Costs, Benefits and Sex

A study published in Evolution and Human Behavior found that, even after adjusting for activity levels, men require 50% more calories than women, and that muscle mass is the strongest predictor of caloric intake, stronger than occupation or BMI.

It also found another cost of being muscular: male immune systems are less effective than those of female, and become worse as muscularity increases.

But benefits were also real. More muscular men, reported having more sexual partners, in any given year and over their lifetimes.