[Rachyl]

If you are thin, let's say 18-19 BMI, will that affect the results and how fast the growth happens?

I was thinking of maybe gaining around 5lbs or more by drinking Ensure for a couple of weeks.

Is this advised or should I just not worry about it?

I also heard that if you have more adipose fat in your body the results are faster? As well as gaining weight by increasing my breast size I want to tone my body, but that mean losing the little fat I have and replacing it with muscle.

You need to have some fat in your body to be able to grow your breasts with the NBE. It stretches your breasts and will move or minimize the amount of fat.