I'm depressed because my boyfriend used to be in excellent shape but now he's been gaining weight.
What do you think will happen if he keeps gaining weight?
I'm looking forward to him leaving me when he gets back to his old weight.
While keeping in shape is important for health reasons, it really isn't something that one should break up over. You can be dissatisfied when your partner puts on weight but you should be supportive and help him try to lose weight rather than wish for him to leave you. Talk with your partner and see what exercises you can do together so that you both remain in shape.
You are right but I'll find a reason to kick him out.
You should just break up with someone if you're already making plans to dump them. It sounds like you're just looking for an excuse to get rid of him. Have you thought how he might feel to hear you so eager to break up with him?