Training & Nutrition - Bonk Training: Does it really work?

Does "bonk training" really work for losing fat? Or is it just another urban legend or diet industry marketing hype?

I tried to google the subject but couldn't find any serious information about it anywhere.

Ricardo

Well, I bonked two weeks ago on a 30 mile ride. I could barely stand when I got home and was shaking violently. I lost 8.8 pounds that week. But, I DO NOT recommend it. I was messed up for days.

No it doesn't work because not being able to ride for 2-3 days afterwards really limits how many calories you can burn off in a week. And you end up eating up a lot of muscle at the same time. Eventually you hit a plateau where you're so fatigued all the time with lack of energy that you just don't want to get out and ride. Mentally you'll be drained and weary and you just want to sit around watching TV and munching on chips. Not good for weight-loss either.

A better plan is to have a system where you can get out and ride day after day over and over again. Meaning close to full-recovery every single day. This allows to increase fitness at the fastest rate and burn the most calories/hr possible. You need to structure your diet and training in a way that allows this kind of riding in order to lose fat and KEEP IT OFF. )

I think the term bonk is seriously mis-used on this forum. Bonk is not simply getting tired. Bonk is a serious depletion of you body's energy stores, primarily glycogen. Depletion to the point of near collapse, not feeling very tired. When you bonk, you can barley turn the pedals, even walking is difficult. Low gear seem too tall of gear. You weave. You are a near to total shutdown as you can be. Eating a few energy bars or gels does not relieve a true bonk, it takes hours to even start to get back to feeling OK, days to fully recover. That's bonk! I see now way you can train like that. However, you can train yourself to better mobilize fat stores by riding at the edge of glycogen depletion. That's one of the basis of a ketogenic diet, and why it takes people days to weeks to adapt to a ketogentic diet. It takes time to get the enzymatic pathways fully built up to use fat. You still will not be able to work out at a very high level, but you can do OK. I used to run 4-6 miles daily on a ketogenic diet, but it had to be relatively slow.

I think the term bonk is seriously mis-used on this forum. Bonk is not simply getting tired. Bonk is a serious depletion of you body's energy stores, primarily glycogen. Depletion to the point of near collapse, not feeling very tired. ...

I will go along with that. If someone is "bonking" regularly, either they are not really bonking or they're incredibly stupid. It is not a bonk when you feel tired after a hard effort or got dropped by your faster riding buddies -- that is just lack of training.

Anyway, bonk training sounds like a pretty dumb and unsustainable idea. I have never heard of it especially not by the 'diet industry'. Where did you hear about it (specifically?).

However, you can train yourself to better mobilize fat stores by riding at the edge of glycogen depletion. That's one of the basis of a ketogenic diet, and why it takes people days to weeks to adapt to a ketogentic diet. It takes time to get the enzymatic pathways fully built up to use fat. You still will not be able to work out at a very high level, but you can do OK. I used to run 4-6 miles daily on a ketogenic diet, but it had to be relatively slow.yeah, due to the maximum rates of lipolysis and fatty-acid uptake, there's only so many calories/hr you can generate this way. It's certainly is one way to lose weight, but yeah, you're certainly not gonna be moving very fast. Still faster than bonking though...

No it doesn't work because not being able to ride for 2-3 days afterwards really limits how many calories you can burn off in a week. And you end up eating up a lot of muscle at the same time. Eventually you hit a plateau where you're so fatigued all the time with lack of energy that you just don't want to get out and ride. Mentally you'll be drained and weary and you just want to sit around watching TV and munching on chips. Not good for weight-loss either.

A better plan is to have a system where you can get out and ride day after day over and over again. Meaning close to full-recovery every single day. This allows to increase fitness at the fastest rate and burn the most calories/hr possible. You need to structure your diet and training in a way that allows this kind of riding in order to lose fat and KEEP IT OFF. )

Exactly.

I can't imagine bonking even once a week. I bonked on Saturday and even by Friday, my legs were very weak. Anything beyond an easy pace and my legs just gave out. I was exhausted even walking up stairs.

I feel pretty much back to normal now. But even though I lost 8.8 pounds that week, I put three pounds back on this week!!! I couldn't ride for 4 days at all. And even when I did ride I had to do less mileage than planned at a lower intensity and I just felt blah.

It is far better to fuel yourself properly and keep increasing your fitness level. If you are fit and getting fitter you can continually push harder and harder, thus increasing the number of calories you burn. By building more muscle you even burn calories at rest.

No.

