This implies that there’s probably a max rate in terms of calories per hour that we can get out of our bodyfat.
I have around 45 pounds of body fat, which says I can only get 1674 calories per day. If that were spread over a full day, it’s only about 70 calories/hour.
Monday, at hour 41 or so of a fast, I did a bike ride. According to some other equations I found somewhere, I was riding at rates around 600 calories/hour. I felt a bit more tired and “whupped” both out there and when I got home than I normally do. Overall, though, it was a short ride - only a half hour - with an average of about 260 calories burned. It’s just the rate that seemed to matter. After about half an hour cool down, I felt normal and I went ahead and broke the fast at about 42 hours. (I also took my blood pressure and it was low-ish - 110/74).
I’d frankly never thought I’d need to think about this! It seems it might be possible that even at around 22 or 25% BF, I’m running into the limits of what I can get out of body fat.