You should try to calculate how many calories you were getting before NB and after because all those symptoms you mentioned are symptoms of malnutrition/under-eating.
I've noticed a couple people feeling better from NB looked to be from a diet where under-eating is very common and started feeling better after eating meat, a calorie-dense food, that is part of the NB diet.
This could save people a lot of money if the biggest reason people get better on NB is because they are getting more calories.