No Bonking Here

[gbs]

When planning a ride should I assume

• 25kph rolling average means about 550Kcals/hr of energy output
• max rate of ingestion/input is about 350Kcals/hr
• glycogen bank is about 1200Kcals
• bonking occurs when glycogen is depleted - say 6 hours on the above assumptions?

The max rate of ingestion asssumption is particularly open to comment please.

I know that there are a huge numberof variables that will affect these assumptions and conclusion but nonetheless a rough and ready calculation seems useful to me.

 

[Greenbank]

When planning a ride should I assume

• 25kph rolling average means about 550Kcals/hr of energy output
• max rate of ingestion/input is about 350Kcals/hr
• glycogen bank is about 1200Kcals
• bonking occurs when glycogen is depleted - say 6 hours on the above assumptions?

The max rate of ingestion asssumption is particularly open to comment please.

I know that there are a huge numberof variables that will affect these assumptions and conclusion but nonetheless a rough and ready calculation seems useful to me.

Not all of your calories expended need come from your calorie intake.

As the saying goes: "Fat burns in a carbohydrate flame". At low intensity (cruising on the flat) you could be burning 50% fat and 50% carbs. At this lower intensity, say 400kcal an hour, you'll be getting 200kcal of that energy from your fat stores and 200kcal from blood sugar, which is easily replaced by eating (since you can ingest ~350kcal an hour).

The faster you go the more inefficient your body gets at using fats, since it just can't metabolise it into energy fast enough, so it uses more glycogen.

So at 550kcal an hour (25kph rolling) it might be 70% CHO and only 30% fat. 70% of 550kcal is 385kcal, which is just above that 350kcal ingestion figure, but 1200/35 = 34 hours that you should be able to keep that up. (based on those figures).

Obviously the CHO:fat burn ratio will differ for individuals, and also even during a ride as the body's physiology changes. There's no magic formula.

I've done a 200km Audax (in just over 13 hours elapsed) without eating during the ride (and no breakfast, the last food was some 8 hours before I started). That's close to ~5000kcal expended with 0 intake.

Just eat little and often whilst moving and stop for a larger feed (cafe or petrol station) along the way. I did 1400km of London-Edinburgh-London in 116 hours with meals every 4-6 hours or so. Nom nom nom.

 

[Banjo]

Not all of your calories expended need come from your calorie intake.

As the saying goes: "Fat burns in a carbohydrate flame". At low intensity (cruising on the flat) you could be burning 50% fat and 50% carbs. At this lower intensity, say 400kcal an hour, you'll be getting 200kcal of that energy from your fat stores and 200kcal from blood sugar, which is easily replaced by eating (since you can ingest ~350kcal an hour).

The faster you go the more inefficient your body gets at using fats, since it just can't metabolise it into energy fast enough, so it uses more glycogen.

So at 550kcal an hour (25kph rolling) it might be 70% CHO and only 30% fat. 70% of 550kcal is 385kcal, which is just above that 350kcal ingestion figure, but 1200/35 = 34 hours that you should be able to keep that up. (based on those figures).

Obviously the CHO:fat burn ratio will differ for individuals, and also even during a ride as the body's physiology changes. There's no magic formula.

I've done a 200km Audax (in just over 13 hours elapsed) without eating during the ride (and no breakfast, the last food was some 8 hours before I started). That's close to ~5000kcal expended with 0 intake.

Just eat little and often whilst moving and stop for a larger feed (cafe or petrol station) along the way. I did 1400km of London-Edinburgh-London in 116 hours with meals every 4-6 hours or so. Nom nom nom.

Why did you do a 200 on empty? was it an experiment of some kind. I think I could do a 100 on no intake but defo not a 200.

Jelly Babies are conveniently 10 calories each

 

[Greenbank]

As a weight loss ride. I knew my fat metabolism was pretty efficient, as I was fit enough to go along at a reasonable pace but keeping my HR relatively low.

 

[BrumJim]

I recommend that you don't turn the calories burnt into weight loss. It'll be a shock as to how little it is.

Recommend instead a programme of continual exercise, combined with calorie input rationalisation - i.e. not increasing food input to take account of more exercise, cutting out or drastically reducing some of the higher fat inputs, and making a more regular change in diet - e.g. more salad rather than chips, post-pub kebab rarely, rather than as a habit, and 50 mile rides every weekend, with midweek rides where possible.

 

[Zinthar]

The faster you go the more inefficient your body gets at using fats, since it just can't metabolise it into energy fast enough, so it uses more glycogen.

That's very interesting to me...I've been trying to lose weight by cycling and I have been trying to keep the speed up for longer distances and I'm not losing hardly anything. Are you saying that I should slow down and go longer distances for weight loss?

BTW, I've found that taking 2 chewable glucose tablets immediately prior to the ride really gives me a boost of energy at the start.

