First of all, congrats on your healthy lifestyle!! It sounds like you know what is good for your body and have a great outlook on it.

Ummmm, hmmmmmm...the only thing I can think of to maybe help you put on some weight is to maybe start adding more carbs to your diet? Whole wheat pasta dishes, using whole wheat bread for sandwiches, etc. Or eating more nuts? Also, do you do any strength training (besides yoga/pilates, I mean using weights)? Maybe if you added a strength training routine twice a week you'd build more muscle which would increase your weight (in a good way!).

But I am sooooooooooo not an expert!! Perhaps Fit has some good ideas?

Thanks a toxicsparkle! Yeah I do weight train but only once a week, it's not my favorite. I do it carbs a lot, but I'll start eating a lot more.

Oops instead of it I meant eat. It's been one of those days!!!

I would suggest decreasing your cardio and increasing your strength training. Cardio burns calories (which you don't want), while the strength training builds muscle while burning only a moderate amount of calories.

Strength training will help build muscle and increase your body weight.
How old are you? (If you don't mind me asking) I know when I was in my teens to mid-twenties I was considered underweight as well and I ate like a horse! I was always told the only way I would increase my body weight would be through strength training. I never could get into strength training then but as I get older, my body weight is tending to maintain at the lower to middle end of "Average body weight". You may find your body will do the same.

well you do have hyper-thyroidism and being underweight is one of the main effects of that, isn't it?

I have the same problem; I eat normal and exercise yet I'm still questioned by the doctor because I am under weight. Annoying - yes, however I'm healthy and I take care of myself so I don't get extremely bothered by it. I just continue on w/ my routine. It's tough though because I don't like the fact that someone thinks I'm this way on purpose, instead of thinking that I am healthy.

^ Forgot to add that in the next week or two I'm getting my thyroid checked because I have had symptoms that go w/ a thyroid problem. Maybe that's why I'm under-weight? I'll find out soon though.

I am almost 20 years old CCY. Yeah and being under-weight is a problem for someone that has hyperthyrodism. Ahhh... strenght training is no fun.
I'll try to decrease the cardio, but it's too fun!!! I wish I could just gain weight. You always want something you can't have!

I'm having the same problem... What seems to be working for me are weight lifting, and drinking alot of milkshake type of drinks. In the past 2 months I have gained 15 healthy pounds.

I've had problems with no weight gain in the past! Now I'm very proud of my weight No one wants to be too thin!Its just not healthy!

I'm 5'10 too and i weigh 130 lbs. In the past my weight had gone down to about 120 and I upped my intake of carbs, I ate a lot of fruit in the morning, it's healthy sugar and I also increased my weight training.

You sound extremely healthy to me. I think as long as your thyroid condition is in check you shouldn't worry about it. I'm a medical student and I was told that whenever you are going by guidelines like that there will be the rare person who isn't within the curve (you know the statistics bell curve stuff). It is assumed that most people who weigh too much or too little will have health problems (and usually they do), but occasionally you'll run across a person who is fine. I say don't worry about it and keep doing what your doing. Your diet sounds perfect and that's important. If cardio is fun and your taking rest days and not putting excessive strain on your body keep it up! Good luck.