Training & Nutrition - How do you "train your body to use fat as a fuel" instead of sugar?

I am trying to find the correct balance of nutrients for long rides. My weekly long ride is 40 miles with the group on Saturday with a breakfast stop in the middle (I work full time and have other commitments). I am working on building my endurance for longer group rides (60+ miles).

I'm a 54-year-old woman in pretty good shape for my age.:o I lost some weight several years ago by changing my lifestyle and have successfully kept it off with regular exercise and avoiding sweets (except during/after rides), heavy fatty foods, and overeating in general. This becomes tricky when I try to build and maintain muscle mass after strenuous workouts at the gym and during/after strenuous endurance rides.

I take food bars (Cliff or Nature Valley) or homemade oatmeal cookies on long rides, taking 1-2 bites every 15-30 minutes (depending on how I feel) to sustain my energy. I try to not wait until I get hungry before I eat. However, I am wondering if I should be "training my body to use fat as a fuel" rather than depending on carbs during a ride.

I am assuming this means to avoid eating during a ride just because I think I need to, and instead wait until my body tells me it needs some fuel, then take some bites, and wait again. This principle would not apply to hydration ---- e.g. I wouldn't wait until I am thirsty on a hot day before I drink.

I'd appreciate the how's and why's of this principle so I can apply it for endurance training and proper weight management.

Food does not equal energy. Just riding, you're already burning more body stores of glycogen and body fat than the energy you take in.
It sounds like you're eating when you dont have to. You're making it complicated. That's too stressful. Just ride longer and eat when you need to.
Riding on an empty stomach helps, along with having a lower carb diet in general, for teaching your body how to stop relying on little sissy bites and actually start using what it has.

You've got about 2000 calories of fuel in your liver and muscles (and this does not mean your muscles are damaged in any way when you use this fuel ... your muscles have storage cells). Burning 500 calories per hour means that you could conceivably ride 4 hours and not have to eat. However, if you want to be able to ride longer, it's a good idea to eat while riding.

The general concensus is to consume about 250 calories per hour. You're still burning more than you're eating, but by doing that you could conceivably ride 8 hours rather than just 4 hours ... and feel good the whole way through. Don't wait till you feel hungry. If you feel hungry on the bicycle, you're already in the early stages of bonking.

As for the nibbling technique ... that's a very good idea. It is difficult to eat a whole energy bar, cookie, or whatever in one go. Nibbling makes food easier to digest and encourages you to eat more and eat more regularly.

For your 40 mile rides, I would eat the 250 calories per hour for practice, because it is a good habit to get into for longer rides and it's good to find out what sits well with you when you ride. But as your ride more, and as the 40 miles becomes more and more second nature, you'll be able to get away with fewer calories consumed during the ride.

OK, I'm no physiologist but I've read a lot about this because I'm interested. You don't really have to "train" your body to use body fat as a fuel, that is what it does naturally while you're just cruising along. I believe there have been some studies that have shown it to be a good idea not to eat before you start your ride, so you have low blood sugar and will immediately start to metabolise fat for fuel. But don't overdo this, obviously. When you feel you need to eat, eat.

I have to tell you that I think a 40-mile ride is short enough for you not to have to eat at all. Certainly a 40-mile ride with a breakfast stop means that you absolutely do not need to eat on the bike. Forty miles is roughly my usual training ride on a Saturday. I go fairly hard, never take food (though plenty of water) and have never felt close to bonking for lack of energy. Sixty miles is a different matter, I'd start to nibble within a half-our or so of the start in order to ensure that I was still strong at the end. But if your long ride is 40 miles, and you want to burn fat, I'd say don't eat until it's over.

How do you "train your body to use fat as a fuel" instead of sugar?

I'm diabetic and on prednisone as well. I'd love to know the answer to that.

You've got about 2000 calories of fuel in your liver and muscles (and this does not mean your muscles are damaged in any way when you use this fuel ... your muscles have storage cells). Burning 500 calories per hour means that you could conceivably ride 4 hours and not have to eat. However, if you want to be able to ride longer, it's a good idea to eat while riding.

