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A pound weight is equivalent to around 3500 calories, which is also roughly the amount burned off by walking 35 miles (rule of thumb, 1 mile = 100 calories)
So you can probably cycle a fair old distance on the energy provided by an extra few hundred calories a day, and if you stopped cycling and carried on eating the same, you'd probably put on weight at the rate of roughly a couple of pounds per month - you probably wouldn't really notice for about a year, unless you were very skinny to start with.
The point is, that extra few hundred calories a day might not be noticeable to you, but when multiplied by the population it amounts to a hell of a lot more food.



Engine efficiency doesn't really come into it, and in any case it isn't really affected by vehicle speeds (a small, high-revving engine might have a narrow torque band and so be somewhat dependent on rpm). 55mph is the standard speed adopted (by the EU and others) at which to test fuel efficiency, so that's what manufacturers work to - doesn't matter if the fuel consumption is lousy at all other speeds
When it comes to fuel consumption, a lighter car is better than a heavier one in stop-start conditions, but under steady speed conditions weight doesn't come into it, and aerodynamics start having a lot of say.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

Of course not (to make it clear: we're now not talking about professional touring riders).
Folks who are trying to lose weight or keep fit generally don't try to eat more; it is usually the other way around. As it is, a great many folks take in more calories than they burn, hence they're a little bit bigger than they otherwise would have been. So increasing the calorie intake in proportion to new exercises, for someone who already eats more than they burn, does what?

PS: I've not passed any comment on any 'green' aspect of this.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

No Pete. The point is this. When a sedentary person decides to leave his car at home and go to work on the bike he probably doesn't increase his calorie intake at all. Especially if the reason, a very common reason, for taking to the bike is to loose weight.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

Apparently cycling to work is one of the biggest causes of heart attacks

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

if that's all you are getting at the gym then I suggest you save the membership fee and get out on the road. As long as you are putting the effort in you should be burning a good bit more than 800 per hour. If you are only going to plod along at 15mph though it will be quite a bit less.

Anyone thinking of taking it up should realise you can get a bloody long way from home in an hour on a bike, don't forget you need to get back again.

Dusty: I assume you don't cycle since you seem to think people slow down for cyclists.

I think that an interesting article so placed it here for any further discussion.

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I couldn't give a damn how green or not cycling is. It's considerably better for my wallet and that's a win !! (About a grand a year)

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My friend who calibrates gasoline engines for a leading car manufacturer likes riding his bikes. he's got some sort of dyno in the hub of his race bike that tells his Garmin thingy what's what. He said last night that he can generate about 100 watts so travels about without using much energy ( he is surprisingly concious or energy considering he does what he does).

The general perception is that this is free energy, but people run on food and food needs to be produced/grown. It would be interesting to compare how much energy is used biking when the extra food eaten is taken into account.

100W sounds a bit low, even by my standards! That said, it is testament to the staggering efficiency of a human on a bike. As for the "extra" food consumed, well, isn't that the point? You do this sort of thing to burn off calories, not replace them, don't you? I think people use a couple of thousand calories a day just existing. The stuff they "burn" in exercise is remarkably little extra on top of that.

100 watts is fairly gentle cycling and at that level most people wouldn't need to eat any extra food. Nearly every one in western society consumes about twice the number of calories than they need just to exist. Mild to moderate exercise merely uses some of that excess, possibly reducing weight gain. Indeed, I am told that some people exercise for the reason of loosing weight without dieting.

Driving to the take-away for a pizza is ungreen not just because you drive, but more because you don't need the calories from the pizza.

Of course an athletic cyclist, like ed, could be averaging up to 400 watts and I imagine that he does eat hearty.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

Not sure what time period you're averaging over my hard intervals at the moment (30sec to 2mins) are 300W+, and yes 'hearty' would be one way of describing it.
My comment on power output was here viewtopic.php?p=236284#p236284 with ~150W on easy mode, I can PM a link to more detailed data if people are that bored.

Bit dissappointed no one has critiqued my MPG conversion (viewtopic.php?p=236266#p236266), since all our measures of efficiency for cars discussed so far seem to have been based on a starter motor! I threw it together so suspect it's wrong but will assume for now everyoen agrees with it

According to this http://blog.mapawatt.com/2009/07/19/bicycle-power-watts/ Ondrej Sosenka was averaging 430watts when he broke the world hour record. Since the hour is the ultimate test of cycling abiliy that probably represents a maximum for the period, but I imagine that in road or track sprints a peak power of over a kilowatt might be achieved.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

Just to add, I seem to remember him saying he could generate about a third of a hp for about 20 minutes. He's a pretty fit 50 something.

OK, I can find a Carbon Trust figure that roughly agrees with your 9.5kWh / litre figure. I can then follow it all the way through to the last step. I get 4.2E-4 m/J rather than 4.5, but same ball park.

How do you then get the last bit though? Where did the 200J for 2m on a bike come from?

200J seemed to be dusty's benchmark at the start of the thread for his starter motor (viewtopic.php?p=236258#p236258) so i was just normalising my calculation against this for comparison.
(although my power data suggests >6m for 200J on the bike)

I don't eat any more on days I cycle. I eat more on days I'm sat around the house doing nothing.