I think you were trying to push too much food onto him. A 4 year old male is an adult, & adult male BPs usually do best on small rats (not mediums- not what you'd expect to "fit") & not being fed too often. In the wild, they don't eat as much as they're usually fed in captivity, plus they're getting a bigger appetite in the wild than when they are laying around indoors as pets. Glad you got him figured out now.