An analogy to cancer is a useful way to think about it: You wouldn't remove the breasts of someone with lung cancer. Unless you were a terrible surgeon who somehow was allowed through medical school without a basic understanding of anatomy.
There are also more than 30 genes that may play a role in obesity, though it's still difficult to isolate exactly which genetic and environmental factors are most relevant. What's still poorly understood, though, is how exactly these genes interact with each other and the environment to cause obesity. And if you can't isolate the cause, a cure becomes even more difficult.
Knowing your family history helps, but it's certainly not your destiny. "While having obese parents or family members does not predestine anyone to be overweight, knowing that your genes may be particularly sensitive to foods high in sugar and saturated fat content will help you to understand your individual needs," says Dr. Caroline Apovian, director of Nutrition and Weight Management at Boston Medical Center. "Those of us with the genes that predispose us to weight gain will gain weight in an environment with plentiful, cheap, unhealthy foods."