Disagreeing with facts is just willful ignorance.... There is not question as to whether snakes get fat or not. They DO. Maybe it is not always from over feeding... but I can't think of a single example where the cause wasn't over feeding....
A retic in the wild may eat something of HUGE size.. say a wild pig... no problem... but it likely wont eat again for months after that. A retic in captivity is just as capable of eating a pig but it may receive that size of a meal every month from someone who is over feeding.... this will cause obesity....
If I remember correctly, there was a zoo in Australia (?) that had that problem; their reticulated python was massively overfed & overweight and had taken on a rather nasty disposition as a result.