The Science Behind a Slower Metabolism

It’s a tale as old as time: Person wants to lose weight. Person starts eating less. Person loses weight.

Person then stops losing weight and gets frustrated. So person returns to eating normally. Person gains back weight (along with a few extra pounds). And person (again) wants to lose weight…

What happened there?

The term “metabolic damage” or the more dramatic “starvation mode” often gets thrown around to describe it. I prefer to call it “metabolic adaptation” because that is what it is; your body is adapting and doing what it needs to do in order to stay alive.

Sorry to break it you; your body cares more about you being alive than you having a six-pack.

Today I want to give you a simple breakdown of what's actually going on behind the scenes. What causes this “slow metabolism” phenomenon?

Let's start at the beginning:

What is metabolism?

Metabolism is a term used to describe all the chemical reactions and physiological processes involved in using the energy from the food you eat to maintain the living state of your cells and your body.

The amount of energy (aka calories) that your metabolism requires is called the Total Daily Energy Expenditure (TDEE) and it depends on 3 main things:

Resting energy expenditure (REE)

REE represents the calories burned at rest; in other words, it’s the energy you would need if you just stayed still and did not do anything (not even eat) all day. It entails the energy needed to maintain your body temperature, keep your organs functioning, keep your blood flowing, etc.

The REE accounts for about 67% of your TDEE and is largely dependent on things like genetics, sex, age, body composition, and body size.

Thermic effect of food (TEF)

The TEF describes the calories required to digest and absorb your food.

Each macronutrient (carbohydrate, fat, and protein) takes a different amount of energy to process, but on average, 10% of our TDEE is spent just on digesting!

Physical activity (PA)

Physical activity typically represents around 23% of people’s total energy expenditure and it can be broken down into two components:

Exercise activity thermogenesis (EAT)

EAT refers to any intentional exercise you do (running, weightlifting, dancing, etc) and is of course highly variable from individual to individual.

[PS: The acronym is hella misleading]

Non-exercise activity thermogenesis (NEAT)

NEAT encompasses the physical movements in your day that aren’t purposeful/intentional exercise. It includes things like vacuuming, fidgeting, cooking, getting the mail, etc. This component is also highly variable but accounts for about 10-15% of your TDEE.

What changes when you lose weight?

When you start restricting calories and lose weight, pretty much every element of your TDEE gets affected:

As a consequence, the amount of calories you need just to maintain your weight decreases. What was a once a calorie deficit that allowed for weight loss is no longer a deficit, and weight loss stalls.

The take-away here is that extreme calorie-restriction in the name of weight loss is typically not a successful endeavour for most people in the long run.

Instead of cutting calories and worrying about reaching a certain number on the scale, simply try to add more nourishing foods into your diet. You know what these things are: veggies, fruits, whole grains, healthy fats, and lean proteins.

Doing so will add more to your life and health than dieting ever will!

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Stay nourished my friends,

Robena