I was PM'ing with Zigrat yesterday about this & it got me thinking a bit more about keto-adaptation and eating on long rides. I thought I'd post some of it on this thread as it's obviously relevant to the discussion. Sorry it's a bit lengthy...
But, the big issue I have is that, on those long rides, I invariably don't have the luxury of choosing what I can eat, or at least it's a limited choice (petrol station junk generally!). My understanding is that once you start introducing those simple sugars again then the body immediately switches back and all that hard-earned keto-adaptation is lost. I was recently exchanging emails with a doctor who is involved in this area of dietary research, is a real evangelist for low carb diet & training and is also a very serious cyclist. He had this to say about fuelling on the bike...
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When I go away for training weeks in majorca etc. When I am generally averaging 100-150 miles a day I tend to fuel on a homemade flapjack that's made with mostly butter, coconut oil, nuts, seeds and a bit of honey and oats to bind. But with a very small carbs content and much more fat than most flapjacks.
The only issue to try and understand is how your body deals with the repeated bouts of anaerobic metabolism you get in mountain biking.
I have used almost complete fat drinks for long distances of up to threshold road riding, but have come unstuck in group situations when the repeated hard efforts drew too much glygogen out, and its taken a carb refuel to get me back on track.
Its very hard to manage the whole situation, and takes a lot of planning. For instance, if I am off on the bike for less than 2 hours, however hard it is I know I'm best off doing it on nothing. But over 3 and I know I will need to consider carbs if there are likely to be some hard efforts that over the course of 3 hours will draw enough glycogen out. "
Clearly, he is also struggling with fitting a very low carb diet into heavy training periods. Obviously, for multi-day trips & racing it's really not practical to make up your special trail snacks beforehand & bring them all with you.
With that in mind, and because I'm quite a fussy eater, I think I'm probably edging more towards a low GI diet as something I can probably maintain long term, rather than full-on keto-adaptation. I just can't see how I can stick to it when I'm reliant on food bought along the trail, which then undoes much of the work I've done in becoming keto-adapted (or at least I think it does!). In fact, I have a suspicion that, now I'm eating fewer simple sugars in my diet, when I do eat them on a ride, I feel that the resultant insulin spike is worse. Obviously this isn't an issue if I keep popping the sugars at regular intervals on the ride, but I'm not always that organised!
Also I looked up what Mark Sisson (quite an authority on Paleo) has to say about it. Very interesting article here that suggests a low carb rather than full-blown keto-adapted diet is preferable if you still want to have the ability to effectively burn both glucose and fat...
http://www.marksdailyapple.com/what-doe ... z2BMx8vL4C
To my mind, this seems like the best approach for long distance cyclists (imho), rather than full-on ketosis. We need to maintain the ability to burn glucose when it's all that's available, without upsetting our body's heightened fat-burning capacity that we've worked hard to achieve.
