Originally Posted by PoorInRichfield

While I'm certainly not on a keto diet, I started eating more "healthy fats" years ago as part of my off-the-bike diet. My experience was that it takes some time for one's body to get used to using fat as a fuel source vs carbs. After about a year of eating healthy fats (nuts, avocados, clean meats, etc.), I was amazed that I could go on my normal 40+ mile ride w/o any "snacks" and never "bonked". Heck, I'd finish a ride and not really feel all that hungry compared to when I ate carbs all the time. As far as I could tell, my rides weren't any slower on fats than on carbs, but then again, I usually ride solo at a moderately fast pace (16 - 19 mph average) and am not racing.

After doing a bit more research on the topic of carbs vs fats for cycling, the verdict seems to be that a high fat diet is good for endurance cycling, but carbs are indeed needed for shorter, high intensity workouts such as racing.