I can't imagine bonking even once a week. Yeah, I was figuring he wasn't really understanding the term "bonk" and was referring to near-depletion of glycogen or near-bonk. But even then, that's not a good thing... The damage it does to your body outweighs any benefits you get and it sets you back quite a bit in your training.

I think the term bonk is seriously mis-used on this forum. Bonk is not simply getting tired. Bonk is a serious depletion of you body's energy stores, primarily glycogen. Depletion to the point of near collapse, not feeling very tired. When you bonk, you can barley turn the pedals, even walking is difficult. Low gear seem too tall of gear. You weave. You are a near to total shutdown as you can be. Eating a few energy bars or gels does not relieve a true bonk, it takes hours to even start to get back to feeling OK, days to fully recover. That's bonk!

Yep. I haven't bonked in a couple of years, but the last time I did, I was 30 miles into a 40 mile ride without any food. Felt great one minute, 5 minutes later started to slow down. Couldn't figure out why. Got slower and slower. After suffering for about 30 minutes, *finally* figured out what was going on. Stopped, got some sugar to drink. Took 20 minutes before I was ready to get on the bike, and then couldn't ride more than about 12 MPH on the way home.

That's a bonk. Quick change, huge loss of power, mental confusion. No quick recovery.

Bonk training to lose fat? Pretty stupid if you ask me.

The key to losing fat is pretty easy. Eat less, eat healthy, and ride more.

There's no reason to subject your body to shock in order to burn calories.

"Bonk Training" in terms of weight loss methodology is not a true bonk like most of us think in terms of the long distance, can't stand up effect.

http://www.wtcycling.com/BonkTraining.html

1. Upon waking, drink 2-3 cups of coffee, up to 45 minutes before cycling. Don't eat.
2. Ride at endurance pace- 60-70% of your max heart rate, or a casual pace that doesn't make you pant when you talk.
3. Keep it up for 20-90 minutes.
4. You can do this on consecutive days, but mix in at least one normal breakfast per week.
5. Eat your typical breakfast as soon as the ride ends.
6 . Watch the blubber ignite!!

Well, still sounds pretty stupid to me.

a) it is not a great idea to do a hard exertion without fuel in your tank (that's asking for a bonk); and
2) for overall weight loss, the timing of the consumption of calories is not what matters; it's the count of calories relative to what you're burning. This method could really backfire for folks who are tempted to overeat immediately after a hard effort.

The other half of the equation that's not examined though is food intake. Bonk Training still requires that you eat fewer calories than you take in. If you end up binging after the ride or eat a lot for the remainder of the day, it still won't help with weight loss.

It appears that due to the limited glycogen availble, you won't be able to ride more than 60-90 minutes without bonking. That's burning off around 700-1100 calories. To lose 1-lb/week, that would require a really restricted calorie-deficit diet. You'll end up chronically fatigued and end up losing muscle. Better to ride 120-180 minutes instead and eat more...


Here's some interesting papers on caffeine & cycling:
JAP - Effect of a divided caffeine dose on endurance cycling (http://jap.physiology.org/cgi/content/full/94/4/1557?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT)

This one seems to show that caffeine without the coffee works better
JAP - Metabolic and exercise endurance effects of coffee and caffeine ingestion (http://jap.physiology.org/cgi/content/full/85/3/883)

That plan doesn't seem too out of line. 90 minutes at that pace probably doesn't require too much energy if you've eaten the night before.

At the same time, it all about calories in calories out, so it shouldn't hurt to have a little something before the ride. Also, as 'nother pointed out, it would seem to leave open the possibility for overeating.

First misunderstand the slang term "bonk". Then couple the word with a weight-loss routine and then call it bicycle training - and then - assume because some idiot put a goofy idea on a web page it must mean something.

This thread is wrong on too many levels to respond.

Hey, anyone think "food rides" work? Is that how body-builders workout?

Anyone want to discuss glycogen depletion workouts? Do you use them?

I looked a5t the link, and the suggester of the so called bonk training is Andy Pruitt, who is definitely no hack. I note that his advise is 30 minutes or so first thing AM to induce the fat burning enzyme system. That makes some sense to me. the 60-90 minute ride is unreferenced. I think I may try a low intensity first thing in the morning warm up on the trainer to see how it works.

I looked a5t the link, and the suggester of the so called bonk training is Andy Pruitt, who is definitely no hack. I note that his advise is 30 minutes or so first thing AM to induce the fat burning enzyme system. That makes some sense to me. the 60-90 minute ride is unreferenced. I think I may try a low intensity first thing in the morning warm up on the trainer to see how it works.The entire article is from Bicycling Magazine if that means anything.

