Guys, it's possible that OP's dad only put 'diet' because it was a four letter word that would relate to her gym class. My reasoning is thin, but everyone always has a reason for something, maybe his isn't so negative. He might not have been trying to tell OP to 'lose weight' at all.

Get him a lock with the combo "dick"

Well that was rude because at least you are actively doing something about it by going to the gym :)

even if your dad was trying to be helpful, he should of gone about telling you another way. he didnt need to be so harsh

Motivation!

Dads at their best.

I wonder what message he is trying to send you...

Take the hint.

not a way to inspire you.

That's actually a good password, who would guess? No one would think the password would degrade you; so, it's perfect!