Men never spend a lot of thought when it comes to building their summer bodies. They think it's easy to just spend each day in the gym and not pay too much attention to what their bodies need, unaware that their bodies grow in different ways. All progress they see is good progress, not thinking about how their rear is growing faster than any other muscles, their legs turning into huge trunks supporting a bulked ass.
They never realize this until they end up on the beach, unable to fit into any other swimwear than swim briefs that can barely manage to get past their dump truck of an ass. What confuses them is they never get attention from the girls that they want, instead getting it from massive ripped men eyeing their thick peach. It isn't long until they comply and decide to go with one, learning what it means to have their ass taken.
They never look at women again, their focus for the rest of the summer on tops willing take them home and fill their giant rear. They're just hungry bottoms now, wanting to spend the rest of their life in the gym building their glutes, allowing their bodies to continue developing into the fuck toys they were always meant to be.