Guys,
thanks for your replies. I think most of the people who took the hassle to answer my question had never heard of bonk training. Well, until a couple of weeks ago, I hadn't either. Sure bonking is not nice, but the idea is not to bonk but rather to 'almost bonk'. This training appeared first in Bycicling Magazine a few years ago and suggested that since AM hours is the time of day you have the lowest quantities of glycogen, that if you ride at an easy pace, the body will be forced to burn fat cause it doesnt have any carbs to rely on...

I didn't believe that until I saw a reality show where some obese people tried to lose great amounts of weight and they used this system and shed lots of pounds.

Ricardo

I didn't believe that until I saw a reality show where some obese people tried to lose great amounts of weight and they used this system and shed lots of pounds.


Didnt they also start doing exercise, eating better, and cutting down on portions? Was their weight loss increased by the time of day they ate/exercised or just the fact they were finally burning off more than they took in?

Cut the crap- already. There is no such thing as "bonk-training" - and if you want go out and ride on an empty stomach - then fine, but it doesn't "speed up" fatty-acid oxidation for energy consumption. (caffeine does a little)

The only thing good about empty-stomach riding is that it teaches some people to tolerate dips in their blood sugar. By riding a totally empty stomach, it is likely that a riders blood glucose will dip -thus triggering a hormonal response that involves mobilizing adipose tissues for future transport and oxidation.

The "stupid part" of this thread is the ignorance of the fact that fatty-acid-mobilization increases whether or not fresh glucose from one's diet is present. Any sub-maximal exercise promotes this metabolic activity regardless of stomach contents.

Depending on the rider's disposition, they may very well be able to have a superior "fat-burning-ride" by snacking on pure carbs before or during the ride. And because they can go longer and harder - the ride results in a larger calorie deficit that an empty stomach ride.

Exercise intensity and number of slow-twitch oxidative muscle fibers available for activity determine the rate of fatty-acid oxidation in any exercising individual. Of course, fat stores need to be available also.


Food in the stomach has very, very, little to do with it.........

Um, it's just taking a ride before breakfast, no big deal really.
If you can't ride 20 to 90 minutes on an empty stomach....
OTOH, if you think it's going to make you a new body....

Um, it's just taking a ride before breakfast, no big deal really.


Yeah. Everyone was going crazy for some reason :eek:

I used bonk training all the time back when I trained regularly (ie. summer vacation). Always worked well for me.

I used bonk training all the time back when I trained regularly (ie. summer vacation). Always worked well for me.

Did you shed pounds? If so, how many pounds? Did you ever REALLY bonked while doing it?

Thanks,

Ricardo

Cut the crap- already. There is no such thing as "bonk-training" - and if you want go out and ride on an empty stomach - then fine, but it doesn't "speed up" fatty-acid oxidation for energy consumption. (caffeine does a little)

The "stupid part" of this thread is the ignorance of the fact that fatty-acid-mobilization increases whether or not fresh glucose from one's diet is present. Any sub-maximal exercise promotes this metabolic activity regardless of stomach contents.

Exercise intensity and number of slow-twitch oxidative muscle fibers available for activity determine the rate of fatty-acid oxidation in any exercising individual. Of course, fat stores need to be available also.


Food in the stomach has very, very, little to do with it.........

Good stuff.

Muscle substrate oxidization ratios vary depending on muscle glycogen content not blood or liver glycogen levels (and of course exercise intensity). So you are correct in that food in stomach has nothing to do with fatty acid oxidization but it also extends to “food” in the liver and blood.

Bonk training typically calls for full body glycogen depletion, a very bad idea. However, one can elicit a similar effect by using up some of the muscle glycogen early in the workout. This can be accomplished by lifting one or two sets of heavy weights or by doing a couple hard efforts at the beginning of an aerobic intensity exercise session. This further enhances the endurance nature of that exercise. It all comes down to muscle fibre type and activation. The pre-fatigued type II fibres will now be harder to activate as they have low glycogen levels but the fatty acid oxidizing type I fibres will be fresh as they are not dependant on carbs. Early morning exercise does NOT have this effect. Muscle glycogen stores will have been almost entirely replenished during sleep and the only organ short of carbs will be the liver, if any.



The only thing good about empty-stomach riding is that it teaches some people to tolerate dips in their blood sugar. By riding a totally empty stomach, it is likely that a riders blood glucose will dip -thus triggering a hormonal response that involves mobilizing adipose tissues for future transport and oxidation.

