPlus system provides a framework for creating that deficit. Accordingly, Weight Watchers is generally compatible with other diet approaches and/or food intake restrictions (e.g., the paleolithic diet and South Beach diet), provided participants use the Weight Watchers framework to measure and limit the quantity of food consumed while using the other diet plan to dictate the range of acceptable food choices.