Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: neilep on 30/12/2007 16:30:30
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Dear Calorieologists !!
Here's a plate of peppers :
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LOL...apparantely there's 200 calories there !!..yeah right !!...more like 2000 !!
Now here's some fine healthy eating :
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I think we all agree that the Whopper (here in it's healthy eating TRIPLE form) is the king of all burgers and quite simply is ambrosial good eating that is good for you too !!..especially for those of us on a calorie controlled diet !!
What I really want to know is ...what is a calorie ?...how do they determine how many calories a food has ?...and who are ' they ' anyway ?......Is there some kind of World Calorie Body ?
Thanks for your help
Neil
(calorie watcher)
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,,,,,,,,,,and why do those calories taste so good?
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There is a calorie, and a kilocalorie, and they just happen to be the same thing, because nutritionalists don't count the same way as physicists.
Technically, a calorie is the amount of energy required to increase 1 gram of water by 1°C. Then the nutritionalists came along, and decided that a calorie should be the amount of energy that is required to raise 1Kg of water by 1°C.
The problem then is that nutritionalists have a somewhat narrower view of energy than physicists. To a physicist, a lump of coal has a lot of energy, but to a nutritionalist, the energy in a lump of coal is mostly useless to the average human being when eaten, and so the nutritionalist with then claim that coal has no calories at all (because the human metabolism was not designed to burn coal in the same way that it is designed to burn sugar).
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Celery might have negative calories.. Takes more energy to eat than you take in. OTTH it might be a myth.
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Actually, there is a difference between a Calorie and a calorie. Unfortunately, most people don't spot it. It's not fair to blame the nutritionists for a lack of clarity on the physicists' part.
Anyway, to a good aproximation you can measure the calorie content by burning the food and seeing how much energy is released. However for some foods this isn't accurate because there are things like cellulose that burn but are not metabolised (sawdust would give practically no calories (or Calories) if you ate it but plenty if you burned it).
So you have to analyse the food to find what it's made of to get a good measurement of the energy content.
BTW, Happy new year everyone.
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You can get a rough idea of the Calories contained in food with the following calculation:
9.0 x (g of fat) {each gram of fat contains about 9 Calories}
+ 4.0 x (g of carbohydrate) {each gram of carbo contains about 4 Calories}
+ 4.0 x (g of protein) {each gram of protein contains about 4 Calories}
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total Calories
As pointed out earlier, however, cellulose (technically, a carbohydrate) isn't converted to energy in the body, so "fiber" shouldn't be counted (I think it sometimes is, however).
Dick
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As pointed out earlier, however, cellulose (technically, a carbohydrate) isn't converted to energy in the body, so "fiber" shouldn't be counted (I think it sometimes is, however).
Ofcourse, this is an anthropocentric perspective, since clearly cellulose has a high calorie content.
Also, one has to ask what effect cooking has on calorie content (even more so if you burn the food, or at least substantially brown it).
One question I have even about cellulose digestion in humans: while I can imagine that if digestion has to start from the end of the polymer chain, and work its way inwards, that there will simply not be time for our digestive system to go all the way through the hundreds or thousands of glucose monomer components in the polymer; but is it true to say that we obtain no energy from it, or merely that we obtain only a small fraction of the available energy (depending on the chain lengths, and how long it takes to pass through the digestive processes)?
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"while I can imagine that if digestion has to start from the end of the polymer chain, and work its way inwards"
That's not the issue. The cellulose units are bonded together in a different way from, for example, starch; we don't have the enzymes to break those bonds so it has practically no calorific value for us.
Of course there might happen to be some bugs in our stomachs that can digest the cellulose. If we subsequently digest the bugs we would gain some value.
Also, while the reaction is slow, dilute acid will degrade cellulose so some of it must fall apart in the stomach. That reaction doesn't start at the ends of the chain- just where it happens to hit the cellulose right.
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THANKING YOU ALL for your wonderful responses.
It is very much appreciated.
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A calorie...hmmm, you can't see it until it hits your thighs! :) Just Kidding! I meant everywhere! ;)