I think their conclusion is BS.
The reality is, really stressed guys (whom can't handle the stress) will settle for obese women because their self esteem is taking a beating.
If a really stressed guy isn't already hooked up with someone, and they had two options and one was thin and sexy and the other was heavy and sexy, they would pick the thin one, if effort to achieve either was the same. But if it requires a lot more effort for option A, then they will default to option B because they just don't have the energy.