There are many weight loss plans on the market today, but Weight Watchers is one of the oldest. It began in 1961 and is still popular today. The idea behind the program is that you can eat anything you want within reason, but you'll feel fuller if you eat certain healthy foods. While you don't have to join the program, following the basic idea is the healthiest plan to lose weight. You lose weight at a slower pace but you're more likely to keep the weight off for years afterwards. The company also offers meetings to help you lose weight.