Primarily, being overweight causes the penis to appear smaller than it actually is. But there are other, more insidious ways that obesity
contributes to the appearance of a small penis. As stated, being overweight does not make the penis actually shrink. However, as a man's belly grows, so does his pubic pad. This area at the base of the penis grows out over the penis, hiding that portion underneath a layer of fat. It's estimated that every 40-50 extra pounds a man gains hides about an inch of his penis in this way. So his penis may still technically be six inches long - but with an inch hidden away, it appears to be only five inches.
How else does a small penis result from obesity? Well, obesity is associated with erectile dysfunction
. Blood vessels are weakened by excess fat, so erections are not as full and strong, thus when the penis becomes erect, it often is not as long as it was in the past.