New Cyclist- am I really burning this many calories?!

EverestDreamer

Hi all,

Not taking cycling too seriously as I use it purely to train for my mountaineering and find it builds a lot of power. I'm formally a half marathon runner but have had to stop due to injuries, cycling has been fine.

I'm an 18 year old highly-metabolised teenager at 6ft 4 with a very lean build. Since starting cycling and upping my distances I've been amazed at the amount of calories my Garmin says I'm burning. I've checked these online and it seems it's not lying.

When I read online about distance cycling I get the impression that I'm overeating despite the amount of kcals burnt and that most cyclists only seem to live on gels- they say they eat a lot of carbohydrate and protein but don't ever specify exactly how much or what they're eating to get it. I really don't know if I'm eating enough but I do find it hard when I'm cycling 80-100 miles and burning over 4000calories. On a 40 mile ride at about 160bpm I can burn 1700-1800 calories. Is this normal?

I literally don't stop eating- high protein, lots of healthy fats, very little dairy, very little refined carbs or sugar apart from when training. On the shorter rides I may bring one gel, with a breakfast of a large bowl of porridge (100g) with berries, banana and peanut butter- or a peanut butter banana toastie. On longer rides (80 miles+) I'll have toast and egg as well, bring 3-4 gels then stop for a cake or something half way on the ride. I don't seem to get gastric distress when I eat fatty foods during the ride.

I'm cycling anywhere between 3-5 times a week, up to 200 miles a week. Have I got permission to eat as much as I want?! I'm not trying to be super fast or lose weight- just maintain it! It seems I have to eat a huge amount on training days to meet my calorie demands.

drlodge

I reckon I burn about 600kcals an hour. For a 100 miler, that's about 6 hours cycling so 3,600 kcals. Or nearer to 4,000 if you're working harder/going faster.

Some people cycle simply so they can eat what they want. 200 miles per week = say 7000 kcal, so you should be eating at least 3,500 kcal a day compared to the "normal" recommended 2,500.

meanredspider

Yes - I reckon 600kcals/hr is what I burn on average at a tempo pace - that's what my power meter is telling me too. I think you aim somewhere in that region you won't be too far wrong.

I once had a diet put together by a sport nutritionalist based on 160-200 miles a week. It was high protein and, frankly, I really had to work at it to eat what was required. I never want to see another slice of turkey ever again!

Miss Pootle

I think for it to be more accurate you need to input your age, weight and sex, and wear a heart rate monitor. I thought I was burning hundreds of calories until I started using the heart rate monitor and found I was only burning 2/3 of what my Garmin said before. I must be the only person who has finished a 100-miler fatter than I started it!

meanredspider

Miss Pootle wrote:

I think for it to be more accurate you need to input your age, weight and sex, and wear a heart rate monitor. I thought I was burning hundreds of calories until I started using the heart rate monitor and found I was only burning 2/3 of what my Garmin said before. I must be the only person who has finished a 100-miler fatter than I started it!

Garmin is hopeless - it way overcompensates. For a ride I did recently I had two Garmins running. One was recording everything (including, most importantly, power) the other only tracking me. The one tracking me recorded 8000kcals for 9 hours of the ride where the other recorded 7500 for the full 12.5 hours taking into account power. But, honestly, if I used 600 per hour, I'd be very close.

cougie

Theres a calculation for running thats meant to be fairly accurate - cycling is much harder to work out with the extra speed and drag and winds etc.

For me - when I run - its about 100 cals a mile. So if a 40 miler felt like an 18 mile run - then yeah it could be 1800 calories burnt - but its not.

JayKosta

Yes, you could easily be using 500-600 calories per hour - if you're riding fairly hard and not at a 'leisurely pace'.

Jay Kosta
Endwell NY USA

kajjal

Also how hilly and windy have a big impact.

TakeTurns

I started riding at 17 and was your height. I'm 20 now and 2 inches taller. Joined a club 3 months after I started riding so was already doing big miles from the go. I was eating so much more food it was crazy. I never used to have packed lunch but started to bring food from home to school and would snack between lessons. I also had this awesome 2 litre bottle which I would fill with lots of blended fruit mixed with water. I'd just down that throughout the day and it'd be a great carb boost for a post school ride.