It needs to be pointed out that this is not really correct. You store glycogen in your muscles and liver but you don't burn glycogen exclusively when you ride. The higher the intensity, the higher the ratio of carbohydrate to fat oxidation. One could ride all day at a low intensity without burning through their glycogen stores. Personally I've ridden a lot longer than 4 hours without eating anything.

Your body burns fuel based on availability and need. Generally speaking it burns sugars first, then complex carbs, then proteins, then fat, and finally muscle.

If you eat a pre-ride meal your body will burn those calories as your ride in the above order. So if you eat a peanut butter sandwich your body will burn the sugars from the bread, then the carbs, then the protein in the PB, and finally the fat from the peanut oil.

If you use up all those calories during your ride your body will start to go to the reserves.

It's at this point your body will start using fat for energy. Only after all the other sources have been used.

So if you want to burn fat you're best to do a ride before breakfast without eating. Your performance won't be the best but you don't have to do sprint training. Just do a long sustained ride. Maybe 90 minutes at a steady pace where you can carry on a conversation without breathing heavy.

Now this isn't going to 'train' your body to burn fat. If you eat a banana on your ride your body will stop burning the fat and go back down the list. First the sugars in the banana....

http://www.google.com/hostednews/ap/article/ALeqM5h-FV-SKTR1IZ6scrSFU4b5DsCGngD9G408M80


LONDON — Running on empty may not be such a bad idea after all. Though many athletes eat before training, some scientists say that if you really want to get rid of more fat, you should skip the pre-workout snack.


Several studies suggest exercising while your body is low on food may be a good way to trim excess fat. In a recent paper, European researchers found that cyclists who trained without eating burned significantly more fat than their counterparts who ate.


Muscles usually get their energy from carbohydrates, which is why athletes like Lance Armstrong and Michael Phelps scarf down enormous amounts of food before a race. But if you haven't eaten before exercising, your body doesn't have many carbohydrates in reserve. That forces it to burn fat instead, scientists say.


"When you exercise (after fasting), your adrenalin is high and your insulin is low," said Peter Hespel, a professor of exercise physiology at the University of Leuven in Belgium. "That ratio is favorable for your muscles to oxidize (break down) more fatty acids." Hespel said that people who exercise without having eaten burn more fat than they would if they had grabbed a bite beforehand.
In a study published in April, researchers at the University of Birmingham and elsewhere assigned seven people to cycle three days a week, followed by an intense session an hour later without eating. Another seven people followed the same regime, without the instruction to fast.


Though members of the group that didn't eat performed worse on the intensive training, they burned a higher proportion of fat to carbohydrates than the group that ate. The results were published by Medicine & Science in Sports & Exercise, the journal of the American College of Sports Medicine.


In a 2008 study, Hespel and colleagues tested the effects on men who did endurance training without eating versus those who ate. In the athletes who hadn't eaten, the researchers found a spike in the amount of proteins needed to process fat, meaning their bodies had been primed through fasting to burn more fat.
Hespel recommends people do this kind of training before breakfast, since eating carbohydrates interrupts the process of metabolizing fat for about six hours afterward.

Don't waste your time and effort worrying about burning fat vs. glycogen. It's self defeating.

Concentrate on enjoying the bike ride and improving your fitness. The weight loss will come from the caloric deficit.

It needs to be pointed out that this is not really correct. You store glycogen in your muscles and liver but you don't burn glycogen exclusively when you ride. The higher the intensity, the higher the ratio of carbohydrate to fat oxidation. One could ride all day at a low intensity without burning through their glycogen stores. Personally I've ridden a lot longer than 4 hours without eating anything.+1

If you want to burn a higher percentage of fat you need to ride easier. The harder you ride the faster you'll burn through your limited (around 2000 Cals) Glycogen stores. As you gain fitness you will naturally use less glycogen and more fat at a given power output.

How hard are you riding on your long rides? Are you working close to your threshold? Experiment a little and try leaving the clif bar in your pocket and seeing how far you get before you need to eat. Drink coffee only at the breakfast stop. If you are riding at a moderate pace you should be able to get through 40 miles without any food. I wouldn't normally eat unless I'm riding hard for 3+ hrs.

+1

If you want to burn a higher percentage of fat you need to ride easier.

Percentage, yes. But you may still burn more fat calories if you ride harder.