Depending on the rider's disposition, they may very well be able to have a superior "fat-burning-ride" by snacking on pure carbs before or during the ride. And because they can go longer and harder - the ride results in a larger calorie deficit that an empty stomach ride.

Exactly. The energy depletion model of exercise fatigue is bogus. The “tired” feeling one experiences is due to hypoglycaemia, not due to any shortage of energy in the working muscle. Biopsies of muscles taken from extremely tired athletes still contain HUGE amounts of available energy. It is the central governor (your brain) detecting the low blood sugar, which then reduces fibre recruitment to protect the tissues from permanent damage. Proof of this can be done with electrical stimulation of muscles on fatigued subjects… the muscle can still contract… but the brain won’t tell it to. You can train-your-brain to tolerate lower levels of sugar and still agree to fire the muscle unit; but this is better done with intervals than long bonking sessions.

So moral of the story, deplete your muscle glycogen; but eat carbs during exercise to keep your blood sugars up, thus “fooling” your brain in to continuing the exercise for much longer periods.

Bonking is when you run out of fuel. It's when your blood sugar level drops too low -- exactly like an insulin reaction in a diabetic or severe hypoglycemia.

Bonking has a pretty set list of symptoms:

1. "mental" difficulties - you become irritable with little things like all of a sudden your jersey isn't comfortable or something the person riding with you says annoys you ... you start to have trouble concentrating and if you're performing mathematical calculations as you ride, like I do, all of a sudden it becomes hard to add ... you cease conversing with the people you're riding with because all of a sudden it becomes too hard to carry on a conversation.

2. hunger - maybe. I rarely feel hungry when I ride so I miss this symptom all together, but others experience it.

3. dizziness and weakness - you'll feel light headed, it's hard to focus, your legs just don't have the same power they had.

4. exhaustion - you feel really tired and you've got no energy to turn those pedals.

5. nausea - all of a sudden you just don't want to eat anymore, you feel sick and you just want to lie down somewhere.

6. vomiting, diarhea - you're well into a bonk at this point and if you've reached this point, it is very difficult to recover. But if you ever reach this point, you've got to try to get some calories inside or your situation will get much worse.

7. Coma and death ... and when you reach that stage you will lose weight ... I can guarantee it! :D


I know certain publications have called a certain type of "training" "bonk training" but I don't believe they really mean that. If they did, they would probably be up against a number of law suits from people who have taken it too far.

If what they mean is that a person should get up in the morning and take a ride anywhere from 30-90 minutes on an empty stomach, then that's a whole different thing. You've got approx. 2000 calories sitting in storage waiting to be used. Suppose you burn off 50 calories per hour while you are sleeping and you sleep for 8 hours. That's 400 calories. You'll still have 1600 calories to work with. You burn approx. 500 calories per hour, so 1600 calories is MORE than ample to take you on a 90 minute ride without touching your fat stores.

When my commute was half an hour, I'd get up in the morning and set off on my bicycle with no breakfast. I'd arrive at work just before 8 am, and wouldn't touch food till 10 am. I'm not a breakfast person. More recently my commute was about 90 minutes, and again, I'd do the whole ride with no breakfast, and then at some point after I arrived at work I'd have some whole wheat toast and honey.

Guess how much weight I lost???!!!

On the short commute ... I lost NO weight. On the long commute ... I gained weight.

Why? Because my two slices of toast and honey, combined with my lunch and other snacks I was eating throughout the day were more than enough to make up for any energy expenditure from the commute. What made the difference between the two commutes? When I was doing the long commute, I had the mistaken impression in my mind that I was burning all these calories and therefore could "reward" myself with food ... too much food, apparently. On the short commute, I had the same idea but knew I wasn't expending that much energy so I didn't eat quite as much.


Sure, riding in the morning on an empty stomach is all right ... lots of people do that ...and of course it is a good idea to exercise a minimum of 90 minutes a day, after all that's the new recommendation ... but if you want to lose weight you've got to then watch what you eat all day long, and you should aim to be active all day long through more cycling, or other activities.

So called "bonk training" all by itself doesn't work. I'm not surprised you couldn't find any serious information about it anywhere!!