 

[italiafirenze]

That's very interesting to me...I've been trying to lose weight by cycling and I have been trying to keep the speed up for longer distances and I'm not losing hardly anything. Are you saying that I should slow down and go longer distances for weight loss?

BTW, I've found that taking 2 chewable glucose tablets immediately prior to the ride really gives me a boost of energy at the start.

What he means is after a certain point your body can't get ALL the energy it needs from fats (it's preferred fuel source) so it has to look to glycogen and protein.

At a low intensity your body will use a certain amount of energy per hour (say 200kj), that energy will be derived mostly from fat because the amounts of energy required are slight and your body is capable of using only it's preferred fuel source, fat.

At high intensity your body will use more energy per hour (say 500kj), at some point between 200kj and 500kj your body will no longer be able to use only it's preferred fuel source (fat) and will need to supplement that fuel source with glycogen from the muscles and liver.

So, the harder you go the more fat you will burn, no matter what. The key is finding the point at which you can go very hard for a prolonged period of time. Hence interval training and so forth. It's no coincidence that professional athletes are also very lean, it's from high intensity not very slow rides around the countryside.

 

[Greenbank]

What he means is after a certain point your body can't get ALL the energy it needs from fats (it's preferred fuel source) so it has to look to glycogen and protein.

At best it is 50:50 for any level of exercise that's worthwhile maintaining.

To answer the previous question of whether it's best to do long slow distance or speed work for weight loss, the answer is: no-one is entirely sure.

Some studies (google: HIIT weight loss) have shown that shorter high intensity workouts can have just as good a weight loss outcome as long slow distance, but it depends on lots of other things, such as being in strict control over what you eat before/during/after the exercise. With high intensity work it's much easier to deplete ones glycogen stores without making much of an impact on the fat store, and then pigging out on food to replace the depleted glycogen leaving you worse off than you were before.

My only advice would be to concentrate more on calorie intake, and knowing exactly what you are eating, than worrying about whether the intensity of the exercise you're performing is too high/low. Avoid the trap of doing lots of good exercise but over-compensating with food after the fact.

 

[Fiona N]

To answer the previous question of whether it's best to do long slow distance or speed work for weight loss, the answer is: no-one is entirely sure.

Not so much 'no one is really sure' as 'it depends on the individual'. For example, back in the late '80s when I was tested, it was found that I could use >80% fat at low aerobic efforts (50-60% HRM) and that this rate dropped off quite slowly so that I still hard a significant proportion of fat burning at HRs (80-90% HRM) where preponderance of glycogen use was expected. I seem to recall that we worked out that my maximum fat burn per hour was at about 75-80% HRM as the work rate was so much higher that the total fat burn was greater than at low work rates where the fat % was greater. For someone whose fat burning drops off much quicker with HR, it makes more sense to stick with lower work rates. But those 'fat burning zones' marked on gym machines seem to be way too low for most people - if you're working at <200 kcal/hr (strolling pace) even 100% fat burning isn't getting you anywhere.

 

[italiafirenze]

My only advice would be to concentrate more on calorie intake, and knowing exactly what you are eating, than worrying about whether the intensity of the exercise you're performing is too high/low. Avoid the trap of doing lots of good exercise but over-compensating with food after the fact.

I think that's the best advice there is. Of course the only way to lose weight is to burn more than you consume. It's easy to fall into the trap of eating more because of the hunger the exercise produces.

 

[ColinJ]

I recommend that you don't turn the calories burnt into weight loss. It'll be a shock as to how little it is.

Hmm - it's obviously a lot harder to burn fat off than it is to just avoid the fat-producing calories in the first place, but I consistently lose about 1/100th of a pound a mile when riding moderately hard. I obviously don't measure it a mile at a time, but I've done lots of 100 mile sportives and 200 km audax rides and I lose about 1.0 pounds on a century and 1.25 pounds on a 200 (125 miles). That's despite the extra calories I take on board during and after those longish rides. (I usually save on post-ride alcohol calories because I tend to fall asleep before I can drink them! )

 

[yello]

I recommend that you don't turn the calories burnt into weight loss.

I find that statement really both interesting and intriguing. It leads me to some favourite thought areas.

I think (but have no idea in truth) that the relationship between calories and weight is more complex than we might believe. I don't think weight loss is quite as simple as 'burn more than you eat'. At it's most basic, yes it's a good rule of thumb, but I do think there is more involved than that.

There is no shortage of people that are really trying to loose weight by calorie counting but it's just not happening for them (and, yes, some are not being honest about what they eat). I suspect the individual's body chemistry (or whatever) has to be considered, as does the nature of the calorie. All calories are not equal perhaps?

