My son has carried some heavy things this week.
I told him to be careful, he might get a hernia.
I told him guys are much more likely than females to get one.
Is this true? If so, why?
Hate to sound sexist, but I imagine Males are far more likely to carry heavy things. Females generally get males to do it for them in my experience.
Nothing like being both sexist and wrong. 
Hernias are protrusions of parts of tissues thru abnormal openings. The most common hernia is probably the hiatal hernia, where a portion of the stomach pushes up thru the diaphragm into the thorax.
Inguinal hernias are where a loop of bowel is pushed thru the potential space of the inguinal canal into the either the scrotum or the labia. It is more common in men because the testicles descend thru this channel, thus leaving it more ‘open’ for passage of intestines than in women, whose ovaries stay snugly in the abdomen. But hernias incarcerated in the vulva are not rare. Just less common than those in the scrotum. And heavy lifting can contribute to inguinal hernias, as it raises the intra-abdominal pressure, which can force things out of the abdomen.