Calories are a unit of measurement for calculating energy gained by eating food. We then expend energy from calories through physical activity. Consuming more calories than you use in a day causes you to gain weight, while consuming fewer causes you to lose weight. The math is quite simple, but there’s a lot more to the lowly calorie than you might think…
A Quick Note: The data presented in this article get’s wonky on some mobile devices. Sorry.
In This Article
- More Than You Ever Wanted To Know About Calories
- How Many Calories Do We Need?
- How We Use Calories
- What Are ‘Bad’ or ‘Empty’ Calories?
- How To Avoid Inefficient Foods
- What Does All This Mean?
- My Advice
- Calories: The Takeaway
More Than You Ever Wanted To Know About Calories
First, let’s get some boring (interesting to me) science details out of the way. There are actually two types of calories: small and large.
One small calorie, or cal, is the amount of energy required to raise the temperature of one gram (1g) of water by one degree Celsius (1°C).
One large calorie, or kcal (short for kilocalorie), is the amount of energy required to raise one kilogram (1kg) of water by 1°C.
If you’re familiar with the metric system, you probably already figured out that one kcal is equal to one thousand calories.
For my fellow ‘Muricans out there, here are some quick conversions (you’ll probably need these later):
1kg = 1/4 U.S. gallon or 1 liter
1lb = .45kg
1°C = 1.8°F
Why does this matter? Well, in the diet and nutrition world, when we talk about calories, we’re actually talking about kilocalories. That means that a Milky Way bar is technically 264,000 calories, but 264 kilocalories. Does this change any of the math for us? No, it’s just a nit-picky science detail I thought you should know. We will use the term ‘calories’ to mean kilocalories, just like the rest of the world does.
As we stated above, calories are a unit of measurement to calculate energy. For our purposes, that energy comes from food and drinks that we consume, but that’s not the only thing that provides calories. One gallon of gasoline, for example, is roughly 29,000 – 31,000 (depending on the source I found) calories.
That’s a reflection of the energy output for a gallon of gasoline, not a suggestion that you should drink it.
Please DO NOT DRINK GASOLINE hoping to get swole.
Back to important stuff.
A pound of fat is about 3,500 calories. (It’s a bit more complicated than that, but we’ll use it as a baseline for now.) This means to lose a pound of fat we need to burn 3,500 calories and to gain a pound of fat we need to consume 3,500 calories. Simple math tells us that cutting our calories by 500 each day will lose us a pound a week. 3,500 divided by 7 days in a week equals 500. The opposite is also true. We’ll get into this a bit more later.
Food is mainly composed of three macronutrients, or macros. Macros are protein, carbohydrates (carbs), and fat. These macros directly influence the number of calories a food contains. The values are:
1g of protein = 4 calories
1g of carbs = 4 calories
1g of fat = 9 calories
Let’s look at the nutrition label of a Quaker Oats Chewy Chocolate Chip Granola Bar:
As the label states, one 24g bar is 100 calories and there are 3.5g of fat, 17g of carbs, and 1g of protein.
3.5g of fat x 9 calories per gram = 31.5 calories of fat
17g of carbs x 4 calories per gram = 68 calories of carbs
1g of protein x 4 calories per gram = 4 calories of protein
31.5 calories of fat + 68 calories of carbs + 4 calories of protein = 103.5 calories total.
Why is it off by 3.5 calories? Because the Food & Drug Administration (FDA) allows for a bit of rounding.
“I CAME HERE 4 GAINZ, NOT MATH!”
You, probably…
That’s a lot of technobabble, but you’re both smart and beautiful, so I know it was a walk in the park. Also, buckle up because there’s a lot more coming. The next obvious question is “How many calories do I need?”. Unfortunately, I can’t answer that question.
Not exactly.
How Many Calories Do We Need?
Every human on the planet has different caloric needs based on their sex, age, height, weight, activity level, and a bunch of other stuff. Because of this, there is no one answer that fits everybody. Thankfully, we have some general guidelines to follow.
The numbers below reflect data from the 2015-2020 Dietary Guidelines For Americans published by the FDA in 2015. An updated version of the guidelines published in 2020, but I could not find a corresponding appendix of calorie recommendations (though after reviewing several documents, the numbers are all roughly the same).
