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Dave Smith on why riding in the 'fat burning zone' is a waste of time if you want a slimmer waist

A couple of weeks ago I’d have worn out the batteries in my Face Palmer if I had one. Another online article that on face value appeared to make perfect sense, referencing a research paper no less, related to ‘fat-burning’ rides. The reality however was that the interpretation was erroneous, condemning numerous cyclists to riding along at 14 mph to ‘burn fat’.

The only thing that grates with me more than the use or even consideration of the use of the term ‘anaerobic threshold’, is the utter confusion that surrounds the term ‘fat-burning zone’. It’s understandable given the terms adoption by the fitness industry, but let me tell you a little secret. The fitness industry embraces the fat burning zones on their cardio equipment to help the unfit think they’ve done a valuable workout. I know this as a director of one of the world’s largest fitness equipment manufacturers said it to me. He conceded that ‘fat burning zones’ had little real value, but stated that “most people who go to a gym don’t want a strenuous workout”.

But back to bikes

The first issue with fat burning zone, is that it exists. There is certainly a level of intensity at which fat contributes a greater proportion of energy to fuel exercise. The level of intensity varies from one individual to another and also within one individual from day to day, based on training status and nutritional inputs.

For example, if you wake up and exercise in a fasted state, you’ll burn more fat and at higher intensities than after a carbohydrate breakfast.

So what’s my problem?

Quite simply, this fat burning zone is something you should pretty much ignore if you wish to lose body fat. That’s a prime example of those sneaky counterintuitive things. There are several reasons to eschew the slow plodding rides that will have you favouring fat over carbs as fuel.

The first is that you’ll burn very little body fat in the first place. One gram of fat is worth 9 calories. Since ‘fat-burning zone’ exercise burns roughly 140 to 180 calories in 30 minutes, with an estimate of 50 to 60 percent of those calories coming from fat it translates 8 to 12g of fat in 30 minutes - or two times that amount in an hour.

Good luck losing that stone. 

The second reason to avoid long slow training sessions is that they increase appetite, whilst high intensity intervals suppress appetite. So you may have done 3 hours and burned 60 grams of fat (whoop) but you’re more likely to reach for the tub of ice cream afterwards.

An interval session will have a greater calorie cost when recovery metabolism is included, and also suppresses hunger. Whilst losing body fat is not a simple case of ‘calories in calories out’, calories do play some part in waist management.

You don’t believe me, do you?

Boffins at Laval University in Quebec* had two groups participate in different exercise sessions. Seventeen subjects trained on an indoor bike four to five times per week for 20 weeks, with workouts lasting from 30 to 45 minutes and exercise intensity ranged from 60-85 per cent of maximal heart rate.



A second group of 10 subjects completed 30-minute workouts at an intensity comparable to that attained by the first group. However, the second group also conducted 19 short and 16 long interval sessions during their 15-week programme. The short-interval sessions consisted of 10 to 15 intervals lasting for 15-30 seconds, while the long-interval efforts were composed of four to five intervals with durations of 60-90 seconds.Total energy expenditure during training was twice as great in the first group as in the second group – they burned more calories. However, each group achieved about a 30% increase in maximal aerobic capacity. Most surprisingly however, the interval-trained athletes (who performed less total work remember) had a 9x greater loss of body fat than the first group.

This research was done more than 20 years ago, yet the misconception still exists that low intensity exercise in your ‘fat burning zone’ is best for losing body fat, hence my palming of the face last week.

Still not convinced? Try to recall the 100m final at the Olympics - men and women. What do the fastest men and women on earth look like? They’re not the fattest athletes on display are they? In fact, I suspect they have less body fat than marathon runners yet how much training time do you think they spend in their ‘fat-burning zones’?

So what should you do to lose body fat? Firstly, forget about your fat burning zone. And I hate to break it to you but ‘eat less, exercise more’ only has a 5% long-term success rate. It’s also not all about calories as we’re not a sealed unit where calories in and calories out have a great relevance – we have hormones and feedback loops and all kinds of bat-shit crazy things going under the skin.

The simple answer is to choose food and exercise that will control your appetite and hunger effectively, avoid switching on the sugar fuelled ovens in the body when you start the day, and focus on high intensity interval training. Choose foods that don’t encourage the storage of body fat, which in practical terms means that unless you’re exercising hard, set aside the sugar for the builder’s tea.

