From the blog:

My boyfriend has gained 30 pounds over the last four years we’ve been dating. How do I express that I am less attracted now?

Just tell him. It’s your duty to do so.

Ignore all the people who’d accuse you of being superficial or that you only go for looks and disregard character, personality and all that.

Frankly, the people who rant about how physical beauty is unimportant are either unattractive themselves or just plain lying.

It’s a moot point, but you’ve the absolute right to be attracted to whatever standards you adhere to.

You’re only being honest and you should express that honesty in your relationship with good, peaceful communication, even if it will hurt his feelings.

And why is it your duty?

Man, this is his health we’re talking about!

His family and friends are probably too polite to tell him about how crappy-looking he is today and how they’re concerned for him.

You’re the girlfriend. Be the one who stands out and give him the essential goods.

Besides, there’s nothing wrong with feeling less attracted to somebody who doesn’t do shit to take care of themselves. That’s disgusting honestly, and even more frustrating that he keeps doing it and then complains himself.

Hope this helps.