How Your Body Burns Calories

And How Different Factors Affect It

My wife recently got me a mug that reads, “This coffee is almost as strong as my opinions.” In that spirit, I’m going to get science-y and tell you about calories. Specifically, how your body burns them. I often compare calorie management with financial budgeting because the principles are exactly the same:

• You gain by having more coming in than going out

• You lose by having more going out and coming in

• Small contributions either way add up over time

Why do I love my new mug so much? I cannot stand misinformation, especially in a world like fitness, where so many influencers make things up for views. If someone has ever told you, “Calories in vs. Calories out is old science and not true,” they probably say the same about gravity. If someone says, “Well, calories in vs. calories out didn’t work for me, so its fake,” then there are two possibilities:

1. This person is the first natural being to defy the first law of thermodynamics.

2. They didn’t count correctly.

If you’ve tried and failed, take heart! Math is hard (coming from an engineer). Additionally, just because something is simple doesn’t make it easy. That’s why I’m elaborating on how this energy is spent today, and hopefully, this knowledge empowers you to try again!

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Our term of the day is Total Daily Energy Expenditure (TDEE). As a number, it is the total calories you burn daily. As a term, it represents four factors of energy expenditure, which I have listed below.

TDEE with factors and their percentages

Basal Metabolic Rate (BMR)

Comprising at least half of your total daily calories, BMR can be thought of as the “bare minimum” your body needs to do to live. Think organ function—breathing, blood pumping, brain function, etc.- contribute to your BMR. A known way to increase BMR is by carrying more muscle mass, which is a big enough topic to be its own blog post someday… But for now, it’s good to know that muscle tissue, even when inactive, burns calories.

Thermic Effect of Food (TEF)

TEF is the energy your body spends when consuming food. This sounds great; only the burn is limited to 5-10% of total ingested calories. A quick fact about this is not all calories burn equally.

• Sugars burn like gasoline - quick to ignite and quick to go away, making them the easiest to overconsume

• Carbohydrates burn more like kindling—steady for a time but run out before too long. Simple carbs (White flour products) are closer to dry leaves, whereas Complex carbs (Whole grain products) are like good sticks and small branches.

• Protein is the giant log that will keep the fire going for an hour or better. Due to its complex structure of amino acids, which have to be broken down one by one, protein is the champion of long-lasting calories.

Physical Exercise (PE)

The most well-known method of calorie burn is also often the worst. Unless you train at a very high intensity, chances are this will amount to 10% or less of your daily burn (and that only includes training days; it’s a big ole goose egg on your off days)

Non-Exercise Activity Thermogenesis (NEAT)

(Someone really just wanted this acronym to say the word “neat,” but that’s okay.) NEAT refers to all activities not included in a workout routine. This includes walking around in the store, taking the stairs, moving grandma’s couch (contrary to popular opinion), and even things as small as fidgeting at your desk. Comprising a whopping 15-25% of your TDEE, this is another great way to burn additional calories.

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If you’ve made it this far, thank you for reading Thinking Fitness! If you enjoyed reading, please consider sharing this blog with a friend or family member. Until next time, remember that the path to success is repetitive and boring. Stay focused, and “churn that butter” on whatever path you walk!