When Sean Milliken appeared in Season 4, he weighed 919 pounds, which at the time made him the heaviest patient in the show's history. Confined to his bed, his legs could no longer support his size, and he needed oxygen to assist his breathing.
Between his out-of-control appetite and his mother’s textbook enabling, Milliken couldn’t maintain any progress that he made. During his weight loss journey, captured on the original show and its spin-off “My 600-lb Life: Where Are They Now,” his weight fluctuated wildly between 489 and 1,003 lbs.
Unfortunately, Milliken died from cardiac arrest resulting from an infection at the age of 29. His doctor stated that massive swings in weight gains and losses placed an incredible amount of stress on his system, which had caused his heart to give out.