Tried it. I read "Primal Endurance" and bought it hook, line, and sinker. Gained five pounds in three months. Felt like a zombie and my breath smelled worse. It wasn't negative overall though. It lead to me tweaking my previous diet to cut out a large amount of the carbs I was consuming. The biggest advantage for me was the lack of hunger mentioned earlier. I used to take in about 75% carbs due to my level of activity. I'll burn 3000-4000 calories some days between surfing, running, metcon, and martial arts, and I was HUNGRY All. The. Time. I thought I needed tons of carbs, but it was only because my body had adapted to function that way. When I gave up on keto, I slowly reintroduced carbs until I felt normal, and I needed far less than I previously thought. I call it a success, because I feel great doing what I'm doing now. I've had a few keto-religious fanatics jump down my throat and tell me that I must have been doing it wrong, but that's ridiculous. It wasn't for me, but that doesn't mean it's not for you or somebody else. We're all different people, and we process food into energy in different ways. The Diaz bros are amazing athletes who eat pescatarian diets most of the time, and go full vegan when they're in camp. That would kill me, but it works for them. I think the big problem with workout and nutrition plans is that most people are looking for an outcome. It may be the only situation in which setting goals is a horrible idea. You can't begin a new program looking for the finish line, whether that's having abs, or just gaining xx pounds of muscle, or whatever. If you have an end goal in mind, you will fail, even if you succeed first. I think it's even a bad idea to say "I'm going to run a marathon." Great. The second you cross the finish line, you'll go back to your old shitty habits. A better way is to plan on living a life where you are able to run the marathon any time you want. Health and fitness is a lifelong journey. Keep trying different shit, but most importantly, listen to your body and just keep fucking moving.