Drew Eckhardt 

Not as much as you think.

Considering weight alone:

100 pounds is 45 kilograms.

I measured 923kj on my last fast flat 41.8 km ride (26 miles).

Multiplying 41,800 meters by 45 kg, 9.8 meters/second^2 gravity to get force normal in Newtons, and .005 for a high coefficient of rolling resistance yields 92,169 joules. That's about 92 Calories at typical cycling metabolic efficiency, or 10%.

I measured 1932kj on my 104km metric century (65 miles) with 720 meters of climbing (about 2360 feet).

Multiplying 720 meters by 45kg and 9.8 meters/second^2 gravity yields 317,520 joules which is about 318 Calories. Add 229 for rolling resistance and you're up to 547 for a 28% increase.

Aerodynamics are less related to weight but still a factor. Many of us are or were Clydestales due to fat which doesn't appreciably change our surface area and therefore aerodynamic drag in the same position. At my largest I was 215 pounds; in peak cycling form 138. Same drag either way. Height isn't influenced by that. The average American female is about 5'5" versus 5'10" for the average man. Assuming the same proportions that's a 14% difference in surface area and drag.

Willbird

I weighed everything I ate, and did not eat back any exercise except on a few rare occasions. And 5-10 hours of riding a week was good for an extra lb of weight loss, which equals 3500 calories.

Bill

MikeRides

My favorite bike loop, 25 miles with about 1600' of total elevation gain. I always have a headwind for at least 13 miles of this ride (it's a east-west loop). I ride a 30# hybrid, average 14.3 mph, and keep my cadence over 90 RPMs. My Bell cyclo-computer reports a 450-500 cal loss. In retrospect, my StairMaster stationary/winter bike computer claims I lose 1400+ calories for a 25 mile "ride" at a 90+ RPM cadence, with no resistance. 286cal / hour sounds good estimate to me without going into too much scientific research.

JohnJ80

THe problem is that none of this that linear or cause and effect. In other words, if I exercise 3500 calories, at the end of the exercise period, I'll be a pound lighter just doesn't work. For me, I'll even gain weight when I put in a hard period or week of exercising. Then when my body adapts, I'll suddenly in the space of a day two lose a couple of pounds. Sometimes it comes off relatively consistently but it's entirely normal to hit a plateau and for your body to stubbornly refuse to lose weight for a period. This has also been what I have been told by the nutritionist who I consult for my training - her advice pretty much exactly matches my experience over time.

When I go back over the many years of records I have on this, it bears out what the nutritionists and trainers have told me. They've told me to use the numbers from the calculators that I have at hand. When you take out all the ups and downs, it comes out right and the weight loss matches *over time*.

Somehow, I think that the professionals who study this stuff and look at lots of subjects in studies that are peer reviewed are going to come up with the right answer on this. In general, what I've found is that there are tons of hidden calories in a lot of prepared foods. Use simpler foods and weigh them and it's going to come out right. If you want to manage your weight loss, use the calculations from sources you get from professionals in the field that match your weight and exercise intensity.

So my advice is that if you are not losing weight like you would like to be or you aren't sure of your caloric intake vs your exercise burn, then go see a pro and work it out..

j.

Willbird

I'm not sure which calculator you would choose ? You can pick one that gives you pretty much any number you like really. Strava premium using a wahoo TICKR when it uses data loaded in from Cyclemeter halfway makes sense to me. It gave me 946 cals for 2:15 where I did my best to keep HR under 125...34 miles distance 360 feet elevation change.

I have my own numbers for a long time frame, they tell me that those kind of numbers are about right for me.

People using 750-1500 calories per hour do not harm me in any way.....but if they can put out that power level for 3 hours straight they could probably earn a living riding a bike :-).

Bill

ChrisZog

My rule of thumb is take the most reliable calculator that I've found and take 50-75% of the number it gives me. 50% if I felt fresh after the ride. 75% if I practically staggered in the door. After that my next rule is do not unconsciously eat back calories. I allow myself to go over my daily allotment for long rides but am very aware of every extra calorie beyond my normal 2050 (currently). Take today. I did a personal long ride of 33.1 miles. It took about 3 hours. I estimated my burn at about 1700 calories. I've eaten 2200 calories today due to a large dinner and some extra from the ride (coconut water instead of regular water, 2 gels, a Snickers bar... that added up to about 450ish).

I'll probably allow myself a light snack before bed and maybe 1 drink. So I'll end the day at 2500-2800. So even using Wilbird's nice and safe estimate of 400 per hour, easily under my goal. as I go above my normal 2050 and start approaching the 2050+workout I ask myself more and more if I'm sure before every extra thing. Because there really is no sure fire way for me to be positive that 1200, 1700, 2500, etc are accurate. So if I feel extra hungry or want an extra treat after a long ride, sure thing. But I don't think of every weekend as permission to polish off 3500-4000 calories after rides. That and I'd be afraid of getting in the habit of eating 3k+ again and eat that way even on rest days.

Dunbar

Depends on how vigorous. I did a pretty lively 3 hour ride yesterday. I use a power meter and averaged 172w according to Strava (166w according to Garmin) and did 1800kj which is basically equal to calories burned.

