I don't want a man dating me if I'm not what he wants. That's not useful.
Men do have to realize though that women have more chemical obstacles over time to keeping thin, and most men have a lot of trouble after 35 doing the same. So I think it's fine to prefer a particular body type or whatever, but you also need to be realistic about that body type. Some body types tend to carry more weight. Thyroid medication is the most commonly prescribed in the United States. There is a huge amount of dissatisfaction and continued issues with symptoms even when they're taking the meds to the point where they're considered to be successful at getting the proper levels again, so something is missing in getting the body chemistry right. If you care about someone you need to roll with the punches, you also need to do what you can to make it easy for your sweetheart to be healthy and to do what you can to stay healthy yourself.
It is very important though to be well-mannered about the fact that you're hoping to find a running or biking partner and you hope it will develop into true love if that's basically what your goal is. There's nothing wrong with having that kind of goal with a relationship. But a lot of men treat women like complete crap if they happen to gain weight and a lot of times it's just not as easily fixed as it seems like it should be. And long-term Health needs to be important too, you can't just be occupied with whether she's skinny enough right now because she could do something crazy like do some heavy fasting in order to please you and then hurt herself and then it will forever be much harder to get to be the proper weight. If these things were that easy everyone would do it.