hii friend ..
im happy that ur a pretty 16 yr old tall girl which is desired by most of the girls in India..
so its a positive thing for u . and as far as ur worry regarding ur built that ur thin is not a matter of so much concern ..as built depends mostly on genetic or hereditary factor which run in families .. and i dont suggest u to take any medicines for this problem of urs as it wil lead to many side effects with medicines like steroids ..
so i advise u to continue that good and balanced diet further ..and definitely after marriage u will gain weight .. and also with age u may gain weight so dont worry from now onwards ..
all the best and b cool and relaxed ..

Hello,
Welcome to Healthcaremagic.

You need to eat an extra 500 calories a day in order to gain one pound a week. Use the following tips to gain weight gradually while adding nutritious foods to your daily diet.

Eat six times a day - Eating three meals plus three snacks is often the easiest ways to add extra calories into the day.
Each meal should include a source of protein such as lean meat, poultry, fish, egg whites, legumes, tofu and dairy products. Protein is needed for bone health, a strong immune system and to help recover from illness.
Carbohydrates are also essential to any weight gain plan. Without enough carbohydrate calories, the body uses some protein for energy purposes rather than directing it to muscle development.
Healthy carbs such as whole-grain cereals and breads, brown rice, whole-wheat pasta, quinoa, sweet potato and fruit should be included in all meals and snacks Eating a bedtime snack can also help promote weight gain. Healthy choices include toast and nut butter, crackers and part-skim cheese, and whole-grain cereal with milk or soy beverage.
Add healthy fats - Fat is a concentrated source of calories providing roughly 120 calories a tablespoon. Adding heart-healthy unsaturated fats to meals is an easy way to sneak in calories without adding bulk, which can make you feel too full.
Include nuts and seeds -Nuts and seeds are calorie- and nutrient-dense, making them a great way to get substantial calories for a relatively small portion size. One half-cup of nuts, for example, delivers roughly 400 to 500 calories.Snack on raw or dry roasted nuts with dried fruit.
Make liquid calories count - Drinking 100-per-cent fruit juice with meals and/or snacks adds calories and nutrients. Pomegranate, cranberry, blueberry and purple grape juice are also good sources of antioxidants.

Even though exercise burns calories, it’s important to include strength training and cardiovascular exercises in your weekly routine to build and maintain muscle strength and keep your bones strong.
Be consistent in your efforts.
Take care.