Quick Question

I'm 16, 167cm, and weigh just over 6 stone, so yes I have a very low bmi, something like 14 i think. 

I've been eating a healthy amount (at least around 1600 cals a day, but on most days I eat lots in one sitting to make up for it which icreases it to around 2500 at least) for months now, so I'm not in'starvation mode' or whatever. 

I used to do a bit of yoga every morning, and lift 1lb weights, nothing hardcore just like a very light workout. With the onset of exams, I stopped doing this, I haven't done any yoga or exercise for months now. The only exercise I get is from walking, housework, occasional dancing around the house etc...

I know I shouldn't be doing cardio or whatever anyway because of my low bmi, but I was wondering, should I still make an effort to do SOME sort of exercise, even light yoga? I've become really lazy with that sort of thing recently, and I Just can't be bothered! I still go for walks and stuff, but I've lost that motivation I once had in the mornign. Will leading a reasonably sedentary lifestyle affect my weight gain? Will I gain it all as fat and no muscle if I continue to eat a lot and do no yoga? 

Sorry if I sound stupid or naive! 

Hi, I think with a bmi of 14 you need to go to the doctor for a physical. Your excercise can lead to a heart attack and being at such a low weight is dangerous. I know you stated you are eating a healthy amount but when you are so under and some days eating 1600 that is not healthy at all. Can you talk to your parents about getting you help? Can you work on ways to be consistent at 2500? The sedentary issue is not forever. You are sick right now and need to repair. When you get to a healthy point you can resume more activity. As my nutritionist used to say you can't build muscle out of bones. You need a healthy amount of body fat as well.

I think you probably need to eat a lot more calories per day considering your young age and low weight.  If you choose the right foods then you won't gain lots of fat.

I don't think you need to do much more exercise than you have already listed.  Perhaps join a gym and ask for advice on the best light type of exercise for your frame. 

Your BMI is so frightfully low that you really need to not worry about how your gain is affected and rather that you need to eat more and fast. You likely need more than 2500, and I should add you will not just 'gain fat'. No one does. Especially with a weight like yours you will be repairing organs, muscle and body structure by gaining weight. Please, get help.