Personally, I am a supporter of a very low-fat diet and when it comes to fats, I do not add any extra fats, i.e. anything such as oils or peanut butter, etc. I only add what I have in my food. If I want a little more fat, instead of chicken I will add some lean beef or wild salmon, etc. - I like this approach for myself, not for others.
Certainly, if you stay on a very low fat diet, you can eat almost unlimited carbohydrates and not gain fat (of course, we are talking about people who already have a developed metabolism and low body fat level, because if you have excess fat to burn, low fat will not be the best choice