Percentage, yes. But you may still burn more fat calories if you ride harder.

But if you ride harder, it makes you hungrier, requiring more replenishment to restore your glycogen. Riding longer at a lower pace is easier to burn off more fat and keep it off. Riding harder burns more calories but harder to keep the defecit.

You appear all confused. The topic title is about one subject and your first question is about another.

I guess what you really mean is
"What the heck can I do to be sure I am getting great results from my diet and exercise?"

The short answer is that exercising at a steady state for longer periods develops muscle fibers that use mostly oxygen and metabolize fat while they do it. Shorter, repeated bouts of intense exercise develop powerful muscle fibers that metabolize mostly sugar and increase your ability to use all energy systems.

Unless you have a very very specific set goal for your exercise sessions, then the best advice is to alternate your exercise so that some of time you go long and steady, and other time you go faster for shorter but repeated sessions.

There is no such thing as exercising for a particular metabolite like sugar or fat. My advice is sound. You exercise both ways to promote exercise volume. Exercise volume is the only variable the predicts weight control and ability to maintain weight control into the future.

It sounds as if you are doing fine.

Now, I can ride about 60 miles without eating. The thing is there is an old adage "drink before you are thirsty, eat before you are hungry". By the time you have to eat to go farther, it is really too late. You need to take something in before you run out of fuel.

Also, glycogen is a storage carbohydrate. It is easily used by the body as fuel to produce power. Fat is much harder to burn. So why do we have so much fat? Well, the energy content of fat is twice that of glycogen. So if we stored all of our reserves as glycogen instead of fat, we would have to double our fat weight and that would not be pretty.

There is another problem with fat. Fat takes twice the oxygen to yield the same amount of chemical energy (ATP) as burning carbohydrate. So if you are buring fat only, you can only generate half power. That is what happens when you *BONK*. You are burning fat and not going anywhere fast.

If you ride at near your maximum effort, you will burn almost 100% glycogen. If you back off to say 75% effort, you will probably burn about 50% fat and 50% glycogen. Say we are figuring 50 calories per mile, that would mean that at 75% effort, you would get about 2000/50 = 80 miles. I think that is a bit far for me, so I either do not cruise at 75% or I burn more calories or something.

The other thing is on multiday rides, tours and the like, you will need to replace the glycogen you used up on today's ride in order to "reload" in the evening. If you are riding long distances day after day like 80 miles plus, you will need to eat a pile of carbohydrates each day.

As to train for fat burning, I think unfit people are so unfit that virtually any activity is near 100% so they burn just about only carbohydrate. As one gets fit, as you obviously are, your body will burn significant amounts of fat when you are not pushing hard.

Another thing, your body can not make carbohydrates. The body "makes" new carbohydrates by taking proteins (usually muscle) and turning it into carbohydrate. So it is good to replace the carbohydrates you burn in your diet. It is a bit tricky because you really do not know how many calories you burn of fat and of carbohydrate. Also do not get too scared. I do not think that the body will necessarily tear up muscle to replace glycogen stores.

But your nervous system needs something like 500 calories per day (I forget the exact figure). The nervous system does not burn fat ever. So the body will burn muscle to feed the brain. That is why people die on starvation diets. They might have plenty of fat calories but their body is ripping up its muscles to feed the brain and eventually it rips up the heart.

Losing weight is tricky and a matter of balance.

You may enjoy reading the Adkins book for his theory on the subject.

You may enjoy reading the Adkins book for his theory on the subject.

Do you mean Atkins? I thought that fad was long gone.

Did they ever determine his cause of death?

Did they ever determine his cause of death?

Injuries from a fall.

It's called Bonk Training.

I don't do it, and I don't really suggest anyone else do it.

But some racers do it, and they say it works.

It's easy. Get up in the morning, ride your bike. Slowly increase
intensity/distance. Black coffee would be OK, but no calories, not even artificial sweetener.

I did try it, wasn't fun. I'm in it for the fun.

Injuries from a fall.
Caused by severe dizziness related to glycogen deficiency :D

Thank you all for your thoughtful and very helpful replies! You've given me a lot to chew on. :)

This document answers your question:
http://www.heartzones.com/_pdf/FatBurningwhitepaperreposted8305.pdf

Old document. I get a processing error with the latest Adobe reader, but it still works well enough.

