There are two types of fats: the unsaturated and the saturated fats. The healthy ones are the unsaturated, also called Omega-3- or rather Omega-6-fatty acids. Our body can't produce it ourselves, this is why they are essentials for us, which we should consume it with food.
These fats are really beneficial for us, because they ensure everything in the body stays supple. They also have an excellent effect on calcification of our vessels. Another advantage, what suprised me, is that they act as an inhibitor of an enzyme of fat build-up, which helps us lose weight.
Food like nuts, avocado, olive oil (olives in general), fish, even dark chocolate, and so on, are rich in unsaturated fats.
So over all, I can recommend you to take these fats on a daily basis, even if you want to lose weight. There are so many people who say that you aren't allowed to take any fats while your diet. Please dont listen to them.