My mum even had to increase her shopping load and cook larger meals. In the end she gave me £50 a week to buy extra food because I was getting through so much that she couldn't keep up. I think at the start you'll eat a lot but then you'll become a bit more efficient and burn some fats too. Also being young and tall means your body goes through food very rapidly and needs much more than your average joe.

Alex_Simmons/RST

Unless you are measuring power output with a good and calibrated power meter, calorie numbers provided by cycle computers are nothing more than light comic relief.

Even with a power meter you'll only be within ~10%, perhaps a bit tighter if you have good information on your typical gross efficiency level.

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

TakeTurns

Alex_Simmons/RST wrote:

Unless you are measuring power output with a good and calibrated power meter, calorie numbers provided by cycle computers are nothing more than light comic relief.

Even with a power meter you'll only be within ~10%, perhaps a bit tighter if you have good information on your typical gross efficiency level.

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

Interesting, so the fitter you get, the more calories you're burning. Even if you're out for a Z2 ride, simply because you're able to put out more watts at Z2 than before? Even though the perceived effort seems the same...

Alex_Simmons/RST

TakeTurns wrote:

Alex_Simmons/RST wrote:

Unless you are measuring power output with a good and calibrated power meter, calorie numbers provided by cycle computers are nothing more than light comic relief.

Even with a power meter you'll only be within ~10%, perhaps a bit tighter if you have good information on your typical gross efficiency level.

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

Interesting, so the fitter you get, the more calories you're burning. Even if you're out for a Z2 ride, simply because you're able to put out more watts at Z2 than before? Even though the perceived effort seems the same...

Assuming you ride same duration, then yes.

Over same distance, not as much since you ride faster and Work = Power x Time (more power, less time). It will still be more as air resistance means power is not linear with speed but a cubic relationship. In real life though other factors introduce a lot of variables that can mask such things (stops and starts, wind, gradients and road surfaces etc).

drlodge

Alex_Simmons/RST wrote:

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

Sounds right...I reckon my average power output is around 150W which comes back to 600 kcal/hour. Or thereabouts. YMMV (or should that be YPMV) of course.

Escher303

Alex_Simmons/RST wrote:

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

That's a lot more than I expected. For example the ride I did on Saturday was 6.5 hours averaging just over 200 watts for the duration, that'll be over 5000 calories? Hadn't realised it was as much as that. Thanks for the info.

cougie

drlodge wrote:

Alex_Simmons/RST wrote:

As a guide, for every 100W of power at cranks (on average), you'll metabolise ~1700 +/- 200 kJ per hour (~400 +/- 45 Cal per hour).

Sounds right...I reckon my average power output is around 150W which comes back to 600 kcal/hour. Or thereabouts. YMMV (or should that be YPMV) of course.

that sounds a bit high to me. If I go for a steady run - I'd cover about 6-7 miles an hour. So 600-700 cals roughly.

An hours running is far harder than an hours cycling. Unless you're climbing a mountain or something ?

Alex_Simmons/RST

Energy through cranks (kJ) = average power (W) x duration (seconds) / 1000
Energy metabolised = Energy through cranks / gross efficiency (typically 0.19-0.24 for cyclists)

So 100W for 3600 seconds = 360kJ
Metabolised = 360kJ / 0.215 (say) = 1675kJ

1 Cal (or kcal) = 4.18kJ

= 1675kJ / 4.18 kJ/Cal = 400 Cal per hour

Running is harder on the body due to impacts and eccentric muscle contractions that don't occur when cycling.

cougie

That makes a lot of sense.

foggybike

I always work on 400-500 per hour.

wongataa

Looking at my Garmin 800 data it claims I do about 600-700 calories an hour on my rides. I do use a heart rate monitor with it. I take the numbers with a good pinch of salt but they could be in the rough ballpark of the real value.

meanredspider

I work on the basis that 1 kJ through the cranks is worth 1 kcal burned as a rough rule of thumb. Garmin uses something close to that (for me) when I've ridden with power. Strava uses a slightly higher number.