The Math of Losing Weight / How To Count Calories

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This is a very important post, guys.

When I was finishing up my degree in mechanical engineering at Texas A&M (Whoop!), one of my favorite classes was Thermodynamics. I remember on the first day, my professor gave his introduction slideshow, and one of his bullet points said something along the lines of:

  • Thermodynamics will change the way you look at life.

Diet Thermodynamics

As a know-it-all 20 year old student, I laughed a little. That was a DRAMATIC bullet point. Wow, this class is gonna CHANGE MY LIFE! Hah, yeah, right.

But, it kind of did – because believe it or not, dieting and losing weight follow the laws of thermodynamics; namely, the energy balance concept.

Basically, our bodies run on energy. That part is obvious, right? We get that energy from consuming food and drinks. And our fat stores are just our body’s way of keeping extra energy.

Our bodies literally run on energy.

Therefore, when we burn more energy than we consume, our body has no choice but to take some energy from our fat stores. On the other hand, if we consume more energy than we burn, our body is going to keep that extra energy (usually converting it to fat).

That energy is usually measured in calories. You know, those numbers you see on the back of your Pop Tarts.

Check it before you wreck that Pop Tart. 200 calories each.


Let’s say, for example, that your body burns about 2000 calories a day (your “daily maintenance calories“). That means three things. We’ll call them the 3 Laws of Pop Tarts:

  1. When you eat 10 Pop Tarts (2000 calories), you will stay approximately the same weight.
  2. When you eat 11 or more Pop Tarts (2200+ calories), you will gain weight.
  3. When you eat 9 or less Pop Tarts (1800- calories), you will lose weight.

Obviously, nobody eats 10 Pop Tarts a day and this is an oversimplification. Maybe you have the body of Arnold Schwarzenegger, whose body burns over 4000 calories a day. Maybe you’re more of a Homer Simpson, sitting at a desk job all day with a body that burns closer to 1800 calories a day. But the principle is the same:

You will lose weight if you consume less calories than you burn.

Okay, so how do I start?

First, start using a calorie counter such as MyFitnessPal and record what you eat every day. Every Pop Tart you eat, log it on your calorie counter.

Second, if you eat a lot at home, I highly recommend buying a kitchen scale and weighing your food. This way, you eliminate all guesswork involved in estimating your portion sizes.

Third, figure out your daily maintenance calories. This is unique to each individual person, but you can get a quick estimate using a calculator like this one.

Last, figure out what your daily calorie limit will be.

Quick rule of thumb: one pound of fat is equal to about 3500 calories (MayoClinic).

That means if you eat 500 calories less than your daily maintenance calories, you should lose 1 pound (7 days x 500 calories per day = 3500 calories) a week. If you eat 1000 calories less than your daily maintenance calories, you should lose double that amount (2 pounds) per week.

It’s not recommended that you try to lose more than 2 pounds a week. That’s how crash diets that don’t last long term work. Be realistic.

This is the principle that helped me lose over 50 pounds in the past few years, and it’s the principle I still follow today. It really is that simple.


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