Calories, Carbohydrates, Protein, Fat, and What They Do For You

I think it’s totally cool that our bodies just take food that we give it, whatever that food might be, and sort it out, sending different bits to different places in order to power our bodies.  As I continue to learn more about what to eat before/during/after exercising, I wanted to take the time to really understand what calories, carbohydrates, protein, and fat are and what they do for my body, hence this post, which I hope you will find illuminating.

what occupied my brain when I first learned all of this stuff

Some of this might be 3rd grade science type stuff, but you know what? 3rd grade science was a long time ago and I was too busy deciding how I wanted to write my name to remember what Mrs. Mason said about proteins.

What I seek to do through this post is talk about food as fuel and what it does for our bodies. First off, I’ll write about calories and what they mean when we’re talking about nutrition. Then I’ll write a bit about Carbohydrates, Proteins, and Fats, what they do, and why you need them.

As always, this is Googled Science – I think it’s all correct, and wouldn’t post it otherwise, but would like to remind you that I am an English major and not a Blogger MD.

What are Calories?
As you remember from grade school, calories are a measure of energy, and when we’re talking about food, they represent the amount of energy stored in a food. 1 gram of fat provides 9 calories of energy, 1 gram of protein provides 4 calories of energy, and 1 gram of carbohydrates provides 4 calories of energy. The overall number of calories in a food item is based off of that formula. See?

Cal = 9(g of fat)+4(g carbs)+4(g protein)
Cal = 9(2.5)+4(27)+4(5)
Cal = 22.5+108+20
Cal = 150.5

Okay, so I suppose that the 0.5 is negligible. Cool, huh?

While calories are often times the first thing examined on a nutrition label, they don’t really represent the nutritional substance of the food. The number of overall calories in something only tells us how much energy the food provides—it doesn’t tell us where the energy comes from or what the energy will do for us.

The items listed under each of the bold items are types of the bolded item. i.e. under fats, you see the types of fats. Under carbs, you see the types of carbs.

Carbohydrates
Carbohydrates are the most easily processed form of energy for your body. They are broken down into glucose (sugar) relatively quickly, and thus provide quick energy. Any of this energy that isn’t immediately used by your body, gets stored in your muscles and liver in the form of glycogen, which acts as an energy store for future uses (read: exercise). Once energy stores are full (we can store about 15g of carbohydrates per kilogram (2.2lbs) of weight), extra sugar gets stored as fat.

it makes sense that all of the carbs in an energy/sports drink comes from sugar, huh?

As you probably know, there are different types of carbohydrates. You’ll see on the nutrition label that sugar and fiber are both listed under the Carbohydrates heading. Sugars yield quick energy because your body doesn’t have to do as much work to turn them into glucose. White grains (white bread, white rice, pasta, etc) have been already been processed and are much more easily turned into sugars than their unprocessed counterparts. This is good, because they offer faster energy, but not good, because they don’t offer sustained energy in the same way that their more natural, fibrous counterparts.

I just learned that white rice is just rice that has had the husk, bran, and germ removed before being polished. It’s crazy that we take out all of those nutrient-giving-things in order to make rice prettier and have a longer shelf life (the bran has oil (fat) in it, which can spoil).

Complex, unprocessed carbs take a bit longer to break down and offer energy at a slower, more sustained rate. Our bodies break the complex carbohydrates into starch, which becomes glycogen/sugar, and fiber, which we cannot turn into energy. Insoluble fiber aids with digestion and soluble fiber slows the process of turning food into sugar, so both helps to regulate blood sugar and keeps us satiated.

I am learning SO MUCH today!

If we don’t have enough carbohydrates for energy, of course we can get energy from proteins and fats (they both have calories/energy, too), but, especially for athletes and those who need a lot of fuel, carbs represent the most easily accessible form of fuel. Also they’re delicious.

Protein
We’re made of protein (seriously – muscles, bones, tissues, tendons, hair, skin are all protein structures). Protein is how our body keeps itself operating, in terms of details like keeping our brain working and our cells (and muscle cells) regenerating. While our bodies are about 45% protein, we don’t store protein in the same way that our muscles can store carbohydrates, and the protein that is in our bodies isn’t ideal for fuel sources (I don’t want to power my body with the stuff that helps with brain function or muscle repair). Google tells me that it is important to ingest protein in order to replace the proteins that are constantly being destroyed. When we eat protein, it is broken up into amino acid which go around the body & do their thing.

We actually don’t need to eat as much protein as is commonly thought—the rule is about 0.8 to 1 gram of protein per kilogram of body weight – we can only digest a certain amount of protein at any given time. Extra protein that doesn’t go towards amino-acid type action either gets stored as fat, used as energy, or “expelled,” I suppose, is how I’ll say it. We do need normal amounts of protein regularly, though.