| Men (Age) | Sedentary | Semi-Active | Active | Women (Age) | Sedentary | Semi-Active | Active |
|---|---|---|---|---|---|---|---|
| 18 | 2,400 | 2,800 | 3,200 | 18 | 1,800 | 2,000 | 2,400 |
| 19-20 | 2,600 | 2,800 | 3,000 | 19-20 | 2,000 | 2,200 | 2,400 |
| 21-25 | 2,400 | 2,800 | 3,000 | 21-25 | 2,000 | 2,200 | 2,400 |
| 26-30 | 2,400 | 2,600 | 3,000 | 26-30 | 1,800 | 2,000 | 2,200 |
| 31-35 | 2,400 | 2,600 | 3,000 | 31-35 | 1,800 | 2,000 | 2,200 |
| 36-40 | 2,400 | 2,600 | 2,800 | 36-40 | 1,800 | 2,000 | 2,200 |
| 41-45 | 2,200 | 2,600 | 2,800 | 41-45 | 1,800 | 2,000 | 2,200 |
| 46-50 | 2,200 | 2,400 | 2,800 | 46-50 | 1,800 | 2,000 | 2,200 |
| 51-55 | 2,200 | 2,400 | 2,800 | 51-55 | 1,600 | 1,800 | 2,200 |
| 56-60 | 2,200 | 2,400 | 2,600 | 56-60 | 1,600 | 1,800 | 2,200 |
| 61-65 | 2,000 | 2,400 | 2,600 | 61-65 | 1,600 | 1,800 | 2,200 |
| 66-70 | 2,000 | 2,200 | 2,600 | 66-70 | 1,600 | 1,800 | 2,000 |
| 71-75 | 2,000 | 2,200 | 2,600 | 71-75 | 1,600 | 1,800 | 2,000 |
| 76+ | 2,000 | 2,200 | 2,400 | 76+ | 1,600 | 1,800 | 2,000 |
Ladies, if you’re wondering why men get a higher average calorie allowance, it’s because men tend to have more muscle mass and muscle mass requires more energy (calories) to function. Basically, even sitting on the couch watching the game a man burns more calories (on average) than you do. This is why he can pound a couple burgers and wash it down with beer and still have a six pack.
It’s not fair, I know.
So this is all fine and good for a baseline, but as we can see, it changes depending on activity level. Obviously, a spreadsheet monkey and a construction worker don’t need the same amount of calories, not to mention athletes or other highly active people.
How We Use Calories
As we already know, calories are energy. Our body uses energy to perform tasks. This means the amount of physical activity we do, and how intense that activity is, changes the amount of energy (calories) we need. For example, let’s look at the difference between walking, jogging, or running.
Note: Your sex, age, height, weight, etc. change these numbers. The following is for a 180lb, 30-year-old man.
Walking 4kph or 2.5mph burns ~255 calories per hour.
Jogging 8kph or 5mph burns ~680 calories per hour.
Running 16kph or 10mph burns ~1,300 calories per hour.
This means that rewarding ourselves with a candy bar (our Milky Way is 264 calories) after our hour-long walk actually negates any calories we lost by walking, plus gives us about 10 more. According to the recommended calorie intake table above, a moderately active 30-year-old man needs roughly 2,600 calories a day. Does that mean he needs to run at a breakneck speed for two hours a day or risk gaining weight?
Thankfully, no.
Simply by existing, we burn calories. Pumping blood through our body, absorbing oxygen in our lungs, walking around, digesting food, and shaking our tail feather at the club all burn calories. This is known as our basal metabolic rate or BMR. Other common names are resting energy expenditure (REE) and resting metabolic rate (RMR).
We calculate this with the (revised in 1990) Harris-Benedict formula which is:
| Men | BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5 |
| Women | BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161 |
This means a 6’1’’, 180lb, 30-year-old man would have a BMR of 1825.275.
1825.275 = (10 x 81.64kg) + (6.25 x 185.42) – (5 x 31) +5
Just by living life, that individual burns roughly 1,825 calories a day. Any physical activity (walking to class, getting your ass beat by coach, crying in your shower alone) burns additional calories on top of that BMR. Remember the recommended daily intake of 2,600 calories above? That math is calculated taking into consideration the BMR (in this case 1,825) plus the assumed level of ‘moderate activity’ equaling roughly 775 calories of energy expenditure each day.
Basically, the math is trying to give us an idea of at what calorie intake we’ll gain or lose weight. In other words, if we eat less than 2,600 calories each day, we will probably lose weight, and if we eat over 2,600 calories a day, we will probably gain weight.
How quickly we gain or lose weight is obviously reflected by the amount of calories we consume. Since we know that a pound of fat is about 3,500 calories, if this individual ate 3,100 calories a day (2,600 recommended + 500 extra for the sake of this example) they would gain a pound a week (500 calories x 7 days in a week = 3,500 calories or one pound).
What Are ‘Bad’ or ‘Empty’ Calories?
We often hear about bad or empty calories in regards to certain foods, but I like to think of it more as inefficient calories. To our body, a calorie is a calorie. It doesn’t matter where it comes from. The main difference is what else comes with those calories.
