I don't believe this story, but the NY Post is running the article as if it's legit.
A morbidly obese toddler supposedly underwent gastric bypass surgery to lose weight. He is supposedly the youngest person in the world to undergo bariatric surgery.
Bariatric surgery involves reducing the size of the stomach through a variety of surgical procedures including lap band surgery and sleeve gastrectomy (removing part of the stomach to create a stomach pouch the size of a banana).
For the record, no licensed doctor in America who values his medical license would perform such an invasive surgery on a baby.