# – What exactly are calories?

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What are calories? Is it the amount if energy in a food? How does the body uses calories, burns calories, and how does excess calories becomes fat?

Why are food “low in calories” good for you? Why are food of the same size, have different amount if calories?

In: 0

Fire, bad! But in the body calories or Calories (logarithmic thing) get lit on fire to produce the energy we need. Excess sugar gets turned into fat like a 4:9 ratio or similar in terms of calories. The body is very good at making sure you ~~don’t starve~~ die from starvation

One calorie is the amount of energy required to raise one ml of water by 1 degree Celsius.

The rest of your questions are subjective as hell, and/or a can of worms to explain

>What are calories? Is it the amount if energy in a food? How does the body uses calories, burns calories, and how does excess calories becomes fat?
>Why are food “low in calories” good for you?

Yes, a “calorie” is just a unit for energy. Things like the Joule, the Wattsecond and the calorie are units for energy in different contexts, just like the meter, the inch and the lightsecond are units for distance in different contexts. But they all express the same property and they can all be used interchangeably.
Energy is an abstraction of the capability to perform [work](https://en.wikipedia.org/wiki/Work_(physics)), which is a bit of a roundabout definition, but it doesn’t get much better than that, I’m afraid. Boiling a liter of room-temperature water, for example, requires a work of about 1 kWh or 3600000 Ws or something like 800000 calories (or 800kcal if you will).

Food that is low in calories is just that: low in energy that is usable by the human body.
Or rather “lower than comparable foodstuffs”. A TicTac isn’t a low calorie food, even though it contains far less energy than a head of lettuce.

As others have answered the first part im going to ignor that.

Low calories is not inherently good or healthy, your body needs some energy to keep running, normaly about 2000cal a day. Not havig that means your body burns fat and you loose weight. Being low calorie is just a good thing if your goal is to loose weight. And different foods have different calories for te same volume because they are made out of different stuff, a tomato is mostly water, that has zero calories, a steak is fat and protein, both have calories.

Food has two purposes: First, it supplies your body with fuel, to give energy to, e.g., your muscles, your brain, and everything else that does work. And second, it provides building material, so that your body can assemble new cells or repair things in or between cells.

The fuel part, you can imagine very much like gas for a car. It’s something that can be burned to give power. And “calorie” is just a unit of energy. For example, 1 kWh (the unit you know from your electricity bill) is 860 kcal (calories), and 1 litre of gasoline gives your car 8.7 kWh or 7500 kcal. And it’s no coincidence that one litre of cooking oil gives your body about the same (8000 kcal, if you’d actually drink it in one go.)

So, nothing wrong with calories. However:

*Most* of the calories from food that your body cannot use, it will store as fat. If you are an average male with an office job, your body needs about 2000 kcal per day. If you eat more, say, 3000 kcal, the food with the left-over 1000 kcal will be transformed into fat — and you gain about 110 grams of body fat every day.

Certain types of food contain different amounts of calories because of the chemical composition of the food. For example, fat or oil is very high in calories per gram. Fiber and protein contain low amounts of calories so they don’t provide your body with much energy but they are important for other purposes. When the food is broken down in the cells the energy stored in the food is converted into usable energy for your body. Your body is constantly using energy for various functions, and your energy demands increase if you are active or growing. Moving your muscles, healing injuries, and forming new cells all use energy.

The calories that a food “has” is actually the amount of calories your body has to use to burn that food off. Your body only uses a set amount of calories each day and you can add more with exercise. If you take in more calories than your body burns, you gain weight. If you burn more than you eat, you lose weight. It takes 3500 excess calories to gain a pound and 3500 in deficit to lose a pound. For example, if your body burns 2000 calories per day and you eat 1500 calories per day, you’ll lose a pound per week. This is why it’s so hard to lose weight and extremely easy to gain it.

Your body turns most of the food you eat into glucose (a type of sugar), then feeds that glucose to your cells as fuel. Some bits get used as building blocks, but most of it just gets burned for energy.

Your cells absorb the glucose, combine it with oxygen from the bloodstream (basically burning it, but more controlled), and use the energy this gives off to power all the being-alive stuff they do – muscles, metabolism, immune system, growth and repair, basically everything. Burning the glucose gives off CO2, and your blood returns that to the lungs so you can breathe it out, and grab fresh oxygen from the air.

If you have more glucose in your bloodstream than you need to power your cells right now, your fat cells wake up and start combining glucose molecules (along with some water / etc) together to build fat molecules, and secreting the fat into the surrounding tissues.

At a later time, if you don’t have enough glucose in your bloodstream to power everything, your body will start scavenging fat from your tissues, and your liver will break it down into glucose again, and use that for fuel.

