What is a calorie? – Emma Bryce

What is a calorie? – Emma Bryce


We hear about calories all the time. How many calories are in this cookie? How many are burned by 100 jumping jacks, or long distance running, or fidgeting? But what is a calorie, really,
and how many of them do we actually need? Calories are a way of keeping track
of the body’s energy budget. A healthy balance occurs when we put in
about as much energy as we lose. If we consistently put more energy
into our bodies than we burn, the excess will gradually
be stored as fat in our cells, and we’ll gain weight. If we burn off more energy
than we replenish, we’ll lose weight. So we have to be able
to measure the energy we consume and use, and we do so with a unit
called the calorie. One calorie, the kind we measure in food,
also called a large calorie, is defined as the amount of energy it would take to raise the temperature
of one kilogram of water by one degree Celsius. Everything we consume has a calorie count, a measure of how much energy
the item stores in its chemical bonds. The average pizza slice has 272 calories, there are about 78 in a piece of bread, and an apple has about 52. That energy is released during digestion, and stored in other molecules that can be broken down to provide energy
when the body needs it. It’s used in three ways: about 10% enables digestion, about 20% fuels physical activity, and the biggest chunk, around 70%, supports the basic functions
of our organs and tissues. That third usage corresponds to
your basal metabolic rate, a number of calories
you would need to survive if you weren’t eating or moving around. Add in some physical activity
and digestion, and you arrive at the official guidelines for how many calories
the average person requires each day: 2000 for women and 2500 for men. Those estimates are based on factors like average weight, physical activity
and muscle mass. So does that mean everyone
should shoot for around 2000 calories? Not necessarily. If you’re doing
an energy guzzling activity, like cycling the Tour de France, your body could use
up to 9000 calories per day. Pregnancy requires
slightly more calories than usual, and elderly people typically
have a slower metabolic rate, energy is burned more gradually,
so less is needed. Here’s something else you should know
before you start counting calories. The calorie counts on nutrition labels
measure how much energy the food contains, not how much energy
you can actually get out of it. Fibrous foods like celery and whole wheat
take more energy to digest, so you’d actually wind up with less energy
from a 100 calorie serving of celery than a 100 calorie serving
of potato chips. Not to mention the fact that some foods
offer nutrients like protein and vitamins, while others provide
far less nutritional value. Eating too many of those foods could leave you overweight
and malnourished. And even with the exact same food, different people might not
get the same number of calories. Variations in things like enzyme levels, gut bacteria, and even intestine length, means that every individual’s ability
to extract energy from food is a little different. So a calorie is a useful energy measure, but to work out exactly
how many of them each of us requires we need to factor in things like exercise, food type, and our body’s ability to process energy. Good luck finding all of that
on a nutrition label.

100 Replies to “What is a calorie? – Emma Bryce

  1. A McDonald’s Big Mac combo meal (burger, fries, & drink) is 540 calories. So I have to eat four meals each day to get to 2160 calories. One wonder America has an obesity problem.

  2. you are quite wrong you see when we eat more calories than we need our bodies can automatically burn it just like that when PROPERLY FED it's biology not physics

  3. 0:40 – Not that simple. Watch a video titled 'Why are we still counting calories (History Vs. Science)' by What I've Learned and you will have a much better understanding of what I am talking about.

  4. If 100grams of celery equals 16 calories. Does that hypothetically mean if I could physically eat 87kg of celery (14000 calories) in a week, I would not put on weight if my caloric intake would be 2000 a day. Just curious, not challenging myself to eat 87kg of celery.

  5. Sorry, but isn't it kilocalories (kcal) and not just calories (cal)?
    Or do you mean that by saying "large calories"? Quite confusing.

  6. In primary school we had a teacher that was supposed to teach us about healthy eating.
    THE TEACHER: ok does anyone have any ideas about foods low in calories but that give you a lot of energy.
    ME: but calories are energy.
    THE TEACHER: and that is the end of the lesson bye.

