Sack your nutritionist. All you've done basically is starve yourself! It's all about insulin. Carbs raise insulin which promotes fat gain. You're metabolism isn't shot. You just need to understand why carbs make you fat and that eating fat spares muscle loss as long as you eat enough of it.

I understand how eating carbs help gain muscle due to the insulin boosting effect etc etc etc but you're obviously someone who doesn't do well on carbs. Don't be scared of eating fat. Be more scared of starving yourself!