I believe that ball pythons are opportunistic feeders and by design will "fill up" on food when it's available in order to prepare their bodies for a long period of time when it is not. This is a natural adaptation to the wet/dry seasons of their native habitat (food is plentiful in the wet season, hard to find in the dry).

A ball python in captivity that is offered food too often or in large quantities will seize the opportunity to "fill up" in anticipation of the dry season that it instinctually thinks will follow this period of plentiful food. Unfortunately, when the food keeps coming and the dry season does not, the ball python will fast in order to process all of the food it stored up and then repeat the cycle over again.

I think it's far better to feed small meals once a week all year long than to deal with the unpredictability and frustration of a ball pythons fast.

-adam