  7. So 1 Calorie is the amount of energy needed to raise 1 kilogram of Water 1 degree Celsius. Presumably you weigh the food. Then burn the food to raise the temperature of the water to determine how many Calories the food has. How accurate could this be when our bodies only rarely are higher than 98.6 degrees. Hardly enough to consumingly burn as fire does. Yes our various digestive chemicals do contribute to our calorie consumption. Yet it must be totally unknown how much of what we eat is totally consumed to get the full Calorie. For instance wood burns very well and therefore has many Calories. Our digestive system very poorly digests wood and most is passed through. So I possibly could eat 2000 Calories of wood and be lucky to absorb maybe 20 Calories. Conclusion is that the use of Calories are insufficient in regards to diet.

  8. “It’s just genetics” yeah eating more than the recommended daily calorie intake every day and complaining that you “exercise” and nothing happens is “just genetics”

  9. 1 calorie heats 1 mL (1 cm^3) of water. Not 1 L (1 dm^3). He's talking about kilocalories, which – by abuse of language – is too often used to describe a calorie

  10. Can we burn calories if staying in cold room? Because our body use the energy to maintain body temperature right? #Curious

  11. This is an Opinion:
    Everyone should know that the word "CALORIES" represents or means how much "ENERGY" a particular food has for intake.
    Everyone should know they need a certain amount of ENERGY through out the day.
    No one should go to bed without eating something. During our sleep our bodies are actually Starving. We need energy to sustain us till morning.
    We need to eat breakfast in the morning to have energy to start the day. We need to eat lunch to have more energy for the day. We need to eat supper for more energy for the evening. We need to eat something before bedtime to sustain us through the night. Remember to also have ENERGY from snacks in between meals. We also need a boost of energy from a drink like Dr. Pepper (if made with sugar cane) at 10:00 a.m., at 2:00 p.m. and 7:00 p.m.

  12. i was literally taught somewhere that excess calories build up like honeycombs in your body which is a good way to look at it. you can burn away the honey in the honeycomb but if you have too much honey your body has to make more honeycombs to store it in thus getting your body to become larger

  13. What this otherwise fine explanation didn't cover is the fact that when the word 'calorie' is usually bandied about, the reference is actually referencing 'kilocalorie', i.e. a thousand (real) calories. The practice is, indeed, so widespread that even so-called 'experts' fail to realize that the common usage of 'calorie' is, well, wrong.

  14. The calorie is the amount of heat energy needed to raise the temperature of ONE GRAM not KILOLGRAM of water by one degree Celsius!

  15. In order to increase the temperature of a 1 Kg of water by 2 degree celsius, do I need 2 calories? If yes, then, can a slice of bread increase the temperature by 75 ºC?

  16. What I got from this video.
    -Calories are units used to measure food energy
    -good luck finding the rest

  17. hi thank you for your sharing but ı have a question. you said "fibrous foods like celery and whole wheat take more energy to digest, so you'd actually wind up with less energy from a 100 calorie serving of celery than a 100 calorie serving of potato chips" ı didnt understand there, ın that case how is it possible to digest fibrous foods with less energy than potatoes?

  18. I don’t get this video, workout trainers always say to eat enough calories but looks like the majority of them are fats and unhealthy yet it’s called energy when you eat that?

  19. Question, if a food has let's say 1000 calories and 100 grams of carbs (4 calories per gram), does the carbs increase the total number of calories in that food?

  20. People often think that the most important thing about losing weight is to excercise but food is the most prominent factor. You can lose a lot of weight just by eating better.

  21. Wow, I had no idea that calories were so complex. Thank you for sharing this information. I never knew just what a calorie was. You're right, we always hear about them but don't really know what they are so sharing this information is pretty valuable and interesting.

  22. "The amount of calories on a nutrition label doesn't mean that is how many calories you're going to get out of it." For someone who counts calories, this is pretty valuable information for me. I never knew that on most things, you don't get all of the calories listed. I always thought that the amount of calories on the nutrition label is exactly how many calories you would get. Thank you so very, very much for making this video. I'm glad I finally know this stuff now because like I said, I had no idea that you don't always get all of the calories that's listed on the label. So now, I definitely have to rethink how I'm going to count my daily caloric intake.

  23. An Idea came to me from this video and if it is true can someone confirm. overweight people might be better at absorbing nutrients from food than skinnier people. Take two people who start at the same weight have the same physical activity levels and eat the same food. Whoever one of then gets to absorb or keep more calories after digestion. This person would gain more weight than its counterparts.

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