From my understanding, it is a sign of obesity.

Here are some more extreme examples. I believe you will have to register on that forum to see the pics.

http://www.cornsnakes.com/forums/showthread.php?t=69477
http://www.cornsnakes.com/forums/showthread.php?t=62859
http://www.cornsnakes.com/forums/showthread.php?t=74664

In any event, I don't think the snake had that shape since it was a hatchling! Sometimes people say the oddest things when they are trying to get rid of a snake. I just read on another thread where someone was sure their BP they are getting rid of was a female, due to the eggs it has layed every month or so.

I believe that a proper diet and exercise (lots of people seem to recommend swimming) will improve the situation, but I'm not sure it goes away entirely once it has developed.