Basically, I don't think it works that way, training-wise. Your body's not that smart. It does what it has to do to accomplish the task you give it. I believe the record for riding without eating or drinking is well over 200 miles, done by an extremely talented and trained individual.

It's called Bonk Training.

I don't do it, and I don't really suggest anyone else do it.

But some racers do it, and they say it works.

It's easy. Get up in the morning, ride your bike. Slowly increase
intensity/distance. Black coffee would be OK, but no calories, not even artificial sweetener.

I did try it, wasn't fun. I'm in it for the fun.I rode my first century today (165km in ~5:30) and only drank water during the ride. During the last hour I had trouble thinking of anything else other than food but I didn't bonk. I probably cheated though and ate a fairly big breakfast.

Do you mean Atkins? I thought that fad was long gone.

Did they ever determine his cause of death?

I think most people have an incorrect view of the Atkins diet. (thanks for the correction) If you read the book, it isn't about eating bacon and cheese for weight loss and it is not no carb, or even that low of carb intake, as long as you are loosing weight. You may also want to read the zone diet book, or the anabolic diet. All three speak of what the OP asked about.

Ride before breakfast =)

with this thread in mind, yesterday went out without eating breakfast and rode at 90+cadence and keeping heart rate in the fat burning zone which was in the 120s. What a tedious ride it was. It was like riding on a trainer, going nowhere fast. 50 miles that took forever.

with this thread in mind, yesterday went out without eating breakfast and rode at 90+cadence and keeping heart rate in the fat burning zone which was in the 120s. What a tedious ride it was. It was like riding on a trainer, going nowhere fast. 50 miles that took forever.

But just think how great it would be if you could do such an easy ride (http://connect.garmin.com/activity/39157456) and still go a decent speed?

But just think how great it would be if you could do such an easy ride (http://connect.garmin.com/activity/39157456) and still go a decent speed?

i dream of that.

by the way, is that a normal easy ride for you? i can't imagine you ride so gently for fat burning. there's nothing to burn!

i dream of that.

by the way, is that a normal easy ride for you? i can't imagine you ride so gently for fat burning. there's nothing to burn!

The goal wasn't fat burning, it was a recovery ride.

But just think how great it would be if you could do such an easy ride (http://connect.garmin.com/activity/39157456) and still go a decent speed?Hear, hear. That's what a good training program is supposed to produce. If you have an average VO2max, this is very attainable. So get after it!

Pat and Cranium have very good advice- keep chugging away with what they recommend, and you'll do better with your training.

As far as training your body to use fat as energy, that comes from lots and lots of base training. Simply put, base training is like building a foundation for your house- gives you a solid fitness base to work with later on in the season. Efficient base training will increase the amount and size of mitochondria, as well as increase the number of capillaries in the body, and help to thicken the heart and make it stronger. Fat is utilized as an energy source during aerobic respiration when the body is doing work. When fat is broken down in the mitochondria during respiration, your body produces ATP, the chemicals used for producing energy for the muscles. The more you produce, the more work you can do, and the more efficiently you can exercise. Better for you to work overall on base building and then putting together a good training program once you come out of base building.

But eating well, being efficient on the bike with good form, pacing, etc.... that'll get you through a ride and give you the best chance of getting a good overall fat burn that will sustain you throughout your training day.

koffee

Thanks everyone, I really appreciate your input. This is a fascinating topic and I'm trying to learn all I can so I can apply it to my own needs.

You can train your body to run on fat or a higher percentage of fat than carbs. Wear a heart rate monitor HRM and learn where your fat and carb burning zone overlaps and then stay in your fat burning zone to ride longer. To train your body to run on fat, there are two ways. 1) slow speed such as 10-12 mph, low HR only because a fast speed causes a high HR, high cadence which means riding in your easiest gears, cadence should be above 90 and preferably above 100 or even 120, then ride short distances such as 17 miles. As your body adapts and gets fit, you can ride longer distances at a faster speed. If your HR rises into the carb burning zone then you need to slow your speed, shift into an easier gear, or slow your cadence. When you start getting tired, your HR will rise and you'll move into the carb burning zone.

