rato de academia

Etymology
.

Noun

 * 1) anyone addicted to physical exercise and overly concerned with the pursuit of enhancing their body muscles at any cost
 * 2) anyone who spends most of their free time at the gym, whether to exercise or just be there to chat with others

Usage notes
Although there is a feminine equivalent, masculine is generally used to refer to both men and women as it is a colloquial term.