Oh, and lift heavy things. Make your muscle work hard regularly.

Now the bit where I contradict myself - it’s not all a big downer on exercising to become more efficient at burning fat. It does have an important role to play for enhancing endurance performance in longer events, preserving glycogen and allowing you to plod on without pockets and bottles full of sugar.

To become better at fat burning, ride in a fasted state and ride long. Don’t fuel up on cereals and gels before a sportive - that will switch your fat burning off. Do all of this and keep riding when you feel empty to force your muscle to make powerful adaptations - turning you into an efficient fat burning machine that will drag your bike though the darkness of a 600km audax, or the last hour of the Dragon Ride.

Just don’t do it to lose weight**. Please.

* 'lmpact of Exercise Intensity on Body Fatness and Skeletal Muscle Metabolism, ' Metabolism, vol. 43(7), pp 814-818, 1994)

**Although you will lose some weight.

Dave Smith has been involved in coaching cyclists in all disciplines for more than 25 years. A former GB national and Olympic road coach, Dave has trained Tour stage winners and Olympic medallists, world champions and numerous national champions. In addition he has applied his quirky and counter intuitive thinking to help dozens of regular cyclists, polo players and F1 drivers. He rides 250 miles a week on and off-road in all weathers.

120 comments

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mzungu [40 posts] 3 years ago
0 likes

Hmm, interesting...

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glynr36 [637 posts] 3 years ago
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Makes sense really, how many mamils do you see out on a weekend and a sedentary pace then stuffing their faces at the cafe, and they're still bulging out of lycra!

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McDuff73 [79 posts] 3 years ago
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find out what works best for your needs

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Grizzerly [369 posts] 3 years ago
1 like

Compare 100m runner with marathon runners. 100m runners have less body fat than marathon runners? Which events have you been watching? All the serious marathon runners I've ever seen look like anorexic skeletons, many 100m runners are positively chunky.

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SamSkjord [39 posts] 3 years ago
2 likes

All of the this.

Also, no, you do not hurt because of lactic acid, nor have you ever produced any unless you're a biochemist.

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crikey [1251 posts] 3 years ago
9 likes

Unfortunately the majority of cyclists these days get their 'wisdom' from the internet which means that poor information gets passed on from person to person very quickly.
Hence the 'average' cyclist thinks that any kind of cycling requires gels and bars and energy drinks, then a recovery drink to finish off, even though the actual calorie expenditure is far less than the total of rubbish they think they 'have' to consume.

See also those people who simply cannot ride for an hour without drinking at least a litre of fluid, and those who think that they have to 'replace those electrolytes'...

The Sports Nutrition industry, and it is an industry, have been telling and selling you rubbish for years...

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curdins [60 posts] 3 years ago
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Dave - you're a genius, or mad - or peperhaps a bit of both. You mean to be fitter, leaner and faster, I should do intensity? What about the 'base of the pyramid', the long miles that give you the conditioning required to avoid injury from these intense efforts? I'm convinced they're required, but are you saying throw intervals in now when I don't feel particularly 'trained'?

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mzungu [40 posts] 3 years ago
1 like

To add to my previous comment, its quite nice to see I can do something with the time I have.

It's easier to fit intervals in a working day than a half marathon on a lunchbreak...

Guess there are no more excuses...

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tomturcan [66 posts] 3 years ago
1 like

Useful article, very plausible. A question - I heard someone say that in high intensity exercise if your glycogen is used up, your body will metabolise muscle rather than fat, undermining all that effort to build the muscle in the first place. So is that true, for those fat-burning pre-breakfast rides do you need to keep the intensity down?

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Dave Smith [47 posts] 3 years ago
6 likes

Grizzerly, you're referring to body size in sprinters vs marathon runners, not body fat levels. Two completely different things.

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Dave Smith [47 posts] 3 years ago
1 like

The article, with the suggestion to avoid long slow miles, is in the context of reducing body fat levels. There will be situations where steady miles could play an important part in a cyclists training plan, but weight loss isn't one of them.

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FluffyKittenofT... [2088 posts] 3 years ago
1 like
crikey wrote:

Unfortunately the majority of cyclists these days get their 'wisdom' from the internet which means that poor information gets passed on from person to person very quickly.
Hence the 'average' cyclist thinks that any kind of cycling requires gels and bars and energy drinks, then a recovery drink to finish off, even though the actual calorie expenditure is far less than the total of rubbish they think they 'have' to consume.

