Difficult to say. I didn't go to keto right away, I went to low carb first (about 20% calories from carbs) in Dec 2018. This already improved energy levels and blood pressure. Later I took on keto (April 2019), and weight started to drop. (I do suspect that my lipid cells store a lot of toxins, in fact I have to lose weight slowly or I'll feel horrible.) But the breakthrough in PPIs/heartburn and skin issues came only after I eliminated lectins and reduced oxalates, July 2019. So I did several gradual steps, and saw improvements with every step. My energy levels continued to improve slowly for several months after the last change (until the end of 2019), but I'd say energy been fairly stable for a year now.
Blood values are still improving slowly (triglycerides falling and HDL rising), which apparently is normal. Many people say blood values will stabilize when weight stabilizes, so I guess I have another 30 pounds to lose before that happens. Also sleep apnea and snoring went away after I started to consume flaxseed oil on a regular basis. Wasn't exactly planned, but I do monitor my sleep (using an old smartphone and an app that analyzes snoring), and when I started to take about 30ml flaxseed oil a day for different reasons (wanted to go high omega 3), suddenly my snoring went from 30% of the sleep duration to 0%-3%, within 2-3 days. Weird. For the last month, I snored on average less than 2% of my sleep duration. (The effect is obvious and reproducible. If I don't consume any flaxseed oil for more than 3 days or so I'll gradually start to snore again.) But apparently sleep apnea was fixed before that, when I still snored a lot, according to a sleep lab test.
Of course I remember only the successful changes
Earlier I tried a variety of things that didn't help at all. In the last few years before low carb I tried gluten free, vegan, low FODMAP and several other diets, without success. I also went carnivore for 2 months (earlier this year) and had some trouble, but I suspect I didn't eat enough fat at the time and too much protein. I plan to make another attempt at carnivore soon.
To elaborate further, my working theory is that my lipid cells store a lot of toxins (possibly from my youth, where I grew up in an area with chemistry factories all around my home city) and unhealthy fats (omega-6 linoleic acid). This would explain why I feel completely exhausted whenever I lose weight quickly (for example when I try to fast several days), and gives me some hope that I'll improve further as I'm slowly losing weight. So my plan is to keep losing weight at a slow rate (maybe 2 pounds a month), and see what happens in a year or two.