About what your friend is actually doing to low carb.
But I can tell you wiht my plan, Dr Schwarzbein talks about how some of us with damaged systems, especially adrenal glands do gain weight after starting to eat what she refers to as a balanced diet.
Your body uses protien and fats to repair and maintain many of your body systems. It can't make some of those protiens and fats. That is why they are called "essential". On the other hand there are no essential carbs.
As I understand this, after years of depriving the body of the very tools it needs to rebuild and heal, you do in fact gain body weight.
I did this very thing. It can be discouraging to know that your doing what you should be but you gain. On the other hand I just now think of it as healing.
I hope that this helps.
Poofie!