There was a great documentary I saw with an autopsy of a morbidly obese woman. The point made was that fat collects inside the body, and causes problems with the heart, liver, and other organs. Fat also emits estrogen, causing hormonal changes that can be especially problematic with men. It's why fat guys have bitch tits - they've got tons of estrogen. Separately from this, excess weight puts tons of stress in the body. Chances of arthritis go up. The sad part is this shit has been known for decades.