Question: I’m 52 years old, overweight and diabetic due to lack of exercise and high body fat. I got into cycling and I love it! I want to lose weight, and a friend recommended “bonk training.” That is, don’t eat breakfast and ride till I bonk. He says my body will suck fat like crazy and get slim. Is this bogus or does it work? — Walter F.
Coach Fred Matheny Replies: That’s a really bad idea, Walter.
Sure, you burn fat when you’re out of glycogen (muscle fuel) from not eating. There’s little else to burn. But you ride very slowly and feel miserable.
Because you’re creeping along, you aren’t burning very many total calories per hour. This means you’re burning fewer fat calories, too, in comparison with having muscles well stocked with glycogen so you can go harder.
When you’re well-fueled, the percentage of fat being burned is lower. But because total caloric consumption is higher, you end up burning more total fat calories.
Besides, bonking is something to be avoided at all costs in any situation. It creates an emergency situation for your body. It thinks you’re starving. So it shuts down your metabolism because of the famine you’ve suddenly encountered.
Cycling coach Tom Ehrhard speaks to this extreme stress on a rider’s system when he says that any time you bonk, you should make the next two weeks very easy to recover. No riding near or above your lactate threshold, and certainly no racing.
I’ve done it but I didn’t empty my tank entirely. About one and a half hours early morning with nothing but black coffee. It works but no more than once every two weeks.
This is making a mountain out of a molehill. I have been “bonk” training for 15 years without knowing it. I have only bonked about five times in the last ten years. Most of the time after a few years of riding in fast groups the bonk is in the form of reduced torque and nothing else. As long as you can get home safely by yourself then all is well. At worst you stop and take a 20-minute rest under a tree or at a convenience store. In this way, I have found I can ride any distance under 100 miles using only water. I always start a morning ride in a fasted state just because I am trying to drive down my blood glucose for improved vascular health reasons. It works quite well. The body adapts.