Let’s start with saturated fat. Saturated fat is found in meat, eggs, coconut and palm oil. Saturated fat has a wonderful property in that it is very difficult to oxidize, which means two things: it doesn’t go rancid easily and it doesn’t cause oxidative stress in your body. The saturated fat in meat and eggs is a long-chain saturated fat. It is not the unhealthy fat that was once wrongfully accused as the cause of cardiovascular disease, but how healthy it is for you is still under debate. My suggestion is to not worry about it, but don’t go out of your way to eat more of it either. Coconut and palm oil contain a medium chain saturated fat and this is very special. It can actually be used directly for energy by your cells, without modification and without a spike in insulin or blood sugar. When I desperately need a snack between meals, I often choose coconut as a way of maintaining my insulin sensitivity.
Saturated fats are the only fats you should cook with on a regular basis. This is because poly-unsaturated fats do something very bad when they get heated up: they oxidize and produce Advanced Glycation End-Products (AGEs). This means two things: they do go rancid much more easily and, if they do produce AGEs, they can cause oxidative damage to the cells in your body.
“Wait, wait, wait. What are AGEs?” you say. Good question. Without delving too deeply into the biochemistry, AGEs are produced inside your body when sugar molecules (most often fructose) bind to fat or protein. The resulting molecule can cause oxidative damage and inflammation, and is generally considered to be one of the major contributors to aging. Don’t freak out too much because some production of AGEs is normal and healthy. The problem is when our bodies produce too much or when we consume too much in our food. The best way to limit your body’s production of AGEs is to limit your intake of carbohydrates, especially fructose. You don’t need to go crazy; maybe try and keep under 100g of carbohydrates a day (unless you’re trying to lose weight, and then aim for 30-50g). And while it probably isn’t as important, it’s also generally sensible to try and limit your consumption of AGEs. This means not burning your food and not cooking with polyunsaturated fats (like olive, sesame, and flax oils).
It is also important to reduce your intake of omega-6 fatty acids to the best of your ability (and budget). This means no modern vegetable oils or products made from them, like mayonnaise or store-bought salad dressings. Also, be mindful of your nut consumption and try to eat grass-fed meat, free-range poultry, and wild game whenever it’s not prohibitively expensive. At the same time, try and increase your omega-3 intake by eating more wild caught fish (canned salmon and sardines are great inexpensive options), omega-3 eggs, and maybe also using a fish oil supplement.
In summary: You still have lots of great options. You can get your “raw” fats from avocados, avocado oil, olives, olive oil, sesame oil, nuts and seeds and their oils (in moderation), and coconut and coconut products. The best sources of “cooked” fats are grass-fed meat, free-range poultry, wild game, pasture-raised or omega-3 eggs and wild-caught fish. For cooking, I suggest using a high quality extra virgin olive oil (see Olive Oil Redemption: Yes, It’s a Great Cooking Oil!), avocado oil, coconut oil (extra virgin or naturally refined), palm oil (make sure it’s ethically-sourced), grass-fed butter or ghee (if you tolerate it–many don’t, so use with caution), suet, lard, tallow or other animal fat (especially, if pasture-fed). And remember, this isn’t supposed to increase your stress. If you can only afford conventional ground beef, then don’t worry about it. Do what you can and know that you will feel better for every positive change you make!