Weight Watchers
Weight Watchers is a weight loss community and multi-national company, operating in about 30 countries. It has a science-driven approach that aims to help members lose weight by teaching healthy eating habits, recommending more exercise and providing support.
Plans are online or in-person. Online costs $29.95 to setup and $17.95/mo thereafter. In-person varies by location.
Members are provided a diet plan that stimulates weight loss by creating a calorie deficit. In the US, the primary plan offered is PointsPlus, in which members have a certain point limit per day and foods are assigned point values.