Alright then, I'll say it again in a slightly different way.
The overweight, at least with American men, is a symptom of the problem --of losing interest in sex--and not the cause of the problem.
The same phenomenon is exhibited when other naturally free male creatures are caught, put in a pen with a female, given all the food they want to eat, and expected to copulate.
In this corollary, the physical cage is replaced by a mental "cage" of fear. Fear of saying or doing the wrong thing and displeasing his spouse, with the likely resultant catastrophic "no-fault" divorce and the loss of practically everything he has; fear of even the natural fantasizing, in which the male imagines he is with a different woman, as this could lead to infidelity--or talking in his dreams-- and the same consequences above mentioned; fear of his wife being inclined to suspect that, as a healthy, functional man, he is likely having an affair, again with the above mentioned ruinous divorce being filed against him.
Even many single men are aware of the likely existence of this situatiion if any relationship should lead to marriage, and are thus discouraged from even having any serious relationship to start with. The solution to this, as well as many other problems, is to stop making men walk tightropes in their relationships with women, by either getting rid of the no-fault divorces or any financial consequences of them. As the man is nearly always the overwhelmingly major payer in divorce, marriage is the first step to a man being legally defrauded and stripped of everything he has without having done anything wrong. Is it any wonder that they are wary of having anything to do with this and uneable, therefore, to function naturally in this area?