Morbidly Obese Toddler Undergoes Gastric Bypass Surgery Lacey Donohue · 09/19/13 08:10PM A morbidly obese two-year-old from Saudi Arabia is now the youngest person in the world to have undergone gastric bypass surgery. The child weighed 72.7 lbs and had a body mass index (BMI) of 41 when he had the surgery in 2010.