Metabolism 101: How it Works
In brief
How does metabolism actually work?
Metabolism is the sum of chemical processes that convert food into energy, split into three components: basal metabolic rate, which accounts for 60 to 75 percent of daily energy use just to keep the body functioning at rest, the thermic effect of food, which uses about 10 percent to digest and process nutrients, and physical activity, which accounts for 15 to 30 percent. Factors like age, muscle mass, body size, hormones and genetics all influence metabolic rate, with metabolism typically slowing two to three percent per decade after age twenty.
Understanding your metabolism is the first step to making informed decisions about your diet and fitness. Let's break down the science in simple terms.
What is Metabolism?
Metabolism refers to all the chemical processes in your body that convert food into energy. It's not just about burning calories, it's about how your body uses energy for everything from thinking to breathing to moving.
Components of Total Daily Energy Expenditure (TDEE)
Basal Metabolic Rate (BMR)
60-75%Calories burned at rest to maintain vital functions like breathing and circulation.
Thermic Effect of Food (TEF)
10%Energy used to digest, absorb, and process nutrients from food.
Physical Activity
15-30%Calories burned through exercise and daily movement (NEAT).
Factors That Affect Your Metabolic Rate
- Age: Metabolism typically slows 2-3% per decade after age 20
- Muscle Mass: More muscle = higher resting metabolic rate
- Body Size: Larger bodies require more energy
- Hormones: Thyroid hormones significantly impact metabolism
- Genetics: Some variation in metabolic efficiency is inherited
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