Pelvic Prime's Anatomy Academy Series: Weight Management
Metabolism
Metabolism is the process by which your body converts food into energy. For anyone looking to manage their weight, understanding how metabolism works is the first step. It is influenced by multiple factors, including age, hormones, muscle mass, and lifestyle habits. Insulin plays a critical role in regulating metabolism by controlling how your body stores and utilizes energy. Understanding how these systems interact can help you optimize your metabolic health and improve weight management outcomes.
Metabolism: The Engine of Life
How Your Body Uses Energy
Metabolism is everything your body does to keep you alive and functioning. It’s how your body creates, uses, and stores energy from food. This ongoing process is called homeostasis—keeping your body in balance.
Where Does Energy Come From?
Food is fuel: Your body gets energy from food, measured in kilojoules (kJ) or calories.
Energy balance matters:Too much energy? Your body stores it as fat.
Use more energy? Your body burns it to power your cells and movement.
Homeostasis: Just like your body regulates temperature, a thermostat keeps a room at a set temperature by turning the heater or air conditioner on and off.
Similar to how a fire burns wood for heat, your body converts food into usable energy.
Two Sides of Metabolism: Catabolism & Anabolism
Metabolism has two key jobs that keep you strong, healthy, and energized:
Catabolism: Breaking Down for Energy
Your body breaks down food (carbs, proteins, fats) into smaller building blocks. This releases energy to power your muscles, brain, and organs.
Think of it like fueling a fire—your body takes food and turns it into energy.
Your body uses energy to build muscle, repair tissues, and support growth. This is how your body heals injuries, builds muscle after exercise, and keeps your cells healthy. Any extra nutrients not used for building get stored as fat for later use.
Think of it like constructing a building—your body takes raw materials (nutrients) and uses energy to build and repair its structure. Just like a builder needs bricks, wood, and cement to construct walls and repair damage, your body needs proteins, fats, and carbohydrates to build muscle, heal injuries, and grow new cells.
Like constructing a building, your body uses nutrients and energy to repair, grow, and maintain structure.
🔎 Check Your Knowledge!
Which of the following best describes the difference between catabolism and anabolism?
A) Catabolism builds muscle, while anabolism breaks it down.
B) Catabolism releases energy by breaking down food, while anabolism uses energy to build and repair the body.
C) Catabolism and anabolism both store excess nutrients as fat.
D) Anabolism and catabolism are two names for the same process.
B) Catabolism releases energy by breaking down food, while anabolism uses energy to build and repair the body.
A simple way to remember it:
Catabolism = Breaking down for energy 🔥
Anabolism = Building up & repairing 🏗️
Metabolic Rate: How Your Body Engine Burns Energy
Now that you have a better understanding of what metabolism is, we can dive into how to make your weight management engine run more efficiently.
The Metabolism Engine Has Three Main Chambers:
Engine Chamber # 1: Basal Metabolic Rate (BMR). The BMR chamber burns 50-80% of your daily energy. This is the baseline energy needed for important bodily functions at rest such as:
breathing
circulation
cell repair
hormone regulation
The main factor influencing BMR is lean muscle mass, as individuals with more muscle require more energy to maintain their body’s functions.
The more muscle you have, the more energy you burn!
Men BMR = about 7,100 kJ per day, which is about 1,700 calories.
Women BMR = about 5,900 kJ per day, which is about 1,400 calories.
In simpler terms, if you were to lie in bed all day doing nothing, your body would still need around 1,700 calories (for men) or 1,400 calories (for women) just to keep your heart beating, lungs breathing, and cells working. Your body automatically burns this amount daily, even if you’re not exercising or moving much. The difference between men and women is largely due to muscle mass—since men typically have more muscle, their bodies require more energy to maintain it.
TEoF accounts for 5-10% of the energy you burn daily. This is the energy required to digest, absorb, and store the food you eat into the three Macronutrients:
Fats
Carbohydrates
Protein.
These macronutrients have different effects on your metabolism.
Fats have the lowest impact on metabolism (0-5%)
Carbohydrates cause a moderate rise in metabolism (5-10%)
Proteins have the highest impact on metabolism (20-30%), meaning the body burns more energy processing protein compared to fats or carbohydrates.
Yes & no.
Since protein has the highest Thermic Effect of Food (TEF)—burning 20-30% of its calories during digestion—your body uses more energy to break it down compared to fats (0-5%) or carbohydrates (5-10%).
This means that if you eat 100 calories of protein, your body may use 20-30 calories just to digest and process it, leaving you with a lower net calorie intake than if you consumed the same amount of calories from carbs or fats.
However, this doesn’t mean eating unlimited protein leads to endless fat burning. While protein can slightly boost metabolism, help preserve muscle mass, and keep you feeling full longer, overall energy balance (calories in vs. calories out) still matters most for weight loss or maintenance. But eating protein can support a higher metabolic rate and make it easier to manage body composition.
Think of Your Body Like a Car Engine:
Fats are like a hybrid car running on eco-mode 🚗. - Slow-burning and highly efficient, providing steady energy for long trips without needing frequent refueling. They are ideal for low-intensity activities and endurance.
Carbohydrates are like a gasoline-powered engine 🚙.- designed for quick acceleration when you need to get moving fast. They provide fast and easily accessible energy, making them the body’s preferred fuel for moderate to high-intensity activities.
Proteins are like a repair crew working on your engine 🔧. - they don’t provide immediate fuel but are essential for maintenance, muscle repair, and keeping your engine running efficiently over time.
So while protein has the highest thermic effect (burns the most calories during digestion), it isn’t the body’s primary fuel source. Instead, it plays a crucial role in supporting muscle mass, recovery, and metabolism stability—which helps your body run more efficiently in the long term.
This also explains why long-term high-protein diets, like Atkins or carnivore, aren’t always sustainable.
You wouldn’t expect your car mechanic to push your car around instead of using fuel—just like you can’t rely solely on protein to power your body efficiently.
A balanced diet with the right mix of fats, carbs, and protein ensures your metabolism runs smoothly and effectively.
Engine Chamber #3: Physical Activity Energy Expenditure (PAEE)
PAEE accounts for approximately 20% of daily energy use in active individuals and includes both planned exercise and incidental movement, such as walking, fidgeting, or daily tasks. Engaging in physical activity not only burns calories but can also increase your metabolism over time by preserving or building lean muscle. Since muscle tissue requires more energy to maintain than fat, staying active helps support a higher metabolic rate even at rest.
🔎 Check Your Knowledge!
Which of the following best describes the three main components of metabolism?
A) Basal Metabolic Rate (BMR) is the energy burned through movement, the Thermic Effect of Food (TEF) is energy stored from food, and Physical Activity Energy Expenditure (PAEE) is energy used at rest.
B) BMR is the energy required for basic bodily functions at rest, TEF is the energy burned during digestion, and PAEE is the energy burned through movement and exercise.
C) BMR accounts for the smallest portion of daily energy use, while TEF and PAEE contribute the most.
D) TEF is the body’s primary energy source, with fats providing the most immediate fuel.
B) BMR is the energy required for basic bodily functions at rest, TEF is the energy burned during digestion, and PAEE is the energy burned through movement and exercise.
This is correct because:
Basal Metabolic Rate (BMR) accounts for 50-80% of daily energy use and includes essential functions like breathing, circulation, and cell repair.
Thermic Effect of Food (TEF) accounts for 5-10% of energy burned and refers to the calories used to digest, absorb, and process food.
Physical Activity Energy Expenditure (PAEE) makes up about 20% of energy use in active individuals and includes both planned exercise and daily movement.