See also those people who simply cannot ride for an hour without drinking at least a litre of fluid, and those who think that they have to 'replace those electrolytes'...

The Sports Nutrition industry, and it is an industry, have been telling and selling you rubbish for years...

Nobody who rides a bike that I know of worries about 'gels' or 'recovery drinks'.
Perhaps the belief that lots of people do is itself one of those internet-propagated myths?

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edster99 [340 posts] 3 years ago
1 like
FluffyKittenofTindalos wrote:
crikey wrote:

Unfortunately the majority of cyclists these days get their 'wisdom' from the internet which means that poor information gets passed on from person to person very quickly.
Hence the 'average' cyclist thinks that any kind of cycling requires gels and bars and energy drinks, then a recovery drink to finish off, even though the actual calorie expenditure is far less than the total of rubbish they think they 'have' to consume.

See also those people who simply cannot ride for an hour without drinking at least a litre of fluid, and those who think that they have to 'replace those electrolytes'...

The Sports Nutrition industry, and it is an industry, have been telling and selling you rubbish for years...

Nobody who rides a bike that I know of worries about 'gels' or 'recovery drinks'.
Perhaps the belief that lots of people do is itself one of those internet-propagated myths?

I did neck gels when I started. Now, I do carry a couple of gels in case of emergencies but they last a long, long time. Recovery drinks - generally after weight training, it seems to reduce muscle soreness, but perhaps thats a placebo. I could beleive it...

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jonnycondor [12 posts] 3 years ago
1 like

Kind of agree.... Big problem I find is if I do hard muscular top end rides now, by April iv hit my Peak race form, by August my legs are heavy and by September I need a break. And as for appetite, ypu wouldn't want to have seen me after riding 134 miles at events this summer, I woke up twice in the night to eat!
I'm doing zone 1-2 training to minimise muscle damage, get into a meditative zone and learn to be humble when the uni boys at Brookes come screaming by in a chaingang.

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OnTheRopes [181 posts] 3 years ago
1 like

I wouldn't have thought fasting on a sportive was a great idea. Sportives are for getting round and if your overweight on the day I would suggest its a bit late for worrying about losing weight until after the event. But I appreciate the intent

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Grizzerly [369 posts] 3 years ago
0 likes

It all comes down to simple arithmetic. Fuel input > work output = body fat increase, fuel input < work output = body fat decrease. How you time your work output or how you concentrate it has no bearing on the process whatsoever. People keep reinventing the same ideas over and over again, but it doesn't change the basic equation.
I recall having the conversation about 'bonk riding' before breakfast, way back in the 1970s. The idea had had periods of popularity in every decade back to the 1920s and had always been found to be ineffective.
Sorry guys, there are no short cuts to losing weight. The only thing that works is:
Eat less and exercise more.

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Grizzerly [369 posts] 3 years ago
0 likes

Velocity & vitality, if you compare the muscle definition of sprinters and distance runners, it is pretty clear that distance runners, generally, have lower body fat levels than sprinters, body SHAPE has little to do with body fat.

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Dave Smith [47 posts] 3 years ago
4 likes

"Sorry guys, there are no short cuts to losing weight. The only thing that works is: Eat less and exercise more."

This has < 5% success rate

Would you fly with an airline that only arrived at it's destination 5% of the time?

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Tintow [44 posts] 3 years ago
0 likes
Dave Smith wrote:

"Sorry guys, there are no short cuts to losing weight. The only thing that works is: Eat less and exercise more."

This has < 5% success rate

Would you fly with an airline that only arrived at it's destination 5% of the time?

Sorry Dave but this has been supported by numerous medical surveys - not sure what this has got to do with airlines but would you care to point out your evidence that people eating less and exercising more lose weight less than 5% of the time.

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Dave Smith [47 posts] 3 years ago
6 likes

People who try to 'eat less and exercise more' fail to achieve long term success 95% of the time. This is why there is a diet industry - if this worked they'd never get repeat business. It's a method that results in initial weight-loss in the very few able to maintain such a restrictive and hunger dominated lifestyle. Long term it fails.

That's the basis for saying it doesn't 'work'. It's just not a successful method and classically results in yo-yo fat % - the rhythm method of girth control.

