I did a cooked ketogenic high fat (80-85%), low carb, moderate protein diet for about a year and I got really bad heart problems from it. Most of my fat was coming from grain finished beef. I'd have the fattiest cuts I could find and I'd use tallow to cook it, basking the meat in it after it was done cooking. I'd also use the tallow to cook vegetables such as frozen spinach or fresh chard, or other foods such as conventional chicken wings and giblets or liver and onions or various conventionally raised pork cuts, and to cook conventional egg yolks (I'd throw the whites away). I would extract the tallow myself from fat trimmings I got from the butcher, since store-bought tallow tasted absolutely horrible. I'd make a huge batch and freeze a bunch of jars of tallow and scoop a copious amount every day to cook. I also had a ton of smoked bacon that I didn't cook any further, since it comes already cooked, and I didn't want to melt the fat away. Sometimes I'd make fried bacon and egg yolks or something, but most days I'd just have the smoked bacon cold from the fridge, and it was clearly more fat than meat by volume. I also had plenty of prosciutto which is raw ham, and salami which is a kind of very fatty raw pork+beef jerky, but they're both cured, heavily salted and usually have chemical preservatives too. All my meats had to be salted.
Most of the time, my beef was cooked blue rare (seared on the outside, raw inside, oftentimes cold inside because the heat never got to it), especially steak I'd have this way. The yolks were always super runny, just barely warm. The tallow however, was always heated. Not to the point of burning it, but it was heated. The fat on beef was always cooked also, I couldn't stand the texture of raw or undercooked beef fat. The only truly raw foods I was having were tomatoes, cucumbers, salad greens, garlic, and the occasional avocado or fruit. I'd put extra virgin olive oil in the salads, but I don't know if that was really raw or not.
For a while I was also having a lot of butter and cream and vegetable oils, but the problems really started a few months after I started packing in the tallow and giving up the other sources of fat. I also did an overfeeding experiment with the tallow, where I upped my caloric intake to well past the point of sustenance, to see if I would gain fat or gain energy. I gained energy. And heart disease.
After quitting the ketogenic diet, my heart got a little better. I didn't really stick to any particular nutritional plan, not for any more than a week anyways. I continued to eat my steaks blue rare, just didn't cook them in tallow anymore, and didn't get the fattiest cuts all the time. I started eating more fruit, and eventually grains and even junk food. The only thing that temporarily helped was raw foods. I was just too scared to eat any animal foods raw except for small amounts of fish. I went around 2.5 years like that, eating a mix of whatever depending on the day. Now that I'm 100% raw (primal) for 3.5 months it seems to be healing. For the first 2 months on this raw diet the problems seemed to have been gone completely, but now I see that there's still healing that needs to take place.
