There are studies on keto-adapted athletes doing cardio, from what I can tell there is no detrimental effect from a ketogenic diet after about a month of adaptation:

https://www.sciencedirect.com/science/article/pii/0026049583...

Thanks for this, I'm doing a modified fasting regime + keto + crossfit. I started at 515#, 5 weeks ago. I'm 485 now. I have a smaller stomach from surgery in 2012 but I only lost 150 pounds after surgery (650-500). I've been yo-yoing between 450/510'ish.

My daily diet is basically a 8 carb protein shake with 60g protein around noon. Then the equivalent of 2 hamburger patties and 1/4 cup cheese for dinner. My calories rarely exceed 800 though. I feel great -- more energy than ever, and I have 0 hunger, I have to force myself to eat.

I'm hoping this is maintainable and that I can keep the momentum up. My wife has a baby due in January (our 2nd), and I want to be able to do more with the family/kids and be around for them. Luckily I have no co-morbidalities, I just did a full physical -- everything is perfect # wise blood pressure, lipids, vitamins (except D deficiency). But, I'm 38, that could change. My heart could get stressed from the weight in a few years... I've been seeing a therapist for depression, and a doctor for ADHD, and now doing a good fitness regimen.

Last year I was depressed with very dark thoughts, this year I feel great and in more control.

You don’t have to be in ketosis to burn fat for energy. Ever notice how cardio gets harder about 45 minutes in but then gets easy and you can go on for hours? That’s your body running out of stored carbs and switching to burning fat reserves.