National Weight Control Registry
The National Weight Control Registry is an American research study that includes people (18 years or older) who have lost at least 13.6 kg (30 lbs) of weight and kept it off for at least one year. There are currently over 10,000 members enrolled in the study, making it perhaps the largest study of weight loss ever conducted.
Source: Wikipedia — National Weight Control Registry (CC BY-SA 4.0)