No matter what speed you ride at, you are always burning fat and carbs but the faster you go, the harder you press on the pedal, or the further you go, the more your HR will move into the carb burning zone. Eventually you will be able to ride faster and ride further with a lower HR.

Riding in the morning, before breakfast, only drink water, will burn fat and train your body to run on fat and then upon your return, eat protein and carbs such as eggs and toast.

You can train your body to run on fat or a higher percentage of fat than carbs. Wear a heart rate monitor HRM and learn where your fat and carb burning zone overlaps and then stay in your fat burning zone to ride longer. To train your body to run on fat, there are two ways. 1) slow speed such as 10-12 mph, low HR only because a fast speed causes a high HR, high cadence which means riding in your easiest gears, cadence should be above 90 and preferably above 100 or even 120, then ride short distances such as 17 miles. As your body adapts and gets fit, you can ride longer distances at a faster speed. If your HR rises into the carb burning zone then you need to slow your speed, shift into an easier gear, or slow your cadence. When you start getting tired, your HR will rise and you'll move into the carb burning zone.

No matter what speed you ride at, you are always burning fat and carbs but the faster you go, the harder you press on the pedal, or the further you go, the more your HR will move into the carb burning zone. Eventually you will be able to ride faster and ride further with a lower HR.

Riding in the morning, before breakfast, only drink water, will burn fat and train your body to run on fat and then upon your return, eat protein and carbs such as eggs and toast.

There is a lot of half and mis-information in there, and a lot of this has already been covered in the thread.

There is a lot of half and mis-information in there, and a lot of this has already been covered in the thread.

+1

koffee

Ketogenic diet...

Doesn't your body always burn a certain percentage of fat? As the saying goes... "fat burns in a carbohydrate flame"

The basic answer is you starve yourself... really, there is no training of evolution/lipid metabolism unless you're going for gene therapy.

Good luck with starving yourself. It rarely works unless you're an alcoholic or have OCD, for one your metabolism will store every single calorie it can as fat as soon as it realizes what is up. Pretty stupid if you ask me, I hope you reconsider your goals and are able to be satisfied with whatever gains you can get through normal, healthy hard-work and a balanced diet.

P.S. You'll know when you're ketonic from lack of carbs when your breath smells like a garbage dump, your liver starts to fail and your heart weakens. RIP Atkins.

Insuline aka carbs leads to a decrease in fat consumption for energy since sugars in the blood increase. If you want to burn more fat during your workouts don't eat during them. If your goal is weight loss then not eating during rides is best because it helps to keep a negative energy balance. If your goal is an increase in overall fitness continue eating during your rides.

+1

If you want to burn a higher percentage of fat you need to ride easier. The harder you ride the faster you'll burn through your limited (around 2000 Cals) Glycogen stores. As you gain fitness you will naturally use less glycogen and more fat at a given power output.

How hard are you riding on your long rides? Are you working close to your threshold? Experiment a little and try leaving the clif bar in your pocket and seeing how far you get before you need to eat. Drink coffee only at the breakfast stop. If you are riding at a moderate pace you should be able to get through 40 miles without any food. I wouldn't normally eat unless I'm riding hard for 3+ hrs.

The fatburning zone is a bunch of crap! In this zone you burn a greater percentage of fat compared to carbs, but if you increase your intensity and do inverval training you will burn a larger amount of carbs to fat ratio, but you will also burn more fat overall. People don't just burn through their stores of 2000 calories that easily in a workout and low exercise levels over a prolongued time have never been the answer to shedding fat.

Either diet has to be fairly strict, exercise program has to be intense, or a combination of both works well. There is no shortcut to getting into good shape. Only hard work and consistancy are the key.

The fatburning zone is a bunch of crap! In this zone you burn a greater percentage of fat compared to carbs, but if you increase your intensity and do inverval training you will burn a larger amount of carbs to fat ratio, but you will also burn more fat overall. People don't just burn through their stores of 2000 calories that easily in a workout and low exercise levels over a prolongued time have never been the answer to shedding fat.I think you are agreeing with me. If you ride at a high intensity level you can burn through 2000 Calories of glycogen in a couple of hours. Ride at a lower intensity and you can ride longer and burn more calories.

