Wait, what is a calorie?

So, what is a calorie and why is it so important to lose weight? Let’s start at the very beginning.

All successful diets are based on the principle of Calories In vs Calories Out. Yes, even if it’s keto, paleo, low carb, weight watchers, or any other method of weight loss out there.

But hold on, what even is a Calorie, and why is it important to weight loss?

A calorie is a measure of energy.

What does that really mean? It means that all food (literally everything edible) has energy in it. Calories tell us exactly how much energy is contained in a food.

For example, my favorite chocolate chip cookie has 250 units of energy or calories. Energy I will spend running around my office, walking on the treadmill, and doing dishes after dinner.

And just like I fill my car’s tank with gas in order to get where I need to go; I have to put the proper amount of fuel in my tank for my daily expenditures.

For every second that we are alive, our bodies are using energy or burning calories. If you lay in bed all day, your body still needs energy to run your brain, pump your blood, and even breathe. The amount of energy or calories burned at rest is called your Basal Metabolic Rate [BMR].

As your level of activity increases (meaning you go to work or run a mile), the amount of energy burned or calories burned goes up.

We are able to estimate how much energy or calories your body burns over the course of a day by calculating your Total Daily Energy Expenditure or TDEE. This number includes calories burned from all of your daily activity and exercise. Calculators like this one are pretty accurate as long as you are realistic about your lifestyle.

I am 29 years old, 5’6″, and currently at 160 pounds, so my BMR is 1,467 and my TDEE for sedentary (which I really am, even on days I workout) is 1,761.

More numbers? Let’s slow down.

Why is your BMR and TDEE important for weight loss? Ultimately, it is a very simple equation. You take the amount of calories you’ve eaten for the day, and subtract the amount of calories you have burned. Whatever is left will dictate whether you are in a calorie surplus, deficit, or maintenance state.

Calories eaten – Calories burned = Energy state

Let me put it this way. If I laid in bed all day and ate 1,467 calories (or just under 6 chocolate chip cookies), I would not gain fat or lose fat (ie. weight). I would burn all the calories I ate for the day.

1,467 calories – 1,467 calories = 0 calories [maintenance]

If we eat the same amount of energy we burn in the day, we are in a maintenance state.

If I laid in bed all day and ate 1,761 (or seven chocolate chip cookies), I would gain fat. Because I would have calories left over at the end of the day that were a surplus. My body, being very smart and concerned with living through famines, will save those calories for later in the form of fat.

1,761 calories – 1,467 calories = 294 calories [surplus]

If we eat more energy than we burn in the day, we are in a calorie surplus.

Our bodies save that energy for later in the form of fat and we “gain weight.” Does it work the opposite? Yes, yes it does, and thank goodness for that.

If I burned 2,000 calories in the day (after factoring in my walking, energy burned at the gym, etc.) and ate 1500 calories for the day, my body will need to tap into my reserved energy (or fat) to get those calories.

1,500 calories – 2,000 calories = -500 calories [deficit]

If we eat less energy than we burn in the day, we are in a calorie deficit.

It’s really that simple. If you eat more calories than you burn, those will be stored as fat and you will gain weight. If you eat fewer calories than you burn, your body will tap into that stored fat to use as energy, and you will lose weight.

Well, the concept is simple, but the application can be very challenging. Hence why you see so many different styles of eating (all with their own claims). But at the end of the day, they are just a form of eating fewer calories, whether they eliminate whole food groups (keto) or assign a different unit of energy measurement (Weight Watchers).

It all comes back to calories in vs. calories out.

If you are looking for ways to count calories, where to start, and other tips and tricks, check back next week! My next post will be covering Calorie Counting how-tos!