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Are intense efforts on the bike better for losing weight? The myth of the fat-burning zone debunked

Find out why when it comes to using cycling to lose body fat, short and sharp is better than slow and steady

If you want to lose weight by cycling, a lot of sources will tell you to do ‘fat-burning’ rides, and even cite research paper that seem to show long sessions of slower cycling lead to weight loss. The reality however is that the interpretation is erroneous, condemning many cyclists to riding along at 14 mph to ‘burn fat’, and to fail to lose weight however much cycling they do.

The misunderstanding of the 'fat burning zone' as a tool for cycling weight loss is understandable given the term's 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. 

2023 Orro Terra E GRX600 E-Bike - riding 3.jpg

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’?

2023 BMC Roadmachine AMP ONE - riding 2.jpg

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.

> Strength training for cyclists

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.

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7 comments

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OnTheRopes | 2 years ago
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The biggest mistake with Long Steady Distance (LSD)  riding is putting too much emphasis on the steady, ride in upper Zone 2 (70-75% FTP) for 3 to 4 hours and you will know about it.

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RoubaixCube | 2 years ago
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Just a friendly reminder that jump rope/skipping burns a hell of a lot of calories and its a good exercise to help with building bone density too as youre on your feet.

The main problem is coming back to it after you done it 30-60 years ago at school. It takes a while to get used to and get in to the rhythm of things

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IanEdward | 2 years ago
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I'm curious about how to eat on long slow rides. My instinct is to eat as little as possible, but I've finished rides a cranky, grumpy mess due (I was advised) to low blood sugars. I wouldn't have minded but family life doesn't really allow for daddy to slope off for five hours on his bike and then return all grumpy for the rest of the day 🙄

How should you fuel 3-4hr low intensity rides?

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Rendel Harris replied to IanEdward | 2 years ago
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It's probably wildly unscientific but when riding for weight loss I check the calories burned as estimated by my Garmin every 30 minutes or so and refuel 60% of them with either cereal bars, gels/sweets or fruit. Through trial and error this seems about right to keep me in calorie defecit without bonking or feeling too drained and ratty at the end.

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OnTheRopes replied to IanEdward | 2 years ago
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IanEdward wrote:

I'm curious about how to eat on long slow rides. My instinct is to eat as little as possible, but I've finished rides a cranky, grumpy mess due (I was advised) to low blood sugars. I wouldn't have minded but family life doesn't really allow for daddy to slope off for five hours on his bike and then return all grumpy for the rest of the day 🙄 How should you fuel 3-4hr low intensity rides?

That depends on how long and how slow your rides are, slow rides should not actually be slow if you want to get any benefit from it, consider it a long interval. Do you know your training zones? Ride in upper half of Zone 2 for a few hours and you will reap lots of benefit.

So far as fueliing is concerned on a 3-4 hour ride (in upper Z2) I would carry a banana or two and usually wont eat it until 2 hours into the ride or 1.5 if I feel hungry. I also only drink water on rides up to 2 hours but longer than that and I will take 2 bottles and have energy drink in the second.

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Simon E replied to IanEdward | 2 years ago
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IanEdward wrote:

I'm curious about how to eat on long slow rides. My instinct is to eat as little as possible, but I've finished rides a cranky, grumpy mess due (I was advised) to low blood sugars.

And I suspect a strong desire to inhale the contents of the fridge.

You won't get the best out of the ride if you don't eat enough. Ideally eat something before going (porridge, overnight oats or something easily digestible) and try to take some carbs on board at regular intervals. I used to go out empty, not eat enough during the ride and it didn't do me any favours.

Just back from 88km and I ate a banana, Torq flapjack and a Snickers* with a second flapjack in reserve. I aim to eat each one before an hour passes since the last item, chewing each one for a while to aid absorption. I'm 165cm (5'4"), bigger riders will usually need more as they burn more calories.

* somewhat smaller than they used to be but still my favourite mid-ride snack in cool weather.

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Awavey replied to IanEdward | 2 years ago
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everyone is different, so what works for me, might not work for you, but I try to eat something every hour on a ride, and drink too, the ballpark figure is 60g of carbs, but its up to you how you do that, you can go for sweets, energy drinks, food, anything.

for me on a 3-4hr ride and I dont care whether people think its low intensity or not in whatever threshold level, Im just riding a bike for 3-4hrs I dont care about that sports science stuff, but Id start with a bowl of cereal, I wouldnt ride fasted, Id take a banana,an energy bar and a couple of gels (just in case) and always consume all the food, the gels depends on how i feel. and mostly that seems to work, and enables me to recover well for the next ride. Because its possible to ride and eat as little as possible, and feel you did ok, or you were extending your fuelling range by doing it, but actually you are impacting your recovery, and your next ride you will feel like your legs arent part of you.

does it mean I lose weight, probably not chunks of it, it keeps my weight reasonably stable and lower than not riding at all, but I find actually just cutting out the rubbish in my diet helps me lose more weight, switching to skinny lattes from full fat, not pigging out on biscuits, or cake too often. Even things like cutting down the amount of pasta, smaller portions, it all helps.

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