Intervals are great for riding faster but they aren't optimal for losing weight. High intensity training also increases appetite.

I think you are agreeing with me. If you ride at a high intensity level you can burn through 2000 Calories of glycogen in a couple of hours. Ride at a lower intensity and you can ride longer and burn more calories.

Intervals are great for riding faster but they aren't optimal for losing weight. High intensity training also increases appetite.

Exactly. I can go out and ride 100 miles in 6 hours on water, get home, have a light lunch, some snacks and then dinner. Maybe consume 3000 cal for the day, but burned well over 3000 cal on the ride, with a very low % of carbs. If I go out and ride hard for 3 hours with intervals (or say, a race), I'll burn still a substantial amount (say, 800 cal/hr vs 500-600), but I will have eaten on the ride, had a recovery shake after, and still be ravenous the rest of the day.

Exactly. I can go out and ride 100 miles in 6 hours on water, get home, have a light lunch, some snacks and then dinner. Maybe consume 3000 cal for the day, but burned well over 3000 cal on the ride, with a very low % of carbs. If I go out and ride hard for 3 hours with intervals (or say, a race), I'll burn still a substantial amount (say, 800 cal/hr vs 500-600), but I will have eaten on the ride, had a recovery shake after, and still be ravenous the rest of the day.


Hmm high intensity exercise has been proven to burn fat better than regular steady state training which is why so many exercise programs are based off of it. Examples, PX 90 has a lot of high intensity cardio, so does Insanity (a new exercise program based off of high intensity bursts of plyometric exercises for a greater duration of exertion than at the lower levels of exercise followed by very few seconds of low intensity exercise), Tae Bo also had a lot of high intensity bursts to help burn more fat and overall calories in their workouts. The same tactics are used on the biggest loser which is why you see 400 lb people running on treadmills rather than walking on them for hours at a time.

As for riding 100 miles with just water, I could only imagine how much muscle is lost during one of those rides with no food replenishment.

I think you are agreeing with me. If you ride at a high intensity level you can burn through 2000 Calories of glycogen in a couple of hours. Ride at a lower intensity and you can ride longer and burn more calories.

Intervals are great for riding faster but they aren't optimal for losing weight. High intensity training also increases appetite.

I am not agreeing with you. If you are running out of glygen stores before you are spent during exercise you are not riding at a high enough intensity IMO. If you have ever tried to do a program that it was so intense that after 10-15 mintues you were dripping with sweat I would say you are doing high intensity exercise. If you are exercising for a few hours on end you are not riding intense in the fitness world. I'll take any rider who can "ride intensly for hours" and in less than 15 mintues I put them to their knees due to an intense workout.

Hmm high intensity exercise has been proven to burn fat better than regular steady state training which is why so many exercise programs are based off of it. Examples, PX 90 has a lot of high intensity cardio, so does Intensity (a new exercise program based off of plyometrics), Tae Bo also had a lot of high intensity bursts to help burn more fat and overall calories in their workouts. The same tactics are used on the biggest loser which is why you see 400 lb people running on treadmills rather than walking on them for hours at a time.

IF you can control your appetite, obviously high intensity will burn more calories and more fat than lower intensity. But it spikes your appetite, your body wants to replace all those carbs that it lost. If you go longer at a lower intensity (I said lower not walking btw, so nice strawman there) your body is burning mostly fat (which, hey, is the question actually being asked!), which your body is not as anxious to try to recover by making you hungry. A recovery drink after to replenish and top off, and then continue the day with fairly regular eating. High intensity is like afterburner, you need to dump fuel directly into the fire to keep it going and your body will crave for it to be restored when it is done. Those biggest looser people practically starve themselves on top of all that exercise and many of them rebound after.


As for riding 100 miles with just water, I could only imagine how much muscle is lost during one of those rides with no food replenishment.

You can imagine all you want, but it's trivial enough for me that I can do it on what I have stored plus what I ate beforehand and recover with after. I only really do it in the winter when I am [relatively] fat anyway, so lots of fat stores to burn through.

