What a Calorie Actually Is, Why “Good” and “Bad” Calories Don’t Exist, and How to Actually Calculate Your Numbers
After a string of conversations with people outside the fitness world, one thing became clear: calories are one of the most misunderstood concepts in health and nutrition. This post clears it up — what a calorie actually is, where the confusion about “good” and “bad” calories comes from, and the practical math behind building muscle or losing body fat.
Spoiler alert: there’s no such thing as a good or a bad calorie. There’s also no such thing as a “different kind” of calorie. But there’s plenty of real confusion underneath those myths, and it’s worth untangling. Watch the episode below, or read the abridged transcript.
Chapters:
00:00 Introduction
01:40 Definition of Calorie
03:52 Good and Bad Calories?
10:06 Different Kinds of Calories?
10:32 Macronutrients – Calories vs. Net Calories
14:47 Practical Considerations: The Calorie Balance Equation
17:37 Practical Considerations: Calorie Burning Confusion
20:19 Practical Considerations: Estimating Intake, Output, and Monitoring Progress
What Is a Calorie?
A calorie (lowercase c) and a Calorie (capital C) are both units of energy, and they’re related.
One calorie (lowercase c) is the amount of heat needed to raise one gram of water by one degree Celsius. The calorie was originally part of the metric system — it’s since been phased out in favor of joules, but the metric-system roots are why the math lines up so cleanly: one gram of water is one milliliter of water, and everything scales together.
One Calorie (capital C) is also known as a kilocalorie, because it’s equivalent to 1,000 lowercase-c calories. Using the definition above, a kilocalorie raises one kilogram of water by one degree Celsius — again, one liter of water. Clean and consistent, by design.
The kilocalorie (capital-C Calorie) is the unit used on food labels. That’s what “calories” means for the rest of this post, since the lowercase-c version is too small a unit to be useful for food. Fun fact: when Powerade first launched to challenge Gatorade, the label listed calories as “energy” in parentheses. That’s not wrong — a calorie is simply a unit of energy, nothing more.
Good Calories, Bad Calories? They Don’t Exist.
Calories are amoral. They’re just energy. Nobody would argue that a degree Celsius is “good” or “bad” — it just is. The same logic applies to calories. But we assign morality to them anyway, and that’s where the phrase “empty calories” comes from.
That phrase is really about a different distinction: calorically dense foods versus nutrient-dense foods.
Nutrients are what food breaks down into — what your body uses for digestion, energy, and countless other processes. There are two categories: macronutrients (protein, carbs, fat, and alcohol — more on those below) and micronutrients (vitamins and minerals), which your body needs to survive.
Calorically dense foods pack a lot of energy into a small volume, without much nutritional value to go with it. The go-to example: a deep-fried Twinkie. It’s small, but by the time it comes out of the fryer it’s essentially a dense ball of grease — no vitamins, no minerals, all artificial chemicals and deliciousness. That’s the textbook “empty calorie” food: pure energy, no nutrition.
Nutrient-dense foods let you eat a much larger volume for the same number of calories. A few years back, the plant-based movement popularized the claim that broccoli contains more protein than steak. On a per-gram basis, that may be true — the graphic making the rounds claimed 300 grams of steak had 9 grams of protein, versus 10 grams for 300 grams of broccoli. But 300 grams of steak is a modest 10-ounce New York strip — not exactly a filling meal on its own. 300 grams of broccoli is roughly 1.8 cups, chopped. So even if the protein numbers are close, you’re eating a lot more food, by volume, to get there.
That’s the real distinction: nutrient-dense food lets you eat more food for the same calories as a smaller portion of something calorically dense. As an example, one of my go-to meals — two cups of white rice, a handful of spinach, 10 ounces of grilled chicken, and half an avocado — looks like a huge plate of food, but it’s roughly 980 calories. A double bacon cheeseburger runs somewhere around 750–800 calories: far fewer calories, but a fraction of the volume.
None of this makes calories “good” or “bad.” It’s just useful to know what’s actually in the food you’re eating — and how much of it you get to eat.
