Water Parks attract the fat and obese because---IT'S A DAMN WATER PARK!
fat is more bouyant than muscle, and you don't have to move around as much...
The biggest aminals in the world live where---the ocean. The largest snake in the world in terms of weight, lives where? The Amazon rainforest, and typically in the swamps---where the water aids in bouyancy, thus letting the Green Anaconda supersize it's weight.
*Also, Chicago is known for it's fat and out of shape people.