Just because..

your on a diet and/or trying to change your eating habits, even trying to gain muscle, does not mean to not eat foods with fat in it. There is a difference, there are good fats and bad fats. Obviously bad fats are foods you get from Mcdonalds and other fast food chains. Good fats, that you need in your diet to help you put on muscle and to even help burn fat, yes i said BURN FAT are in Fish, Nuts, and Vegetable Oil for example. You need these omega 3 fatty acids to help lose weight and gain muscle. It seems weird and contradicting but its true. They are essential for your body, for a healthy immune system and for fuel to burn the bad fat. So make sure your putting these into your diet in moderation.