How can I get to a normal weight without getting over weight?

most people would consider you lucky to be able to eat without gaining xD But its not good to be at 17.9 even though you are eating. Im guessing youre young, maybe a teenager? A lot of teenagers have this problem, but once they hit mid twenties (or earlier) their metabolism plummets. So you probably dont have to worry about it all your life.

But for now, this is a perfect opportunity to give your body excellent nutrition which will improve your health. You need to eat foods that contain high amounts of calories (aka. energy / kilojules)but also dense in nutrients.

For example, a handful of nuts (about 15) has almost 200 calories! Theyre good for fibre, protein and good fatty acids. Which baisically means theyre good for your heart.

Try full fat dairy products. (Full fat milk, cheese, yoghurt)

Another good one is dried fruits. A table spoon of sultanas has about 100 calories maximum. They have the same amount of nutrition as normal fruit, theyre just a lot sweeter and denser in calories. And dense breads are good. By dense breads I mean breads that have a lot of seeds on it, and feel heavy. Or just generally largge pieces of bread. Make sure theyre wholegrain though. It has high contents of fibre and can have up to 300 calories per slice.

Also, try using olive, peanut, sunflower or canola oil when youre cooking. Oil has a very high amount of fat content, and fat has a lot of calories per gram (9 calories per gram).

Although its not as dense, try eating plenty of meat, chicken, fish...

A yummy high calorie snack to have is the following:

Get a cup or so of Greek Natural Yoghurt (Full Fat), drizzle some honey on it and cut up a banana. Put the slices in and if you want, sprinkle some seeds on top. This can have up to 500 calories in one bowl! And its very tasty xD

One last thing I can think of is peanut butter and jam. Both of these spreads have high amounts of calories. Have it on a piece of wholegrain toast.

Dont stuff yourself with McDonalds or KFC, this doesnt do much good for your heart or health. Quite the oppostie actually. Just eat a lot of calorie dense foods that are nutritious, but you can have the junk foods once in a while.

If you dont wanna gain fat, or its too hard too, why not try weight training? Muscle weighs more than fat. And if you gain muscle your BMI will go up, and so will your metabolism. Its healthier than gaining fat, but if you have a skeletal figure, you probably should gain some fat.

Have fun eating =]

You should go and see a nutritionist. They would have tons of good info.