Added to that, I've always been interested in WHEN we loose weight. For example, my weight after a ride is pretty much the same as before it - allowing for dehydration. But it's on the ride that I burn the calories, so burning calories wouldn't appear to lead to immediate weight loss. It's the following morning that I'll see any weight loss... yet if there's any time of day that my rate of calorie burn is at it's lowest then wouldn't it be when I'm inactive, i.e. asleep? Unless, of course, I'm a sleep marathon runner!

 

[Greenbank]

I find that statement really both interesting and intriguing. It leads me to some favourite thought areas.

I think (but have no idea in truth) that the relationship between calories and weight is more complex than we might believe. I don't think weight loss is quite as simple as 'burn more than you eat'. At it's most basic, yes it's a good rule of thumb, but I do think there is more involved than that.

Indeed. At higher and higher intensities you burn more glycogen than fat.

Taken from http://www.ultracycling.com/nutrition/calories.html :-

"Approximate Sources of Energy While Riding

% of VO2 = max CHO/Fat
20-50% = about 50/50
60% = about 60/40
70% = about 70/30
80% = about 80/20
90% = 90-100% CHO. "

So if I burn ~2500kcal at 80% VO[sub]2[/sub] max (a nice hard 3 hour ride pushing myself), 2000kcal of that will come from glycogen/protein and only 500kcal from fat stores.

To replace the 2000kcal in my glycogen stores I'll need to eat, it can't be replaced by my body metabolising fat. So that only leaves me with a potential of 500kcal worth of weight loss, which is a seventh of a pound or 64g (1lb of fat is 3500kcal). And that's only if the 2000kcal I've eaten is mainly carbs, if some of it is fats then that complicates it further. The glycogen 'buffer' is why calories in vs calories out doesn't really work very well.

Alternatively, 3 hours of nice paced cycling may only be 400kcal an hour to give 1200kcal total. But 50% of the energy from that comes from fat, or 600kcal. More than the 500kcal from fat from 3 hours of pushing much harder.

Obviously this is just all inferred from example numbers, but you get the idea.

 

[italiafirenze]

There is no shortage of people that are really trying to loose weight by calorie counting but it's just not happening for them (and, yes, some are not being honest about what they eat). I suspect the individual's body chemistry (or whatever) has to be considered, as does the nature of the calorie. All calories are not equal perhaps?

I think it is a lot simpler than a lot of people want to make it out to be. There is no doubting the science on this. Just look at the 39 stone cycling guy. That is someone really trying to lose weight and he should be held up as an example to others. Too many overweight people think they deserve overnight results for cutting a donut or two out of their diet. But it doesn't happen like that. Hard work and less food = lose weight. If it isn't working, you're not doing one or the other enough.

Obviously this is just all inferred from example numbers, but you get the idea.

Unfortunately I think that your inferred numbers give the wrong idea. Whilst the science seems to support such an idea some of the numbers you have used do seem a bit confusing. Yes the 50/50 - 80/20 percentages seem to be roughly accurate according to the information you linked to; but I think you've interpreted them in the wrong way.



I think the big problem is that too many people are confusing what intensities are being referred to when talking about the energy systems the body is using; I fear you may have looked at the tables without reading the article.


The crucial sentence from the website you linked is here;


"At exercise intensities below the lactate threshold (LT), fat and carbohydrates provide approximately equal amounts of energy, and above LT the major energy source is carbohydrate."


Now from the same website we have; "An important criterion is where LT falls for a given individual. For many people it's at 60-70% max, but can range up to over 80% of VO2 max for very fit individuals." From this we can infer that LT falls anywhere between 60-85% from average to absolute elite athlete.


Taking this into account, most people cannot ride above 80% VO2max for the three hours in your example, they'd be lucky to achieve it for three minutes. Lactate threshold limits the amount of work your muscles can complete and so above it you can work for only very short periods (from seconds to minutes, not hours).
So unless you are an elite rider or ex-pro the figures in your example (the mix of fuel) are mis-representative; and if even you are, they don't apply to 99% of people here.


Given this we can see that the difference between a "hard" ride and an "easy" ride over a length of 3 hours would be very little in terms of CHO/Fat proportion but the harder ride would be higher in terms of total work done and so calories burned.


I don't have the accurate figures for calories over my last few rides on this computer to give examples between intensities unfortunately and I am not keen to simply guess at them.


Yes, the science says that at higher intensity the body is using all carbs to fuel. But it means intensities that most cyclists (non-elite) can keep up for a few minutes at best. At any sort of intensity you can maintain for hours on end (sub-lactate threshold), it's a mixture of fat and carbs (roughly 50/50) and you will burn proportionately more fat for going hard over the same time frame than you will by not.


So if you want to lose weight, go harder, not softer; make yourself suffer.


It would be nice for the 39 stone cyclist to weigh in here (wahey!) as he is a real world example.

 

[Zinthar]

It would be nice for the 39 stone cyclist to weigh in here (wahey!) as he is a real world example.

Nice!!!