The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".   Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.  The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.  Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.     
Today, the average American’s diet consists mainly out of processed foods, with refined carbohydrates making up the bulk of it. Let’s me give you an example: In the morning they’ll have a bowl of cereal or toast (generally white bread), some form of grain for lunch, say, a hamburger, hotdog, or sandwich, and then for dinner it might be pasta or pizza. All these processed carbs lead to spiked insulin levels. Continually elevated insulin levels cause a disruption in the central hormone pathways, and in turn can suppress testosterone production .