(there’s actually a whole buffer system of stuff called glycogen that it keeps on hand before it goes for the fat, but let’s not complicate things)

The amount of usable energy that can be extracted from food (via the amount of glucose you can turn it into) is described in terms of calories – a measure of heat. One calorie is enough energy to warm 1ml of water one degree.

A small gotcha is that when talking about dietary stuff, it’s actually measured in *kilo*calories – enough heat to raise a whole litre of water one degree, but they call those ‘calories’ anyway just to be difficult and annoying.

Very roughly speaking, if you burned a tictac in a spoon and then stuck that spoon in a carton of milk, your milk would get about a degree warmer.

Obviously if you keep eating a bunch of foods with a whole lot of calories, more than you need, then your fat cells are going to keep busy turning all the leftover glucose into fat, and you will get podgy.

If you keep eating less food than you need to cover your energy requirements, then you’re going to keep scavenging fat from your tissues, and you’ll get thinner.

Different foods have different amounts of calories per gram, because a) not everything can be turned into glucose, and b) of the things that can, some can be converted into a whole lot more of it than others.

Fats are extremely calorie-dense, which is why our bodies use them as longterm storage. One gram of oil or bacon grease, etc will provide about 9 (kilo)calories worth of energy – as opposed to say a gram of protein, which only provides about 2.5. Starches are about 3, and sugars are about 4.

Things like water and cellulose (the cell walls of plants) can’t be turned into glucose at all, so something like a stick of celery, which is almost nothing *but* water and cellulose, has approximately fuckall calories in it.

Depending on how much of what kinds of components a food is made up of, it’ll have a different total number of calories.

A calorie is the amount of energy required to increase the temperature of one ml of water by one degree Celsius.

When you start talking dietary calories you’re actually talking about kilocalories. Which means one dietary calorie is actually 1000 calories in the scientific sense.

Calories are one way to measure how much energy your body is outputting. For example walking a mile on flat ground for the average person takes about 50 dietary calories. Being alive takes calories too, with the *average* person burning about 1300 calories just by being alive for 24 hours. Now there’s a lot of variation to all of these which is why I say average. If you’re big and weigh a lot then obviously it takes more energy to move you. So you’d burn more calories from exercise than a small person. Exactly how many is next to impossible to determine precisely but these exercise guides that tell you doing x at y weight burns z calories are all a ballpark number.

There’s also calories in food. If we talk the raw chemical energy food has insane amounts of energy. But obviously we don’t convert food to energy at 100% efficiency. Pee and poop are food stuffs that haven’t been converted to energy. Everybody’s guts are different and extract a different amount of energy from food. The amount of energy that’s able to be extracted from food is called bioavailability. There is an average that everyone is near. So when you see an apple is 60 calories that means an apple has 60 calories bioavaila ible to the average person. Some people it might be 55 some people it might be 65. But it’s *around* 60.

Obviously produce isn’t 100% uniform. Each apple is different just like each person so it’s all a close estimate.

None is exact, but it’s all pretty close.

Anyway how this all relates to fat is that your body will use excess calories and turn them into fat, hair, muscle, etc.

Being able to pack on fat *was* a great thing. Evolutionarily. Because up until about 100-150 years ago it was just a fact of life that sometimes there wouldn’t enough food. And if you didn’t have any fat on your body you might starve. But in our modern lives of abundance we eat too much and it becomes a problem.

There’s something to be said about nutritional needs vs caloric needs. So cheap food might meet your caloric needs but not all your vitamin needs and so despite having too many calories you could still have health problems related to not eating enough of the correct stuff. But that’s a whole other bag of worms.

>What are calories? Is it the amount if energy in a food?

You’re spot on with this. One calorie is defined as the energy needed to raise the temperature of one gram of water by one degree C. A Calorie (yes the capitalization makes a difference) is equal to 1000 calories, or one kilocalorie. 1 Cal = 1 kcal = 1000 cal.

>How does the body uses calories, burns calories

Generally, most of the calories you use are consumed simply by existing. Involuntary actions, such as breathing, your heart beating, or conscious actions, such as walking, orr turning your head, or moving your fingers also burn calories.

>how does excess calories becomes fat?

Of the three main sources of calories the human body uses, fat has the highest energy density, or calories per gram. So our body takes any excess calories and turns them into fat for storage and use later.

>Why are food “low in calories” good for you? Why are food of the same size, have different amount if calories?

The physical size of a food as compared to a other doesn’t have an effect on the Calorie content. It has to do with the composition of ingredients in the food. Foods that are low in calories are beneficial for people that are trying to lose weight because they physically make you feel full, but you get much less calories from your food. This will force your body to collect the energy it needs from within rather than an external source.