Vultures are not known to die from overeating but, of course, I think it does not mean it is impossible.
I always open mine up - might learn something. The "bloat" look could be due to a clogged up intestine, a swallowed inedible object, an accumulation of liquids in the body cavity, a parasite, being gravid, etc.
When fish are gravid, they become particularly sensitive to the oxygen level in their blood - what does not affect them much when they are not gravid, kills them fast when they are. Things like oxygen concentration in the water and their ability to uptake it = gill health/function become much more important.