Willbird

The guy who is riding 200 miles a day for a year will probably have some solid data on January first :-). There are two guys but I'm talking about the one in the USA . He is using three identical bikes , dunno if he is using power meters

Null66

Work capacity has more to do with it then size... Only accelerating or climbing is there any significant energy difference.

you our gotta be in damn good shape to burn 400 calories an hour...

baron von trail 

600 kcal per hour sounds about right. 750/hr is probably too high. 1000 is definitely not going to happen unless you're averaging 18mph with a dozen stop/starts per mile.

BugDude

I use 65% of the number MapMyRun in bike mode calcs. I arrived at this by using 3 months data of my calories in, basal metabolic rate, and calories burned per MMR. After 3 months I calculated the calorie deficit divided by 3500 to see how many pounds I should have lost compared to the actual pounds I lost. If I took 65% of the MMR number the calculated and actual came out the same. This was using 3 months of data, so a reasonable number of data points. I added a column in my daily tracking spreadsheet to reduce the MMR calories and have continued entering daily values. Over time, it remains consistent with calculated weight loss should be and actual. It works for me.

Dunbar

But that was a HARD ride for me. I was well rested from 3 days of business travel. More typically I'll be in the 450-550/hr range depending on intensity. Obviously the shorter the ride, the more calories per hour you can burn (but less total calories.)

TrojanHorse

The real point is that all of these numbers are estimates. The only number that is NOT an estimate is how far you depress the strain gauge on your scale, and even there you have to consider other variables that can affect the outcome.

Willbird

Well hydration, sodium, and "water involved in digestion" (code for poop) are such huge variables.

But earlier there was a comment about "lots of calories hidden in processed food"...and I got to thinking on that one, if I "ate simpler foods" I could eat more brown rice, baked chicken breast, and cottage cheese. But I lived on that crap for 6 mos one time before and DID cut a lot of weight, but I went a little crazy maybe, and when I found an excuse to go back to eating real food and a lot of it, I did not quit for 8 years :-).

Looking back on it I am thinking when Strava started to get "sane" was when my weight more approached "normal" for a cyclist, and when I started riding a road bike. And some google fu seems to indicate that Strava really is optimized for those things, and the estimates are not nearly as accurate for other kinds of bikes, and for people who are proportioned differently.

Bill

baron von trail 

Definitely want to avoid processed food. Not sure about "hidden" calories, but I am sure that the stuff digests poorly and contains far too much salt, which will retain water and make the scale needle point too far North.

Good rule of thumb: if you didn't make it from scratch, don't eat it.

Avoid carry out like the plague. Never eat frozen microwave crap. Don't touch cold cuts or packaged dried junk. If you must eat bread, stick with whole grains.

andr0id

I use a PowerTap and will agree with the 400-600 kJ/hr range.

I'm 190 lbs and reasonably fit. I get around 600 kJ/hr on a hard 18-20mph effort and around 500 kJ/hr riding a more leisurely 15-17mph.

There's no way anybody is burning 1000 kJ/hr and I'd have to see power meter data to believe 750 also.

Willbird

I am saying this really nicely, not snarky at all, but the power meter has one flaw, it in NO way quantifies..............waving :-).

IBOHUNT

When I had one of them talking scales that started this entire get on a bike when you are 53 years old mess it yelled at me "One at a time!"

I've found that *my* powermeter is pretty close to accurate when I use MFP to track the gazinta vs the kJ vs the scale.

~600/hr = easy ride
~800/hr = tempo
~1,000/hr = 40K TT and that's all I got. Get the rodeo clowns to keep me out the pantry

Willbird

Strava just gave me 680kj for 20.5 miles in 1:08, but I think I earned it :-).

bbbean 

What power meter are you using? How often do you calibrate?

IBOHUNT

20 miles = 2 pizzas. Wait, that's a different thread.

I don't trust STRAVA figures. YMMV

IBOHUNT

Stages and I calibrate before every ride.
Same kind of figures when I had the Powertap hub.

The question becomes how accurate are any of the methods. Within 2%? 5%? 10%

My litmus test is my belt and the scale. One of the reason's I put "*my*". They are *my* numbers... especially the pFTP number

IBOHUNT

Using @Dunbar 3 hour ride with 172W average power I can believe ~1,800

Dave Cutter

The errors in calculated calorie counting... both consumed and burned... are not dangerous. The danger is how our food addicted brains twists a little information to trick us into eating.

I've been there!

I've convinced myself that a 20 mile bike ride could easily make-up for an ice cream cone, or piece of pie (it can't).

I've convinced myself that if I consumed just the calories recommended for the weight I desired while regularly cycling, the pounds would slowly melt off (they didn't).

What I have learned is if I drop my calories intake down to only 1200-1400 a day (base on listed data and an inaccurate app), and if I cycle the same amount of calories off each day (using another inaccurate app) they get me close enough. The weight doesn't fall off... but day by day... ounce by ounce... I lose weight.

IBOHUNT

Data that's been published a lot for calculating food calories vs kJ with the .25 value being metabolic efficiency. That, of course, can vary but generally .22 - .26 is the range that is accepted.

Average power in watts / 1000)x(duration in seconds))/4.184] / 0.25