While there are no definitive studies on what constitutes a healthy diet, here is what I have found. Contrary to the recommendations of the government and nearly every dietitian in the US, a low-fat diet is NOT a reasonable way to eat. It raises bad cholesterol, and triglycerides and it encourages the consumption of too much sugar and other carbohydrates. It is the sugar that is the boogeyman in the diet not the fat. Here is a detailed description of the subject with references

https://www.westonaprice.org/health-topics/know-your-fats/the-skinny-on-fats/

The above article is a long dissertation on fats. The short version is there are several types of fat. Omega 3’s are in short supply in the Standard American Diet (SAD). Omega 6’s and Omega 9 are everywhere. Omega 3’s reduce inflammation while Omega 6’s increase inflammation. Inflammation generally equates to pain of some type. The optimal ratio is one Omega 3 to four Omega 6’s. (1:4). SAD has ratios as large as 1:24 or in some cases as 1:30. This is why I limit fried and processed foods when eating out and I take about 3 Grams of Omega 3’s per day. I started with 6 grams per day until I got my numbers back in line.

I take this product:

https://www.lifeextension.com/vitamins-supplements/item01982/super-omega-3-epa-dha-fish-oil-sesame-lignans-olive-extract

Note: Do not pay attention to the amount of fish oil. Add the EPA and DHA numbers from the Supplement Facts label to get the amount of omega 3’s in the product. Also note that it takes two soft gels to make one serving.

If you wonder where you stand, there is a test for your fat ratio. Order it from the next link. They will send you a kit for an easy finger prick. Rub the blood drop on the supplied card and send it in. You will get a report of the various levels with suggestion for what to do.

https://www.lifeextension.com/lab-testing/itemlc100066/omega-3-index-complete

The take away from this section is fairly simple. Stay away from fats that are liquid at room temperature except olive oil. While these are the very fats the medical community and the government promote as “Heart Healthy” they are known to cause inflammation and other detrimental effects in the body. In practical terms this means don’t eat ultra-processed foods, packaged foods, fast foods, fried foods, butter substitutes, nor salad dressing unless you cook them yourself and you know what kind of fats were used.

Coconut oil, palm oil, lard (Not hydrogenated), tallow, avocado oil are all good fats.