Let’s compare a ~7.6oz. Big Mac with 8oz. of chicken breast.
| Data | 7.6oz. Big Mac | 8oz. Chicken Breast |
|---|---|---|
| Calories | 563 | 246 |
| Carbohydrates | 44g | 0g |
| Fat | 33g | 2.78g |
| Protein | 26g | 51.72g |
| Sodium | 1,007mg | 146mg |
| Sugar | 9g | 0g |
You don’t need to be a mathmagician to realize the chicken breast is significantly more efficient than the Big Mac. Keep in mind that’s just the sandwich, fries and soda aren’t included.
How To Avoid Inefficient Foods
The first thing to remember is that fat has double the calories of protein or carbs, so avoiding anything with a high fat content will help. Don’t avoid fat entirely, just be aware of your consumption.
Fried or processed foods should be avoided, or at least consumed in moderation. The cooking oils they use add unnecessary fat, plus they tend to pack processed foods with salt to preserve it.
Added sugars are another easy way to rack up calories. Soda, sauces, and obviously sweets are the biggest culprits. In America we love to add sugar to things, so always check the label to make sure you won’t end up like Wilford Brimley (RIP).
In general, food is healthiest in its most natural state. This means whole fruit, vegetables, and meat from ethically sourced animals that are fed their natural diet and not pumped full of hormones or other crap.
What Does All This Mean?
The next question is how do I use my knowledge of calories to gain or lose weight, depending on my goals? Well, the simple answer is math. Eating less will make us lose weight while eating more will make us gain weight. You didn’t need to read any of this article to understand that.
Unfortunately, it’s not quite that simple. (Is anything ever simple in science?)
First, it’s important to understand the difference between fat loss and weight loss. For most of us, they are the same thing. If you start cutting calories and working out but don’t notice a difference on the scale that’s not necessarily a bad thing.
Muscle weighs twice as much as fat. This means that as we burn fat and gain muscle we will likely start to look thinner, but the scale will tell us nothing’s changed. Tell that scale to go jump off a bridge. We’re still losing fat, which is the goal.
Second, keep in mind that our starting weight can drastically impact how quickly we gain or lose fat as well. If you’ve ever watched one of those weight loss competition shows you might have seen someone lose upwards of 34 pounds in a week. Meanwhile, I struggle to lose a pound a week if I’m not severely cutting. Why is this?
There are a few reasons. The first is that someone who is morbidly obese probably has a crap diet. Simply changing them to a healthy diet can cut thousands of calories off their daily intake, which will drastically help their weight loss. Second, the heavier we are, the more energy it takes to move our body. This means that heavy people actually have a higher BMR than lighter people.
Finally, and this is sort of an aside, I’d like to point you to an interesting experiment by a nutrition professor in 2010 who only ate junk food like Twinkies, Dorito’s, and Oreos but lost 27 pounds in two months. Yes, you read that right. You can eat nothing but junk food and lose weight as long as you are at a calorie deficit.
The problem becomes nutrition. Without a proper balance of macros, nutrition, electrolytes, and hydration, we will probably not be healthy. All kinds of health problems can arise, and we don’t want any of them. Eating a wide variety of whole foods and is an important part of total body health and fitness. Athletes in particular want to read every nutrition label they can find to ensure the best, most efficient balance of calories and nutrients possible to fuel their bodies without being hungry all the time.
That being said, don’t be afraid to indulge in ice cream once in a while. You did all this math; you deserve it.
My Advice
You’ve probably heard me say this before, and are maybe tired of it by now, but my advice is to experiment and find what works for you. There are so many variables to this sort of thing that no one can give you a straight answer that will work 100% of the time for every person.
Use the knowledge you’ve gained to make informed decisions and make tweaks to your eating habits until you achieve the results you’re looking for.
Or just hire me and I can do a bulk of the work for you.
Calories: The Takeaway
This is a lot to process, I know. Fortunately, the important things are pretty straightforward:
- Consuming fewer calories than you need in a day will cause you to lose fat, while eating more calories will cause you to gain fat.
- One pound of body fat is roughly equal to 3,500 calories.
- Fat (the macro) has more than double the calories (9) of protein (4) or carbs (4).
- Muscle weighs twice as much as fat.
- Weight loss and fat loss are similar, but different. Don’t take the scale’s numbers too personally.
- Always look to balance the most healthy and efficient foods you can.
If, like me, counting calories, calculating BMR, or otherwise doing math at all is worse to you than a two-week vacation to Guantanamo Bay, talk to your doctor, personal trainer, or nutritionist. They can help you zero in on a diet plan that will work for you.
Or you could just download an app like MyFitnessPal to make your life a lot easier.
Additional Links
Body Weight Planner (Cited in 3,500cal / lb article)
Nutrition Data Tool
BMR Calculator
Food Comparison Calculator
