<human>: Condense the text into a few key points

Just thought I'd say my boyfriend is not in any means fat, he's quite skinny actually and a little insecure about that (particularly his arms). This is not about weight loss or anything, just for the sake of his health and my own.

In the last year or so I've pretty much decided to eat healthily and get fit; I dropped a stone, actually eat 5+ a day, ran 7 miles of a marathon as part of a team yadda yadda. Thought I'd add that I was never fat, just not toned in case anyone thinks I'm projecting. My previous diet wasn't packed with fast food either, it just wasn't good food.

My boyfriend eats relatively well most of the time but is prone to eating fast food maybe once a week or crappy food a few times a week (oven pizzas, that sort of thing). He also doesn't work out at the minute. You couldn't tell though, he's always been slim, he has fast metabolism. He could tone up though which would ease his insecurities. His body has never been an attraction issue though.

However, in a few months time we'll be moving in together and I'm worried his lifestyles habits will rub off on me and I'll slowly go back to my old ways and get a bit lazy. How would you go about asking someone to eat healthier/work out without playing on his insecurities or being a dick?

I'm also a little worried he'll put on weight over the years which probably would cause an attraction issue. Personally, I don't think I could go out with someone who doesn't take care of themselves especially if I do.
<bot>: How do I ask my boyfriend to work out/be healthier without hurting his feelings? Moving in together soon and I don't want to fall back into my previous (sort of) unhealthy lifestyle