Why Are Comfort Food Always So Fattening?

Comfort foods such as chips, chocolate and rice pudding etc may all be very high in fat and carbohydrates which results in them being fattening if eaten in large quantities.  However, nutirtionalists advise that no food is an absolute 'taboo' and that sometimes it is ok to have a little of whatever we like.
But this is where the problem lies.  Some people may like a 'little piece' of chocolate and so open a bar, but one piece leads to another and the end result is that the chocolate has finished, thereby greatly augmenting the numbers of calories consumed that day.  Similarly, it is sometimes very easy to eat two or three sticks of raw carrot, but somehow two or three chips is just never enough.
Comfort food should really only be eaten when you are not very hungry and try to ration how much you eat.  So, in essence if you can limit portion size of comfort foods, you will find that they aren't really all that fattening (just slightly moreish).