One more example: a nutrition client of mine had cut out all salad dressing because she’d decided olive oil was a “good fat,” and was dressing her salads with straight olive oil instead — lunch and dinner. A standard serving of olive oil is about a tablespoon. She was using roughly six tablespoons per salad, twice a day. Do the math, and that’s roughly 1,200 calories a day from olive oil alone — from something she believed was helping her, simply because it had been labeled “good.”
Where the Real Confusion Comes From: Macronutrients
There are only two kinds of calories: lowercase-c and capital-C, and one is just a multiple of the other. So why does it feel like some calories “count differently” than others? Because people are actually talking about macronutrients — and specifically, how much of what you eat your body actually absorbs.
Each macronutrient has a different caloric value per gram:
| Macronutrient | Calories per gram |
|---|---|
| Protein | 4 |
| Carbohydrates | 4 |
| Fat | 9 |
| Alcohol (the 4th macronutrient) | 7 |
Fat containing more than double the calories per gram of protein or carbs is part of where the “fat is bad” myth got its start.
The Thermic Effect of Food
This is the piece most people miss. The thermic effect of food is the energy your body has to spend to extract energy from what you eat — you have to burn calories to get calories. It’s often filed under “calories out,” but I’d argue it belongs under “calories in,” since it directly affects how many of the calories you eat actually get absorbed.
The more fibrous or difficult a food is to break down, the more energy it takes to extract its calories — which means your net calories absorbed end up lower than the label suggests:
| Macronutrient source | Calories absorbed per 100 eaten |
|---|---|
| Protein (tough source, e.g. venison jerky) | ~70–85 |
| Protein (easily digested, e.g. whey) | ~85 |
| Carbohydrates | ~90–95 |
| Fat | ~97–100 |
Fat takes almost no energy to break down — which is also why it’s so easy to convert dietary fat into stored body fat when you’re eating in a surplus. That’s the root of the low-fat movement, which turned out to be a wrong turn for different reasons.
So when people say “all calories aren’t equal,” what they’re really observing is that net absorbed calories differ by macronutrient source — not that the unit of energy itself changes. If you increase your protein intake and hold total calories steady, you may see a small amount of weight loss, simply because you’re absorbing a smaller share of those calories thanks to the thermic effect of food.
The Calorie Equation: Calories In vs. Calories Out
At its core: calories in − calories out = change in body stores. This is the first law of thermodynamics, and it isn’t optional. Wanting to override it is a bit like wanting to fly — it doesn’t matter how badly you want it, physics doesn’t bend.
One pound of body fat is roughly 3,500 calories. A commonly recommended daily deficit is 200–500 calories. At a true 500-calorie daily deficit, you’d burn through 3,500 calories — one pound of fat — in a week.
Calories in is actually your calories absorbed: calories eaten, minus what’s lost to the thermic effect of food (see above).
Calories out is where most of the confusion lives. It has three components:
- Basal Metabolic Rate (BMR) — the energy your body burns just to stay alive: every essential function running in the background, even if you spent all day in bed.
- NEAT (Non-Exercise Activity Thermogenesis) — everything that isn’t purposeful exercise: fidgeting, pacing while you’re on the phone, and generally, light walking. This is why daily step count matters.
- Exercise — purposeful training.
Two things make “calories out” hard to pin down. First, BMR and NEAT are both difficult to estimate accurately, and no two people are the same. Second, your body adjusts. As you lose weight, your BMR drops — meaning a deficit that worked last month may not be a deficit anymore.
An extreme example makes this easy to see: an anorexic teenage female in a severe caloric deficit will often lose her ability to menstruate. That’s the body diverting energy away from a non-essential function (reproduction) to protect the essential one (staying alive). In less extreme but still significant deficits, men often lose their sex drive, and both sexes can see degradation in skin, hair, and nail quality. Your body is deprioritizing anything that isn’t required for survival — including, eventually, your own drive to move around. You fidget less, you walk less, and your metabolic rate slows. All of that quietly erodes the deficit you think you’re in.
Exercise trackers don’t help much either — they tend to overestimate calories burned, and different devices routinely disagree with each other by wide margins. If none of these numbers can be fully trusted, how do you figure out whether you’re actually in a deficit?
You start by estimating your maintenance calories.
