What Is Metabolism?
Metabolism is the word used to describe the chemical and physical processes in the body that provide energy for the maintenance of life.
Energy is neither created nor destroyed; rather, there is a transfer. You can think of your body as a bank, an efficient investment system. Many transactions are made each day.
The Role of Food in Your Body Bank
Food is the initial investment you bring to your bank. It provides a continuous supply of energy for the body cells, but it is not used directly. Digestion breaks down the carbohydrates, fats, and proteins into the simple forms of glucose, fatty acids, and amino acids, and these are deposited into different “accounts” in your body “bank.”
Some glucose is processed and used quickly for energy — like paying cash for a purchase. The remaining glucose becomes glycogen and is stored in the muscles and liver, similar to a checking account you can access when needed. Fatty acids, by contrast, are long-term investments — more like a savings account.
Protein: Building Blocks, Not Fuel
Protein provides amino acid building blocks for growth or repair of body tissues and to synthesize enzymes and hormones. It is used as an energy source only during periods of starvation, at the expense of other vital functions.
ATP: The Body’s Currency for Energy
When your body cashes in some of the saved glycogen or fatty acids, they release energy to form a compound abbreviated as ATP — your body’s “currency” to pay for movement. All biological work requires ATP to be broken down. This can happen through two pathways: anaerobic and aerobic metabolism.
Anaerobic vs. Aerobic Energy Systems
Aerobic production of ATP fuels sustained, lower-intensity activity. Your body slowly burns through glycogen or fatty acids — much like spending a savings bond gradually. Despite the negative view of fat, the body sees it as the gold standard for stored energy.
Carbohydrates provide 4 calories per gram and are stored as glycogen — enough for a 10-mile run or 1200 calories. Fat yields 9 calories per gram and is stored in nearly unlimited amounts. For instance, a 120 lb woman with 25% body fat has enough energy stored to run 1000 miles!
Metabolism in Exercise: The Body Bank in Action
The “body bank” analogy helps simplify how energy systems operate during physical activity. Anaerobic and aerobic systems often work together or alternate, depending on the intensity and duration of the exercise.
Understanding this can help you choose better workouts, whether you’re interested in training for performance or looking to manage weight through smarter energy investment.
Metabolism, Fat Loss & Fitness Motivation
People who enjoy exercise often appreciate how effectively their metabolism supports physical activity. If your goal is to shed excess fat and boost energy efficiency — it’s time to go on a metabolic “spending spree!”
For more science-based tips, visit our articles on improving flexibility or explore how weight gainers may not support long-term metabolic goals.