Calorie curiosity

NorthCascades
NorthCascades Posts: 10,968 Member
edited November 2024 in Health and Weight Loss
When we say that a food has x calories in it, are we talking about the energy we humans can extract from that food, or an intrinsic property of the food? If a dog steals your burger, it would be a different number of calories for the dog? Maybe a better way to phrase the question is: if gasoline was in the food database, would it be zero calories even though it's extremely dense with energy, because our digestive system can't get any energy from gasoline?

Replies

  • NorthCascades
    NorthCascades Posts: 10,968 Member
    ahodgeface wrote: »
    Scientifically, a calorie is the amount of energy(J) needed to raise either a gram of water by a degree Celsius or the energy (kJ) needed to do the same for a kilogram of water (kcal). Equivalent to just over 4 joules. It can be worked out just by burning food. More calories, more energy it contains regardless of who's eating it or burning it. I'm sure fibre, which is mainly cellulose, contains calories as it is made of glucose, but we don't actually digest that so it doesn't provide us with energy. So I guess it's more that substances will have calorie contents, but some are not accessible to us and therefore irrelevant.

    So if fiber is a carbohydrate it should have 4 calories per gram, but we count it as zero because we can't digest it, it gives us no energy. Thanks, that's a great example. I'm guessing gasoline would be "zero calorie" even though our cars can get about 36,000 calories per gallon worth of energy from it. It sounds like when we talk about the calorie content in food we mean what a human can make use of. Thanks.
  • garystrickland357
    garystrickland357 Posts: 598 Member
    I believe the calorie counts for all substances be it gasoline or a Snicker's bar are determined by burning them in a calorimeter. That means the lab actually burns the material and measures the heat released. So from that standpoint calories are all equal.

    As in so many of our discussions we wouldn't drink gasoline (I know you didn't imply that). My point is that those items we do consume are largely digestible and usable as an energy source. I don't believe energy labels reflect the "usable" energy in the food - rather their actual heat/work equivalent.

    I may be wrong.
  • robthephotog
    robthephotog Posts: 81 Member
    Pretty sure its just the measurement of energy given off as thermal energy when a substance is burned. So its not the consumer per se affecting the number of kcals. Its up to the consumer whether it/we can ingest and utilize whatever substance is entering the body.

    So much like a dog shouldnt consume certain forms of chocolate, we cant consume gasoline, bleach, etc. Even though such substances have high kcals per weight.

    Its fairly black and white if you think about it that way.
  • CarvedTones
    CarvedTones Posts: 2,340 Member
    About 25% of the calories in whole almonds comes out in your poop (don't think I would have liked being a research assistant on one of those studies). I assume the subjects still chewed them instead of having to eat them whole. I saw another article that I want to say found 15% difference in crunchy versus smooth peanut butter; but I don't have that link so I am not as certain. Almond one below:

    http://www.berkeleywellness.com/healthy-eating/food/article/are-nut-calorie-counts-wrong
  • lynn_glenmont
    lynn_glenmont Posts: 10,220 Member
    NorthCascades wrote: »
    When we say that a food has x calories in it, are we talking about the energy we humans can extract from that food, or an intrinsic property of the food? If a dog steals your burger, it would be a different number of calories for the dog? Maybe a better way to phrase the question is: if gasoline was in the food database, would it be zero calories even though it's extremely dense with energy, because our digestive system can't get any energy from gasoline?

    Who are "we" and where are "we" getting our information from? If it's from a nutritional label, the methodology behind it is going to be determined by a regulatory body in most cases, which may differ from country to country, and some countries allow more than one methodology as acceptable (e.g., straight calorimeter measurement, measurements that take into account partial indigestibility of fiber, etc.).
  • FL_Hiker
    FL_Hiker Posts: 919 Member
    edited November 2018
    A calorie is a unit of energy. It’s determined by burning the unit, an exothermic reaction (-delta G) which releases heat which we then measure. Our bodies break down energy slowly in a process called glycolysis so that it can be used efficiently and not all wasted as heat in a single step, therefore each step has corresponding enzymes. Another way to look at it is that sugar has energy, it sits on your shelf and is a favorable reaction... however it doesn’t just spontaneously combust right? Over time many many years it would break down... but a certain enzyme can be used to speed up the process. A car does not have the enzymes or machinery to break down a cheeseburger. Have you ever wondered how artificial sweeteners work? They taste sweet but don't have any calories? They mimic a molecule our taste buds can recognize (i.e. bind to a receptor) but we cannot metabolize them.
    The calories are the same for a dog... I actually calculated once how many calories my dog eats and it was astonishing. His food has all the nutritional info on the back it’s pretty cool. He gets 4 patties a day X 398 cal ~ 1590 calories a day plus his snacks. He’s about the same size as me and he eats about the same amount of calories lol. However those calories are specific for his species, he eats mostly protein which is easy for him to digest.
    8ug1500og56m.jpeg
  • AnnPT77
    AnnPT77 Posts: 38,129 Community Helper
    NorthCascades wrote: »
    When we say that a food has x calories in it, are we talking about the energy we humans can extract from that food, or an intrinsic property of the food? If a dog steals your burger, it would be a different number of calories for the dog? Maybe a better way to phrase the question is: if gasoline was in the food database, would it be zero calories even though it's extremely dense with energy, because our digestive system can't get any energy from gasoline?

    Man, I thought I over-thought stuff. I'm an amateur.

    ;)

    Are you certain we can't get any energy from gasoline? Have you tried? (There are lots of strange additives in there; maybe some are digestible.) If we drink gasoline and die, do those calories count against one's daily goal?

    ;)
  • hamelle2
    hamelle2 Posts: 297 Member
    Curious...who calculates the calories for every item on every restaurant menu? Are there labs all over the country?
  • mbaker566
    mbaker566 Posts: 11,232 Member
    edited November 2018
    some foods are a known quantity which is why we have tools like the recipe builder and we don't need to do an experiment every time we make a meal to know what the estimated calories are. same for restaurants

    i would think gasoline would be zero calorie because we cannot use it. we cannot access the available energy. we might be able to access a few calories but we would probably die before the calories were countable
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