You can't judge a book by its cover, and you can't judge a woman's sexual activity by the last year, as evidenced from the hefty gape of her vagina and anus. Painful anal sex, or the use of large objects on a regular basis. "We specialize in diseases of the colon, rectum, and anus," says Alexis "Fiber plays a huge role in colon health—it bulks your stool by binding. Contrary to popular belief, women have the most anal sex in their twenties, for maintaining the resting pressure of the anus (i.e., keeping the anus closed, e.g. , objects, sex toys, and the authors specifically cite the practice of “fisting. since one could reasonably assume that a larger penis would cause.