The concept of CICO and calorie counting via analogy

Aaron_K123 Posts: 7,122 Member
edited May 2018 in Health and Weight Loss
Pretend you have a car. Okay probably you do have a car but pretend you have a rather unique car. This car has two tanks, a normal tank that you can pump fuel into and another reserve tank that the car can draw from if the main tank is empty. The main tank is rather unique in that it can take a huge variety of different fuels…gasoline, bioethanol, butane, propane…you name it. The reserve tank though is only gasoline and your car can convert whatever you put into the main tank into gasoline to top off the reserves, provided there is fuel to spare. If you use up all of your fuel in the main tank it will start to pull from the reserve tank.

Now pretend you want to find out exactly how much fuel you’d need to have in your main tank to drive 300 miles without having to pull from your reserve tank which you want to maintain. If this was a normal car that took only gasoline you could just divide the 300 miles by the miles per gallon your car is listed as getting in your user manual and get the number of gallons you need. Unfortunately, this is not a normal car. You can put multiple fuel types in your car and in fact your car really doesn’t work that well if you only use one fuel type. Unfortunately, the different fuel types have different amounts of energy per volume and therefore 10 gallons of one type might not be the same as 10 gallons of another type…so it doesn’t make sense to track volume, you want to track energy instead. There are lots of units for energy just like there are lots of units for distance: there are joules, BTUs, kilowatt-hours and calories. It doesn’t really matter what unit you choose to use, just like you could give the same distance in miles or kilometers or inches. Lets choose calories then. So you need to figure out how many calories you need to go 300 miles and then put that many calories into your tank. But how do you figure that out?

Well your car weighs a certain amount and you can find that in your owners manual…here it is, 1000 kilograms, and you want it to go over a certain distance, 300 miles. So you could try to calculate the amount of work (energy) it would take to move 1000 kilograms by 300 miles. Lets call that the calorie output or CO. Now, of course, whatever you end up calculating is going to be a wildly off because it doesn’t account for everything like friction between the wheels and the ground, the friction of the moving parts in the car, the generated heat, the noise generated, the amount of time you are idling versus moving etc etc. So what do you do? Well luckily there are lots of studies out there of cars very much like yours and how much energy they require in calories to go a certain distance in miles. Sure, they aren't exactly all the same car but if you put in your make and model and year you can get a decent estimate of how many calories you need to go a certain distance. So now you have a ballpark number now for CO…what is next.

Well you know roughly what CO you need so if you want to use exactly that much fuel without going into your reserve tank you know you need to input the same amount of calories that you output…so you you need to match your calorie output (CO) with your calorie input (CI). You can look up the calories per gallon of the various fuel types you have on hand and you can count them up and put together a fuel plan to hit your target. So that is it right? Not quite. You see the calories per gallon of the fuel is the amount of calories you would get from that amount of fuel if your engine was 100% efficient. Your engine, however, is not 100% efficient. In fact, it isn’t even the same efficient for the different fuel types. Not only that but you look in your manual and there isn’t any info at all about how efficient your engine is. So you know two things…the maximum number of calories possible to obtain from your fuel and the fact that your engine isn’t actually going to get that much out of it. You don’t know by how much it will fall short though or if your engine might be more efficient with certain fuels than with other fuels.

So are we stuck then? I mean if you had the ability to exactly calculate the CO and exactly calculate the CI that your particular car would get out of the fuel then it would be easy to balance the two…CI=CO. But it seems like that is impossible. So what do you do? Well perhaps the situation isn't as dire as it looks. Since the value you got for CO was based on averages from similar cars and how many calories they required to go a certain distance that value already actually took into account the average efficiencies of those cars engines. Since there are millions of cars out there that have roughly the same make, model and year as yours those estimates aren't too far off the mark. As it turns out those studies have shown that there isn’t all that much variation between engine efficiencies no matter what kind of car you have and it has allowed for the creation of calculators that adjust CO based on how much your average car gets out of your average fuel mix and gives you a rough approximation of what CI you need regardless of the actual efficiency of your engine. So now you can look it up with a calculator that if you are driving a 1000 kilogram 1979 car 300 miles you are going to need 30,000 calories and you can load up on a mix of 30,000 calories worth of fuel and hit the road.

You super accurately measure your 30,000 calories worth of fuel down to the milliliter and you hit the road. About 285 miles into your journey a warning light flashes on in your dash…you are starting to pull from your reserve tank! Oh no…what happened? What went wrong? Is the CICO principle just wrong? Are all the calculators junk? You measured as carefully as you could and used the calculators that were available! Well, no…nothing is wrong with the idea of CICO…what is “wrong” is that the calculators are based on assumptions of engine efficiency and energy expenditure that are based on population averages not on you personally. So what do you do? Well. You note that the amount of calories you put in your tank doing this particular drive got you a distance of 280 miles before you started dipping into your reserve tank. What happens if your car doesn’t have a nifty warning light that you are going into your reserve tank? Well…you could always weigh your car before and after your drive and get an idea of how many calories you expended and how much you dipped into your reserve because as you burn those calories in your engine and expel them as CO2 and H20 your car gets lighter. If your car weighed 1000kg and you put 5kg worth of fuel into it and the car ended up weight 999kg at the end of your drive you'd know you used up the 1kg of gasoline from your fuel reserve.

So you started with what the calculators told you which was a rough approximation and found it wasn’t quite right for you. So you diligently track the amount of calories you put in your fuel tank (CI) and the amount of miles that you travel (CO) and how much fuel is left in your reserve tank and after a few months of tracking you learn how to adjust those initial estimates so that you know pretty much exactly how much fuel you need to go a particular distance for your particular car no matter what types of fuel are available to you.

Later you run into someone who asks you how you keep only spending exactly what you need to get somewhere and not over or underspend and you tell them you track your calories. They scoff and say that they tried to track calories and it didn’t work for them at all. They were super diligent about tracking but if they put 30,000 calories of 80% butane and 20% propane in their car they were able to go 290 miles but if they put the exact same number of calories of 20% propane and 80% butane into their car they only went 250 miles so clearly CICO is wrong. Another person overhears and pipes in their own opinion arguing that no matter what car you drive 30,000 calories of any type of fuel will allow you to travel exactly 280 miles no matter what and anyone who is off by even a mile is clearly just measuring wrong. You just smile and check your log to see how much you need to get to the next town.

Truth is CICO is just is concept referring to the fact that if you know how much energy you are expending you know how much energy you need to balance that. It is just a fact of math and nature. Trying to get accurate estimates of CI and CO though isn't exact and is based on population averages that don't always apply. That said if you count your calories consistantly and track your reserve tank you can correct for any quirks that your car might have relative to the average. With some diligence and accurate honest tracking you will end up with a tailored model for you that will get you exactly where you need to go.


  • mph323
    mph323 Posts: 3,566 Member
    Perfect! Thanks for taking the time :)
  • AlphaHowls
    AlphaHowls Posts: 1,779 Member
    *dew claws up*
  • NextRightThing714
    NextRightThing714 Posts: 355 Member
    I enjoyed it. Thanks for sharing!