It really depends on the guy. Some guys like fat girls and some guys like skinny girls. Now NO guys wants to date a stick. All guys like their girls to have some kind of weight on them.
Now I am a guy and I have talked to other guys too. This may not be true for ALL guys but it is true for a lot of guys. There is usually like a skinny, medium, and fat. Skinny being you can see her ribs, medium being your stomach is flat but you might have what some call "love handles" and your stomach is soft, and then there is fat where your stomach is bulging out and a small bulge I would still consider medium but I am talking like a BIG bulge. You can kind of get what I am talking about here.
Now me and from the other guys I have talked to, guys usually like medium to medium fat (but closer to medium). Some guys did answer skinny BUT they said that afterwards they would like to fatten them or see them get fatter. As you get older your metabolism WILL slow down it's a scientific fact. So when you are looking for the right guy try and stay a more medium that way if you get into a real relationship and you start gaining some weight, most likely (since you already had some on you) he won't mind or it might even turn him on. :)
I also know a lot of guys that think love handles are hot while you are a medium because it shows you are soft which is what most guys want. Do not DO NOT just let yourself go completely though because there is a certain point where weight is a turn off. A little is okay but too much can be disastrous.
Hope this helps and if you ever have any questions just email me at email@example.com and I will be happy to explain myseslf further. :)