I think it depends on why they gained weight. When you age, you will gain whether you like it or not; it's part of life. Your metabolism slows down and unless you decide to eat less and/or exercise more, your body will start gaining weight, but sometimes people gain weight due to being sick, or they gain weight for other factors. I've actually seen a few recent studies that say it's better to be overweight and active, rather than thin and active (
http://www.cnn.com/2011/12/05/healt...ying-shape-losing-weight/index.html?hpt=hp_c2, and
http://www.cnn.com/2011/HEALTH/08/12/obese.healthy.weightloss/index.html). Go figure! Literally!
Mind you, this again isn't an excuse for a sedentary life or poor eating habits. Regardless of size, the problem is poor eating habits and a sedentary life. That's what kills. But if you eat healthy and exercise, then sometimes you just can't beat genetics.
Young folks, just remember - when you find that guy or gal of your dreams, love them for who they are. Know them and their habits for a long time. Because eventually, the body will change. If they refuse to change their habits while you're dating, expect that it'll get that much worse when they age. Metabolism is a funny thing; when you're young, you can practically eat anything. But when your body slows down, you'll get hit with weight gain like you won't believe if you don't change!