Lesson 1: Calories and Metabolism Basics

What is metabolism?

Your metabolism is the system that manages and distributes these calories for different needs. It’s not just one thing happening in your body—it’s a collection of processes that work together to keep you alive and functioning. Let’s break it down.

1. Basal Metabolic Rate (BMR)

   This is the largest component of metabolism for most people, usually equating to 60-70% of daily calorie use. BMR represents the energy your body needs to keep basic functions running while at rest, like breathing, circulating blood, regulating body temperature, and repairing cells. Factors like age, genetics, body size, and especially muscle mass affect your BMR.

   Why Muscle Matters for Metabolism: muscle tissue is metabolically active, meaning it burns more calories at rest compared to fat tissue. While the difference per pound isn’t enormous, it adds up: more muscle increases your resting metabolic rate and makes your body more efficient at using calories.

2. Thermic Effect of Food (TEF)

   Whenever you eat, your body spends energy digesting, absorbing, and metabolizing nutrients from your food. This is TEF, and it makes up about 10% of daily energy use. Not all foods require the same energy to process, however:

   Protein has the highest TEF, about 20-30% of the calories in protein are burned off just during digestion.

   Carbohydrates use about 5-10% of calories for digestion.

   Fats use the least, only about 0-3% of calories from fat are used for digestion.

   This means high protein foods not only help with muscle repair and satiety, but also slightly increase how many calories your body burns processing them.

3. Physical Activity

   Physical activity is divided into two groups:

   Exercise Activity Thermogenesis (EAT): planned, structured activity like lifting weights, running, cycling, or fitness classes. This can make up 10-20% of daily energy expenditure, depending on how active you are.

   Non-Exercise Activity Thermogenesis (NEAT): all the movement that isn’t formal exercise—walking around at home or work, standing instead of sitting, doing chores, fidgeting, playing with your kids. NEAT can vary dramatically from person to person and can make a huge difference in calories burn. It can make up 15-50% of daily energy expenditure.

   Why is NEAT so important? Because while you might spend 1 hour in the gym, you spend the other 15 waking hours of your day moving—or sitting. Small changes like standing more, walking after meals, or choosing the stairs over the elevator can add up to a meaningful calorie burn. Having a ‘step goal’ can contribute to more daily movement, someone getting 10,000 steps per day will burn more calories than someone getting 1,000 steps per day.