A girl, 16 and BMI is 16.8. I'm underweight and I really blank what to do since I cant really gain weight even if I eat A LOT, all that it does is making my belly bloat. I have a really tiny frames and my wrist size is just as big as my little finger (exactly). I have this problem when I only have appetite only and only if I'm surrounded by a lot of people, which makes it harder. I'm a muslim, so I cant really go to the gym. I have a bar but I cant even do one pull up :( Limited time and fasting month is just around, lesser energy :/
Look you need to get more weight or add more mass to your body but it must not come from fat. Fats are terrible for you health. Muscles are great for your health, give you more strength and make you look better.
You will need both exercise and diet to get healthy weight:
To gain healthy weight you must start eating healthy. Eat more protein fibre and good carbohydrates. Eat fruits and veggies, and a lot of meat. expecially in Ramadan when you are not eating anything during day. waking up more at night and eating at night is good. Try napping during day and waking up much more early during ramadan. Eat some healthy food and then do some exercise like jogging before morning supper and then eat a lot of meat during morning meal.
You must do little running or walking to increase your metabolism and improve your bowel movements so you can eat more. And then you need to do a lot of exercises. Buy light dumbles, around 2 KG and do the exercises to target different muscles at home. You can find many videos on youtube showing easy/beginners' exercises to get beefed up.
n.b: I am talking about all-day long fast. During fast the asker can not eat anything during day.