Christy Thompson/Shutterstock Weight loss is a big business, and, since it’s rarely successful in the long term, it comes with a built-in supply of repeat customers. And doctors have been involved in the business one way or another for a long time. Some 2,000 years ago, the Greek physician and philosopher Galen diagnosed “bad humors” as the cause of obesity, and prescribed massage, baths, and “slimming foods” like greens, garlic, and wild game for his overweight patients.