Yeah, fats are crucial for good health (and very useful to balance high glycemic index/load meals and foods). It’s a complex topic, but for a few rules of thumb, you want to focus on a few things:
1. Avoid rancid fats/oils
A lot oils—polyunsaturated fats being the most prominent—are very fragile, and even a small amount of heat (as well as light and air) can make them go rancid. Hence why people who are knowledgable of smoke points will say not to cook with such and such an oil (because if you do, it will become rancid and clog up your arteries). Examples of such oils are the usual oils used for deep frying, such as canola oil, soybean oil and peanut oil.
Another important and fragile fat is cholesterol (the good kind), but if you cook it—such as scrambling your eggs every morning—you’re basically not getting the cholesterol you need and you’re eating rancid fat.
2. Be careful of not eating too much omega-6
You obviously want to completely avoid eating rancid omega-6/polyunsaturated fat, but you also want to avoid eating too much of these. The reason being that very high amounts of omega-6 can cause a host of health and cardiovascular issues. Oils high in polyunsaturated fat usually contain the most omega-6.
3. Do try to consume monounsaturated fat
Monounsaturated fat doesn’t go rancid as easily (although you don’t want to cook with it). They also generally contain less omega-6. Examples of oils that contain a lot of monounsaturated fat are oils such as olive oil, avocado oil and macadamia nut oil.
4. Read up on modern scientific research about saturated fat
The research that was used to vilify saturated fat dates back to the 1960’s, by a man named Ancel Keys. He tried to reduce cardiovascular disease, but vilifying saturated fat resulted in cardiovascular disease skyrocketing (go figure). I won’t say anything else other than to do your own research rather to rely on 1960’s nutrition. 