Turn 35? Sorry, couldn't resist - I was very skinny in my 20's also, ate whatever I wanted. Then I turned 35

I think if you keep doing what you're doing, eat healthy, but as much as you want (lucky girl!). Could be you will be a muscled string bean for the rest of your life. Or everything could change when you get older, and you will need to pay close attention to how much you eat. You have the knowledge now to make the smart food choices - you are way ahead of the game.

The way I'd put on weight in my 20's was ice cream (or frozen yogurt), orange juice and a banana. Throw it in a blender for a bit, and drink up. Both my brother and I used to drink these, in addition to regular meals. He had to gain weight to be accepted into the Navy.