Medicare doesn't disqualify you for bariatric surgery. Those who are morbidly obese -- that is, overweight by 100 pounds or more, and with a Body Mass Index of over 40 -- are covered for the necessary surgery, though follow-ups like excess skin removal may not be covered.
The sad truth is, bariatric surgery is difficult, expensive, and painful, and doesn't always work. You should always exhaust other options, especially one-on-one counseling, dieting, and exercise, and lifestyle changes, before you opt for surgery.