I was just thinking about something else that may contribute to this. What about housing and enclosures? I assume in the wild it goes something like, BP smells rat in hole, BP goes in hole, eats rat, stays in hole until hungry, BP goes off looking for another rat (or something similar). Now, since they are moving and roaming between kills or looking for mates, they would get a certain degree of exercise. I keep refering to my adult male because he is a good example. Currently he is in a 50gal tank, 36 X 18 X 18. After he eats he stays in his hides for about 3 days. But after that he is out roaming the tank, sometimes for hours at night. crawling around, trying to climb the walls etc. And he will do this every night until I feed him again. So he is, in effect, getting some exercise. Now compare that to my snakes who live in a tub.
The only time I see them out of their hides is when they are drinking water, switching hides, or passing waste. They might make a lap or two around the tub then it is back in the hide. I know roaming during the day is a sign of stress, but being nocturnal means they should be "active" at night. So is it possible that by keeping them in tubs, where they only have their hides and water bowl, that we are not providing them with the space to be active and get some needed exercise. I'm not saying that tubs are all bad, just that they may benefit better in a larger, or a tub with a little more room for them to roam, explore, search for food, work all their muscles,whatever you want to call it. Applying my human logic to reptiles, it would be like going to the gym and only doing bench presses and nothing else. Your chest and arms would benefit but your legs and stomach would remain soft and flabby. Kind of like keeping a dog on a short chain with no room to run around. I know that they are not arboreal but they do seem to enjoy climbing over and around branches and things, possibly because it lets them uses their muscles in different ways and burn off some of the calories. So I'm thinking in some cases, it may be not so much over-feeding, but under-excersise. There again, we need that government grant for the research...