People who are overweight
a) are always genetically predisposed to being overweight
b) lack the motivation to try to manage their weight
c) aren't necessarily well-nourished
d) have no control over the food they eat

It's not A because  not everyone has the genetics for it
I would say B because you can always change how overweight you are
It's not C because you can be well-nourished and still be overweight
And it's not D because you can control how much you eat 

Crackers. pasta. sticks. burger

C= syphilis would be the answer