It's probably a lot more than that, as 1.3 million extra calories is the same as 1,000 calories surplus a day for 4 years.  Fat bodies require much more calories to maintain, so the 3,500 cal/Lb is for normal weight bodies.  (Correct me if I'm wrong.).  For a 500 lb body to just maintain would require something in the region of  6,000 calories a day.