How do they figure out how many calories are in a food? Especially corn.
Hedgehog
Hi, Ranger
<font color=“red”>heh heh heh heh heh, they burn it! Burn, burn, fire fire fire!</font>
No seriously, they take the food (or a small amount of it) and they burn it to see how long it fuels the fire. The longer the fire, the more calories it has.
OR, they just take a WAG of how much fat, protein, and carbohydrates (suger, and starch) is in the food and add up the calories from there, knowing that:
1 gram of fat has 9 calories,
1 gram of protein has 4 calories, and
1 gram of carbohydrates has 4 calories.
And that’s how you find out how much calories food has.
“The more beautiful the rose, the more thorns it hides underneath.” - Louie
but how do they accurately tell how many calories a person will consume if they eat something like corn which is never completely consumed.
for references check your potty
anonymouse
Cecil on calorie content determination:
http://www.straightdope.com/classics/a3_097a.html
A true Straight Dope scientist would take an equal amount of “corn” from his stool, burn it and subtract the difference from the undigested calorie content. Any volunteers?
I don’t believe any adjustment is made for the calorie content of… err… output, but I could be wrong.
By the bomb calorimeter method, a nice juicy chunk of southern pine would have roughly the same caloric content as an equivalent weight of cornstarch. However, while your body can absorb the calories in cornstarch, you can’t digest cellulose.
Why was it determined that the engergy freed from burning something was the same as the energy available to our bodies. Last I looked I don’t pee ash. Does my body “burn” these molecules with similar end products? Is it at all possible to measure this sort of thing? Does 1 Calorie of peanut butter equal 1 Calorie of enery at my disposal (taking into account energy release as heat in my body)?
Thin – it’s the same chemical process, only slower. You start with sugar and end up with carbon dioxide and water. It doesn’t matter (energywise) how you got there, just that you start and end at the same place.
And yes, one calorie of digested food equals one calorie of energy available to your body. Their is obviously some loss – digestion isn’t a perfect process – but the human body is a remarkably efficient machine.
Two caveats – the food energy isn’t converted immediately to heat, that would be wasted. Mostly it’s converted to intermediate chemicals, primarily ATP, that are used to drive the cellular machinery. Second, the dietary “calorie” is actually a kilocalorie in chemists’ units. Don’t ask me why. It just is.
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
Thanks!
I always thought spelling it Calorie instead of calorie implied kilocalories. Same for the abreviations C. and c.
Mr. T – You’re right. Calorie does imply kilocorie. But only if the know-it-all critic notices. 
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
Well, that came out well. I’ll try again. Calorie == kilocalorie.
(Does using == give you any hints about which computer language I use?)
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
C or C++ of course. I use a lot of = (equivalence) and := (assignment) in the language I’ve been using. All lines end with semicolons though;
Anywho, frequently, in books pushing one diet or another, there’s always a reference to how many miles (kilometer) you can run on a tablespoon (15 ml) of peanut butter. How far do the books typically give as the distance? Anyone? How does one measure energy consumed by a running human. Respitory chemistry? It’s not just mechanics is it?
Oh, dear me. Pluto I see you called me Mr. T and I didn’t call you a sucker or a fool. Sorry. Wasn’t paying attention.
Mr. T: Character, actor, whatever on the T.V. show “The A-Team”
Looks like it’s just you and me, Mr. Thin, on this topic for a while anyway.
You can measure energy consumption in a running human by having him (or her) run on a treadmill and keep track of his oxygen usage. It’s fairly cumbersome but it’s done all the time. The runner breathes through a mask over his nose and mouth and the chemical composition of the before and after air is analyzed. Oxygen is consumed and carbon dioxide and water are returned in proportion to the food energy being converted by the body.
As a refinement, not all of the energy is used for running. A certain percentage is used for pumping blood, brain activity, etc. This can be measured in the same way as the running test, only keeping the subject as still as possible. The rate of energy consumed while resting is the basal metabolic rate, or BMR.
Once you’ve established a baseline for energy usage while running, walking, skipping, resting, etc. then it’s straightforward to calculate things like how many miles you can run per Calorie.
Incidentally, at the same time you can measure how much energy goes into the treadmill by mechanical means. Once you know the energy consumed and the energy delivered, you can measure the efficiency of the human body. I’ve forgotten the exact figures but … well, I’ve forgotten even the inexact figures. I’ll get back to you on that. Anyone out there that can help?
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham