Just remember that looks can definitely be deceiving. Take me, for example.
Just by looking at me, you could probably classify me as overweight or fat, or whatever you wanna call it. However, there is a lot more going on than you would know about. Plus, of course, there is also the "how that person got there" story that no one knows about.
Since birth, I have battled with a myriad of illnesses, mostly respiratory problems. I practically lived in the hospital for a few years when you add up all the visits. I was never really overweight, just big for my age (mostly in height). Well, one night my body gave up. I was on the verge of death. The only way that the doctors could bring me back was by bombarding my body with over a dozen different medications, including several antibiotics and steroids.
There was a period when my body chemistry was altered by the medication regimen and I would gain a lot of weight, even with the lowest-calorie, healthiest foods. My body wouldn't process nutrients properly. With 30 different medications and various forms of therapy, I'm not surprised!
The steroids ended up bulking me up a little and ruining my eyesight (nothing that a pair of glasses or contacts can't fix though, thankfully; my eyesight just won't improve, that's all). The added power that steroids gave me (it was pretty significant for a time; I remember being a young kid and being able to bodyslam some of my grown relatives when I would play and wrestle with them) helped me get my body working again so I could live.
However, some of my body is still damaged (both of my lungs are scarred, and one of them barely functions; have occasional skin problems), but I'm really healthy. All of my organs work perfectly, my blood tests come back excellent... I'm in great condition and I can give anyone a run for their money when I play around with them. Plus, after having my composition tested, I found that I have a lot of muscle, and that my bulk isn't all fat. Plus, it's not difficult for me to lose weight. If I was less busy and I could cook, I would definitely be able to get into better shape. Plus, even with my low self-esteem (which thankfully I'm learning to deal with and build upon), I don't think I'm really ugly. I think I'd be handsome if I had a better body.
Just by looking at me, you wouldn't see all of that. You'd just see the outside: an "overweight" person.
It's true that a lot of people can't help being overweight. It's just like how small-minded people can't help being assholes; it's just genetic.
EDIT: Almost forgot. When looking for a long-lasting relationship, remember that looks aren't everything, and are pretty useless when you get older. When you are 70 or 80 years old, looks won't matter. You will most likely be unable to have sex, so if your mate doesn't have a personality, things will suck. It's those times when you need someone to talk to, and share feelings with. Sex is great, but a lot of times people find that the other things in a relationship really make life sweet.