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Tintow [44 posts] 3 years ago
0 likes

Ok, apologies Dave - my bad - I didn't realise you were quoting the article, I read that as an original point.
Out of interest, if eating less and exercising more isn't the solution - what is?

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Yennings [237 posts] 3 years ago
0 likes

Some good points here. People are generally too quick to accept the received wisdom and pseudoscience of the day, not to mention the marketing bullshit of the Big Pharma companies that increasingly control the commercial sports nutrition market.

That said, is it not true that in broad terms, most people can only store around 90 mins worth of glycogen in their muscles/liver/bloodstream? So surely simple logic thus dictates that anyone riding steadily for more than 1h30 without topping up their glycogen supplies with drinks, gels or any of that goop, will inevitably start to burn a higher proportion of their fat supplies as the glycogen tank becomes emptier?

Fire away as I'm quite interested in sports nutrition and would love to be proven wrong/re-educated here...

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FlatericFan [29 posts] 3 years ago
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Fat will only burn with a mix of Carbs in it, when you get bonk the carbs gave been reserved for the nervous system which can only burn glycogen, therefore the shock your body feels is that you have switched to fat burning which is slower hence the symptoms.

I do believe that you burn more carbs from HIT but as one poster pointed out these cannot be carried out for much more than 90 minutes, you will of course need to eat Carbs after a session like this to refuel and very quickly as well if you wish to exercise again soon.

However dont over look the fact that a lot of newbies wont be able to carry out these HIT sessions therefore fat burning sessions have a place for them.

If you really want to commit to a weight loss program, get in the gym and lift weights, get those BIG muscle groups aching and you will burn fat all day ...... you will be hungry

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Jimmy Ray Will [878 posts] 3 years ago
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Thanks Dave, the content of this article has been on my mind a lot lately... the myth of the fat burning zone does my nut in.

Also, as highlighted in some comments, I'd like to challenge why some people believe that those inexperienced, or lacking significant base fitness are at risk of injury or damage from high intensity training?

As long as you are relatively warmed up, I can not perceive any greater 'danger' for those lacking fitness as apposed to those who are fit... indeed there is an argument to say that those less fit are less prone to injury from 'smashing it' as their lack of fitness will act as a natural barrier to exercising hard enough to do any damage.

What might risk injury is if a previously fit person was to attempt to train as hard as they did when fit, whilst unfit...

I digress.

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Oolon Colluphid [44 posts] 3 years ago
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I'm interested in the comment above concerning electrolytes. I used to start getting cramp at around 40 miles, even though I still had plenty of energy and a long way to go. I only had water in my bottle, but as soon as I changed it to SIS electrolyte tabs the cramp stopped.

Placebo? Possibly, I am quite well versed in how powerful that can be. But I'd be interested to hear other comments and experiences.

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truffy [650 posts] 3 years ago
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Interesting article. Might have been more informative if there were more DOs to counterbalance the DON'Ts, but I guess that's what we're supposed to pay a consultant for.

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PapaSmurf [31 posts] 3 years ago
0 likes

Not this one,  7

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PapaSmurf [31 posts] 3 years ago
1 like

My wife had not been well and nutrition was difficult to manage, see had cramps in her legs regularly, I suggested she use my High5 Zero tabs x 2 a day, she did and cramps stopped the same day as she started using.  1

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crikey [1251 posts] 3 years ago
0 likes

http://sportsscientists.com/2007/11/muscle-cramps-part-i/
http://sportsscientists.com/2007/11/muscle-cramps-part-ii/
http://sportsscientists.com/2007/11/muscle-cramps-part-iii/
http://sportsscientists.com/2007/11/muscle-cramps-part-iv/

As a start, try the above. Worth bearing in mind when you are faced with attempts to get you buy whichever electrolyte drink or magic tablet which isn't that well grounded in actual science...

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notfastenough [3728 posts] 3 years ago
0 likes

"The simple answer is to choose food and exercise that will control your appetite and hunger effectively, avoid switching on the sugar fuelled ovens in the body when you start the day, and focus on high intensity interval training. Choose foods that don’t encourage the storage of body fat, which in practical terms means that unless you’re exercising hard, set aside the sugar for the builder’s tea."

My wife has been struggling with weight loss for years, so this has got me thinking...

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