To figure out how many calories you burn a day, calculate your Resting Metabolic Rate (RMR)—the number of calories you burn daily doing routine activities, not including formal exercise—using this formula: RMR = bodyweight (in pounds) x 13. Next, determine how many calories you burn through exercise—a half-hour of moderate-intensity aerobic exercise burns around 350 calories in the average man, and a half-hour of lifting burns around 200. Add your RMR to the calories you burn in the gym, and keep your daily calorie consumption below that total.
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.