Originally Posted by jlippinbike

FLOUNCE wrote: The reason I moved to eating hourly was that previously I was bonking all the time, and always at the end.

JLIPPINBIKE's response:
About four years back I met a 5'7'' female triathlete at my fitness center's pool. She only weighed 119 pounds, and she sucked at swimming. My introductory line to her was with her tan lines on her thighs she looked like she was a cyclist. She replied that she was a tri-auth-lete. I laughed. I talked her into swimming with me if I could go for a bike ride or two with her. We rode a whole winter together every weekend. Each ride was 65 miles and super hilly since she loved hills. I'm kind of vertically challenged. And at the time I wasn't eating or drinking much on rides. She killed me on the rides – especially toward the end when I was “bonking.” I was annoyed to say the least. A former US national champion cyclist on the bike getting whupped by a little skinny gal who can't swim.

So what did I do? I researched this thing called “bonking.” Turns out a bonk is not exactly what I thought it was. I thought a bonk was running out of food or energy to support my physical activity. But that's not exactly true. A bonk is when your glycogen stores of carbs deplete down to nothing and thus you don't have enough glucose in your blood to support proper brain function. As I've said elsewhere, your body only has a limited ability to store carbs for energy use. And it's not so easy to replenish the glycogen stores. Regardless of your size and energy requirements I think I'm correct in saying you can only replenish something like 350 calories of carbs an hour. And if you get sloppy during a long ride replenishing carbs, then toward the end of the ride you will bonk.

The secret to avoiding bonks is to avoid many efforts during your rides that go above your threshold capacity. If you stay below your threshold, then the body won't use much of its glycogen stores. The brain will be fed. Everything will work great. But if you ride at threshold or above, then you deplete your glycogen stores. Then you will need to replenish them. When I was riding with Miss Tiny I had to bust my ass to keep up with her in the hills. And thus, by the end of the ride I was glycogen depleted since I wasn't eating all that much during the ride because I was more focused on trying to keep up with her.

By the way, this Miss Tiny was on a RAAM relay team back in 2014 that now holds the course record for their category. Took the team of four 5 days and 21 hours to go the 3020 miles. So she's no slouch on a bike.

So you might think loading up on carbs every hour is going to solve your problem. But it won't because the body will use those carbs for most of its energy requirements since that is all you are feeding it. This will cause the body to ignore the burning of fat, and especially stored body fat when you have burned all the food consumed recently.

So what do you need to strive to do? You have to figure out how fast you can go without the need to use up your glycogen stores. As long as you are not depleting your glycogen stores down to zero during rides, then you won't bonk. Moral of the story: you need to slow down a little bit during your rides so your body doesn't deplete your glycogen stores. That way you won't bonk.