How to Estimate Your Maintenance Calories
Even the “calories in” side of the equation is an estimate — food labels are commonly cited as having up to a 25% margin of error, largely due to variability in how food is processed and packaged (water-cooled vs. air-cooled chicken, for instance, can hold different amounts of water, which throws off weight-based measurements). The nutrition facts themselves are accurate for what’s actually in the food; the challenge is knowing exactly what that is once it’s on your plate.
Since neither side of the equation is exact, the goal is a solid estimate you can then adjust based on real-world results. This is the same basic method apps like MyFitnessPal use to generate your starting maintenance number before applying a deficit or surplus.
Step 1: Start with an exercise multiplier (10–22).
- 10 — no purposeful exercise
- 12–13 — a casual exerciser doing about an hour of purposeful exercise, five days a week (use 12 if it’s strength training with rest between sets; use 13 if it’s continuous activity like the elliptical, since you’re working the entire hour)
- 22 — a professional athlete training 5–6 hours a day, multiple days a week (think Olympic-level swimmers or CrossFit Games athletes)
Step 2: Add a NEAT adjustment based on daily steps.
| Daily steps | Add to multiplier |
|---|---|
| 0–5,000 | +0 |
| 5,000–10,000 | +0.5 |
| 10,000–15,000 | +1 |
| Extremely active | up to +2 |
Step 3: Multiply by body weight.
Example: a 200-lb male doing an hour of strength training five days a week (exercise multiplier: 12) and averaging roughly 10,000 steps a day (NEAT adjustment: +0.5) lands on a combined multiplier of 12.5. Multiply that by his 200-lb body weight, and his estimated maintenance is roughly 2,500 calories per day.
That number is a starting estimate, not a verdict — which is why the next step matters just as much.
Monitor the Scale — Not Day to Day, but Week to Week
Once you’ve set a target based on your estimated maintenance, the scale tells you whether the estimate was right. Weight will fluctuate daily based on sodium intake, sleep, and — for women — where you are in your menstrual cycle. That’s normal, and it’s why day-to-day numbers are noisy. Track the trend over a week or more instead.
- If you’re in a genuine deficit, the trend line moves down over time.
- If you’re in a surplus, it moves up.
- If nothing moves and you’re supposed to be in a deficit, your estimate was off — usually because actual BMR, actual steps, or actual exercise time came in lower than assumed. Adjust intake down by roughly 200 calories a day and watch the trend again.
The downside of scale-tracking is that people can fixate on it. Try not to. It’s one data point, not a verdict on your worth or your progress. How your clothes fit and how you feel matter too.
Why You Can’t (and Shouldn’t Try to) Lose Weight Indefinitely
Because BMR drops as you diet, a deficit that works today eventually stops working if you stay in it too long — and your body isn’t designed to shed weight forever. As a rule, don’t try to lose more than about 10% of your body weight in a single stretch; pushing past that is where metabolic damage becomes a real risk.
A reasonable cadence: about 12 weeks in a deficit, then 8 weeks at maintenance to let your BMR recover (you’ll often find you can eat somewhat more than you expected and still hold your new weight). Repeat the cycle if you have more to lose.
It’s also worth naming the obvious: you can’t diet forever. Taken to its logical extreme, an indefinite deficit would trend you toward zero pounds — which is exactly why the idea falls apart. We’re also biologically wired to regain weight over time; our hunter-gatherer ancestors survived cycles of feast and famine by holding onto stored energy whenever it was available. Extrapolate that instinct over a modern lifespan, and gradual weight gain over the years starts to make a lot more sense. Regular scale monitoring — without obsessing over it — is how you catch that drift early.
The Bottom Line
There’s no such thing as a good or a bad calorie — it’s just a unit of energy, and all calories are equal. What isn’t equal is how much of what you eat your body actually absorbs, which depends on the macronutrient and the source.
Both sides of the calorie equation are estimates. Calories in is hard to pin down precisely, and so is calories out. The only real path forward is to start with a solid estimate, track consistently, and let the scale trend tell you whether to adjust. Hormones and other factors matter too, but they’re part of the same equation — not a replacement for it. Anyone telling you calories don’t matter is missing part of the picture. We can’t override the laws of physics.
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