How Does the Body Use Calories?
Calories are a way to measure energy from the foods we eat and drink. Our bodies rely on calories to function, just like a lamp relies on electricity to work! We often see calories labelled on food packaging and menus. This value gives us an idea of how much ‘fuel’ we get from those particular food items.
A common myth is that exercise is the main way we burn calories. But in reality, our bodies are using energy all the time - even when we are resting! Understanding how our bodies use calories can help us make informed nutrition, movement, and overall health choices.
The 4 Ways Our Bodies Burn Calories
1. Basal Metabolic Rate (BMR) – About 70% of daily calorie use
BMR is the energy your body needs to keep you alive and represents the energy your body needs at rest! This energy is for important functions like:
- Keeping your heart beating
- Breathing
- Circulating blood
- Regulating body temperature
- Supporting brain function
- Repairing cells and tissues
Even if you stayed in bed all day, your body would still use most of its energy for these functions.
2. Non-Exercise Activity Thermogenesis (NEAT) – About 15% of daily calorie use
NEAT refers to the energy you use for anything that is not intentional, structured exercise, sleeping or eating.
This includes:
- Walking around your home or workplace
- Fidgeting
- Standing instead of sitting
- Household chores like cooking or cleaning
3. Thermic Effect of Food (TEF) – About 10% of daily calorie use
Your body needs energy to digest and process food. This is called the thermic effect of food (TEF) and accounts for about 10% of your daily calorie use.
Different foods have varying thermic effects. Whole, unprocessed foods require more effort to digest and metabolize than highly processed ones, meaning we burn more calories eating whole foods! For example, eating a whole apple means your body has to work to break down the fibre and natural sugars while drinking apple juice requires less effort—the sugar is quickly absorbed, and you burn fewer calories processing it. The macronutrient content of food also makes a difference, protein has the highest thermic effect, needing the most energy to break down, then carbohydrates, while fat requires the least amount of energy to break down.
4. Intentional Exercise – About 5% of daily calorie use
Exercise has a huge impact on our health, however when it comes to “burning calories”, it accounts for the smallest portion of daily energy use—about 5% for most people. This includes activities like:
- Running, cycling, or swimming
- Strength training
- Yoga or Pilates
- Group fitness classes
It may be surprising that intentional exercise has a relatively small effect on calorie usage and weight loss. Don't forget it plays a major role in improving health by reducing the risk of heart disease, certain cancers, diabetes, building muscle, helping with mental health, and more!
If you have questions or want to learn more about the ways the body uses calories, please let your Constant Health dietitian know!