Exactly. The energy depletion model of exercise fatigue is bogus. The “tired” feeling one experiences is due to hypoglycaemia, not due to any shortage of energy in the working muscle. Biopsies of muscles taken from extremely tired athletes still contain HUGE amounts of available energy. It is the central governor (your brain) detecting the low blood sugar, which then reduces fibre recruitment to protect the tissues from permanent damage. Proof of this can be done with electrical stimulation of muscles on fatigued subjects… the muscle can still contract… but the brain won’t tell it to. You can train-your-brain to tolerate lower levels of sugar and still agree to fire the muscle unit; but this is better done with intervals then long bonking sessions.

So moral of the story, deplete your muscle glycogen; but eat carbs during exercise to keep your blood sugars up, thus “fooling” your brain in to continuing the exercise for much longer periods.Exactly, that's also the mistaken assumption with the "food coma" as well. People recommend staying away from hi-GI carbs before and during rides becasue they think that it's going to cause an insulin-spike with a resultant low blood-glucose level and that some how impacts performance because they're "feeling" lethargic. But really, it's just the brain feeling the low blood-sugar. In fact, when you've eaten all that food and the insulin-spike has pumped all that glucose out of your blood-stream, where has it gone? Right into the muscles where you want it the most! :)

So blood-sugar levels and muscle-glycogen supply are two completely different measurements resulting in a cartesian-product of 4 possible states. It just happens that a lot of people measure blood-glucose because it's easier than doing muscle-biopsies. But it's really only a proxy-indicator and you really have to track & plot blood-glucose over time and account for meals & exercise in the previous 24-hours to really come up with a good prediction of muscle-glycogen.

In the end, all these "techniques" are more complicated than necessary. Just exercise and burn off more calories than you eat and it's simple to lose weight. However, keep in mind that it's not the same kind of training you'd be doing to get FAST on the bike.

I suppose we should all just email Mr Pruitt and tell him that he's wrong because bikeforums.net says so. Maybe he'll tell us how he was misquoted or something when he said it works.

I've never tried it, so I don't know if it works or not. But Pruitt's credentials aren't so bad either. To each their own.

I suppose we should all just email Mr Pruitt and tell him that he's wrong because bikeforums.net says so. Maybe he'll tell us how he was misquoted or something when he said it works.

I've never tried it, so I don't know if it works or not. But Pruitt's credentials aren't so bad either. To each their own.


Mr. Pruitt doesn't provide much background info in that article, but let's assume his overweight client is someone who does NO exercise at all, and eats "X" number of calories. Let's assume that his client is currrently either maintaining his weight, or possibly gaining very gradually.

If that client were to ride a bicycle for 90 minutes at any time of the day, and continue to eat "X" number of calories throughout the day, that overweight client would start losing weight.

It's the basic mathematical/logical forumla of ... If 'Calories Burned' are greater than 'Calories Taken In' then there will be weightloss.

There's nothing magical about getting your 90 minutes of exercise in the morning, or on an empty stomach.

Mr. Pruitt, no doubt, knows that anyone can ride 90 minutes first thing in the morning without bonking because of stored calories. He also probably knows that if he can get overweight people to do something active first thing in the morning there will be fewer excuses of the "but I'm too tired after work to exercise" sort. And he probably knows that if you can get a person active in the morning there is a greater chance that they will be inclined to do active things throughout the day because they will basically wake up with the realization that activity makes them feel good.


Incidentally a year or two ago, the surgeon general or whoever it is who makes exercise recommendations for the US, upped the recommended amount of exercise from 30-60 minutes to 60-90 minutes.


So, if the OP is looking to lose weight, he should exercise a minimum of 90 minutes a day, at whatever time of day works for him, and be sure not to increase the amount of calories he is taking in ... which can be a big danger/temptation when a person increases the amount of exercise they do.

I suppose we should all just email Mr Pruitt and tell him that he's wrong because bikeforums.net says so. Maybe he'll tell us how he was misquoted or something when he said it works. I've never tried it, so I don't know if it works or not. But Pruitt's credentials aren't so bad either. To each their own.

I'm sure Dr. Pruitt is well aware of all the factors related to training on an empty stomach. However, often editors, deadlines and paychecks can color the best judgment of very intelligent people.

It's difficult to write accurately and interestingly for the general public. Often, catch phrases, like "bonk training" are used to stimulate interest in an article.

Clearly, many of the people who have posted to this thread do not share my definition of "bonking." Nor do many forum posters understand the physiological definition of the term "training". Both terms are sloppily bantered about in this discussion. The slang-contextual usage of the terms results with a hopelessly inaccurate discussion with regard to nutritional science and physiology.