It takes the body more effort to turn protein into energy, so it’s not an awesome fuel for exercise. Plus, if you use protein as fuel for exercise, there will be less protein hanging out in your body to help repair your muscles post-workout. So it’s important stuff for body functioning, but not for really powering our bodies.

Fats
Fats are good for us—we need to eat healthy fats in order to do a bunch of stuff, like power our heart, lungs, eyes, and brain, keep cells flexible, keep our immune systems strong, and insulate, protect, and cushion our organs and nerves. Fats digest slowly, so keep us satiated for longer, and also allow more time for nutrients in food we eat to be absorbed. Like everything, we need fat in moderation. And it’s best to avoid the kind of fat that isn’t naturally occurring.

As you can see on the oatmeal nutrition label, there are 4 different types of fats. The unsaturated fats (both poly & mono) are found in fish, plant oils, nuts, etc and are generally called the “good fats” because they lower cholesterol and are, well, good for you (in moderation, of course). Trans fats are the ones that are completely man made, funky weirdo things that occur when hydrogen is added to vegetable oils (thereby partially hydrogenating them) to make them more stable and longer lasting (i.e. for the benefit of infinite shelf life). Everyone, particularly  Denmark, Switzerland, New York City, and Arnold Schwarzenegger, agree that trans fats are no good and should be avoided. They do bad things to cholesterol levels and are just funky food.

There are mixed thoughts re: saturated fats, which are found in animal products (meat, milk products, etc). There seems to have been an improperly conducted study in the 50s that suggested a high correlation between saturated fat and heart disease/artery clogging/cholesterol level. More recent studies, however, suggest that saturated fats aren’t as bad as they have been thought and that the “study” done in the 50s never actually showed anything. This Men’s Health article has more on why saturated fats aren’t all that bad. My thought is that they’re naturally occurring and people have been eating them forever, so like everything, they are just fine in moderation.

Fat provides the densest form of energy – after all, 1 gram of fat has 9 calories of energy, verses the four calories of energy in 1 gram of a carbohydrate or a protein. While we have a limited store space for carbohydrates and protein, we can, as is obvious, store almost an endless amount of fat on our bodies, but doing so is obviously not ideal. Obviously. Turning stored body fat into energy takes time and requires a lot of oxygen. Long lasting exercise at a low to moderate intensity is fueled by fat, but even during high intensity exercise when your body is quickly burning through stored carbohydrates, fats aid in that glycogen-to-energy process.

What to take away?
All right, so there is a ton of information here (and my brain is exhausted), but I think the overarching important theme is that we need to eat all of these nutrients in moderation in their naturally-occurring forms in order to function most effectively. That makes sense, since that’s what cavemen did.

Hopefully understanding what carbohydrates, protein, and fats offer to our body will help us see food as fuel and science and continue to make wise and well-educated food choices!

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7 Comments to “Calories, Carbohydrates, Protein, Fat, and What They Do For You”

  1. Thanks so much for posting this. I learned a lot. I love your writing style. I wish it could be a source of income as well as happiness and education for you!

  2. Thanks, Sarah! I agree with Lara…I’m learning so much reading your blog.

    I do have one question, though. Do you have a formula for figuring out how much protein we need? I know less than nothing about converting metric to American measures and back. But I’d like to know how much protein I should be aiming for in my daily intake.

    Thanks again. Keep ’em coming!

    • yup! it’s about 0.8 to 1 gram of protein for every kilogram (2.2 pounds) of body weight. For people who are doing crazy amounts of muscle work/exercise, that number is increased, but doesn’t need to ever be higher than 1.8g of protein for every kg of weight.

      I’m learning so much from writing this blog! glad it’s helpful 🙂

  3. love this post! learned/relearned several things:~)

    but don’t forget the other calories – alcohol. that’s about 6kcals/g, iirc. what i considered the biggest flaw in the new points plus plan at weight watchers is there is no way to calculate the points of food containing alcohol yourself. this impacts not just beer & the other obvious beverages, but foods sweetened with sugar alcohols. okay, there’s my WW pet peeve, lol.

    & i was just telling my dad that about brown rice last night.

    thanks especially about the diff types of fiber. that always confuses me, & i’ve never fully understood the difference.

    also good to know about how the whole “fat burning zone” thing in exercise works. i’ve heard a lot about how to get there, but that’s the first time i’ve seen the how & why of it to where it makes sense. yay!

  4. Extremely information! I have already been trying to find something similar to this for a long time now. Appreciate it!

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