I am not agreeing with you. If you are running out of glygen stores before you are spent during exercise you are not riding at a high enough intensity IMO. If you have ever tried to do a program that it was so intense that after 10-15 mintues you were dripping with sweat I would say you are doing high intensity exercise. If you are exercising for a few hours on end you are not riding intense in the fitness world. I'll take any rider who can "ride intensly for hours" and in less than 15 mintues I put them to their knees due to an intense workout.

This says all I need to hear to fully understand that you have no idea what the F you are talking about...

No, I know what I am talking about, I have spent countless hours studying exercise. Believe what you want. The information I have been provided is from scientific evidence, not broscience.

You're trying to argue semantics. Intensity is going to be relative and depend on what you are doing. I assure you those of us who race know how to ride with intensity. Go do a road race and try to ride off the front and tell me that's not intense. Or intervals. Threshold, vow, tabatas, etc. Sets of 40-20s that will make you want to puke.

http://www.youtube.com/watch?v=ulPnlyWURz4&feature=related

http://www.youtube.com/watch?v=haSljTB1wZM

The first video is of a nutritionist/ personal trainer who knows a lot about exercise and diet as I've seen through his videos. The second video was created by a highly respected member who writes a columb for mens health magazine.

How does that contradict anything I said?

Doesn't your body always burn a certain percentage of fat? As the saying goes... "fat burns in a carbohydrate flame"

Yes, fat, carbs and protein are burnt ALL the time. Different heartrates and exertion levels just change the ratios. Carbs and fat are the two primary fuels of choice with the proteins always adding a little to the mix (not to mention a couple other sources of fuel the body will use in a pinch).

Also, it's "Fat burns in a PROTEIN fire". Sort of a misnomer though as it's actually a "fat fire", and it needs a little extra protein to process. That's why it's important to take in protein during exercise, and AFTER exercise. If the body needs protein to process fat, but there isn't enough in your system, it either reduces fat processing or takes the protein from muscles and organs. If you worked hard, and some muscle repair is needed, then there's ANOTHER thing the body need protein for aside from processing fat for fuel.

Fat takes a lot of oxygen to turn into fuel, as mentioned, along with a little protein. Until the metabolism starts to stabilize after starting an exercise session, that's why it takes a while (5 to 20 or even 30 minutes, depending on the individual), even at low heart rates, to switch over to more fat and fewer carbs being burned. Once all the chemical processes are stabilized, and the oxygen builds up in the blood, then the body starts processing more fat.

The amount of oxygen required to burn fat is also why it is encouraged to do intervals. Doesn't matter than a person isn't looking to race or be a sprinter. Intervals make the body react by increasing hemoglobin production, which means there is more oxygen available. More oxygen availability means not only will the body start processing fat sooner, but it will be able to process fat at higher heartrates and efforts too.

The higher the heart rate and effort are, the faster the body is buring through fuel. If the fuel is being burnt faster than the body can process fat and protein, it makes up for the defecit by burning carbs. Carbs have less energy content than either fat or protein, but carbs are easier and faster to turn into fuel. If you do intervals, and increase the oxygen carrying capacity of your blood, that means there is enough "extra" oxygen (oxygen not being needed by the muscles) that the body can continue burning fat for fuel. As exertion levels increase, and more oxygen is needed for the muscles, less and less fat will be converted, and more carbs will be used. Even at rest, muscles need resources. The more muscle mass, the more energy you burn, even at rest. With low heartrates, and enough oxygen and protein, the body will burn fat then too.

The fact that protein is burnt to process fat, is one aspect of the "protein diet" concept. Not being a fanboy of it, but the basic idea is that a low carb, high protein diet helps burn extra fat. The body use a lot of energy to process protein. The fact that carb intake is kept low, means that the body will use some of the proteins to burn with fat, to produce the energy, to process the rest of the protein. Again, not preaching, just that the concept ties in with the whole "fat thing".

So, you can't "train" a body to use fat, but you CAN change the way you train so that you set the body up to use predominantly fat as a fuel. This is a very simplified explanation of what is going on, but it might help.

I want to just add that eating protein on a bicycle is not required unless you're engaging in a ride over say... 90mins. From what i recall that protein you eat isn't even available to "burn fat" for a while. You however should be eating protein in your recovery, which is why stopping by a convenience store and downing some cold chocolate milk a few minutes after the ride tastes great!