Generally, what Dr. Pruitt probably wanted to convey in his article was that a mild case of fasting hypoglycemia produced through calorie restrictive exercise could be a beneficial component of a training regimen.

The confusion regarding this subject arises from the fact experienced cyclists coined the slang term "bonking" to mean - severe exercise-induced hypoglycemia produced as a result of prolonged high-intensity exercise.

Could I have written this anymore clearly? Bonking and training do not mix. Fasting hypoglycemia is NOT bonking. Severe exercise-induced hypoglycemia is NOT training.


Burp.

Did you shed pounds? If so, how many pounds? Did you ever REALLY bonked while doing it?

Thanks,

Ricardo

I was never doing it to lose weight, since I was light enough (roughly 148-150 lb with ~ 28 in waist) back then, but I trained enough that I didn't gain weight. I'd have to look at my training logs to be sure of any specifics. My mind is a bit fuzzy, but I know I never bonked. Never came close.

And if you want to ride for a few hours, just start eating after the initial 45 minutes of "bonk training."

Um, it's just taking a ride before breakfast, no big deal really.
If you can't ride 20 to 90 minutes on an empty stomach....
OTOH, if you think it's going to make you a new body....

indeed, a person can ride a couple hundred miles on an empty stomach

its not uncommon for me to go to work on an empty stomach and not eat anything till im done, and I typically use up around 2500 calories at work

still have lots of energy left in the system from food eaten the day or night before, plus fat storage, plus glycogen in muscles and liver

To all who educated us on the definition of bonk, detrimental effects on the body, and the maladies pertaining to training, thank you, it was most informative.

To all who defined and redefined the term "bonk", you collectively wasted thousands of words. The users of bonk training should have all learned a lesson early in the thread, and called it something else like "bonk threshold training" or "near bonk training". That would have solved the problem of the bonk techies and people with prior experience with bonks ramming a definition when we are talking training.

No one bonk now ya here? And all you near bonk trainers be careful.

So moral of the story, deplete your muscle glycogen; but eat carbs during exercise to keep your blood sugars up, thus “fooling” your brain in to continuing the exercise for much longer periods.

*and* controlling your appetite after you are done, since low blood sugar makes you really hungry.

Wow, and all these years that I have been doing that, I just called it "my morning ride".

http://www.bicycling.com/article/1,6610,s1-4-22-16252-1,00.html

Bicycling had an article recently featuring this technique. Toward the end they pointedly write that is not for weight loss, it is for endurance training, and they encourge to eat a lot right after.

So does riding before breakfast not burn off excess calories and get to using up the body's fat supplies quicker, therefore being good for weight loss?

exercising oneself to total exhaustion would likely spoil my love of the bike. Just doing a 2000 feet climb is enough for me. I'd rather try to eat better.

So does riding before breakfast not burn off excess calories and get to using up the body's fat supplies quicker, therefore being good for weight loss?

For weight loss, it's all about Calories In vs. Calories Out.

It doesn't make much difference if you ride easy for 2 hours at 12 mph and burn 600 calories of mostly fat, or you ride harder for 1 hour at 18 mph and burn 600 calories of mostly glycogen. In both cases, you've burned 600 calories...assuming you don't overeat, your weight loss will be the same.

Riding before breakfast, when your glycogen stores are low, will only slow you down and/or limit the distance you can ride. It won't burn any more calories than if you were properly fueled.

Well, well, well. Having done this type of training for several years, I can report that it works. It does not slow me down or limit the distance I can ride - except that at about 2 hours duration, I really have to have something, so I start drinking energy drink at that point if my ride will be longer than that. I also limit these rides to zone 2 and 3. As to why it works, I will let the punditocracy on here argue that there's no why because it doesn't work. As for those who are interested in trying it - go for it. You never experience anything you haven't tried. Duh.

My guess is that it mostly trains the body's chemical systems - for after all that's all that training is - to do more with less fuel intake by keeping the blood sugar levels more constant. I know when I first started serious training, many years ago, I had to have something to eat or drink about every 15 minutes or I'd have difficulties with blood sugar regulation. I couldn't imagine going for 2 hours with nothing. So the upshot is that now I eat less during and after my rides than I used to, before I started this type of training, not just during these particular rides, which usually amount to only a couple a week. But during those weeks when I can do this (daylight and weather dependent), I lose about 1 lb./week. The rest of the year, nada or slight gain.

I believe Pete Penseyres holds the unofficial record for riding without eating or drinking - something like 287 miles. You wanna ride like Pete, you're gonna have to stress your systems a little.