Energy Expenditure During Exercise
Calories are the form of energy your body uses to function. Each day, your body “burns”, or uses, a certain number of calories irrespective of your physical activity – this is called your Basal Metabolic Rate (BMR). Your BMR is the amount of energy per unit of time that your body needs to operate at rest, fueling the processes of breathing, blood circulation, cell growth, maintaining appropriate body temperature, and functions of the nervous system. In total, your BMR accounts for 60 - 80% of the total energy your body expends in a day.
Interestingly, your body also requires energy to digest, absorb and store nutrients. Yes, your body actually uses calories in order to eat food! This is called the Thermic Effect of Food, and it accounts for about 10% of the total energy expenditure of your body.
What remains is the amount of energy required for daily physical activities. Activity energy expenditure is estimated to account for 15 - 30% of your total daily energy expenditure. Of course, the amount of energy expended for physical activity varies greatly depending on a person’s activity levels. Physical activity ranges from putting away groceries, to a leisurely walk, to a 5 mile run.
Given that activity energy expenditure is within an individual’s control, many people become curious to know just how many calories they are burning during their activities.
Energy Expenditure
As you may guess, many individuals overestimate their energy expenditure during exercise, believing they can compensate for poor dietary habits by increasing their physical activity levels. The saying “you can’t outrun a bad diet” is true. And forcing yourself to exercise in an effort to “earn” the foods you want to eat leads to an unhealthy mindset around eating, exercise, and health in general.
However, it is also very common for athletes to underestimate their required energy expenditure. Chronic underconsumption of calories for an athlete can ultimately result in RED-S, or Relative Energy Deficiency in Sport. This sub-optimal caloric intake can place athletes at risk for injury and illness, among other health concerns.
So, here I’m going to break-down the average energy expenditure of walking and running a mile. It’s important to note that these are estimates, and many variables can influence these estimates, including terrain, sex, and age, to name a few.
Walking One Mile
On average, you will expend 0.5 - 0.6 calories per pound of body weight per mile walking. For example, if you are a 150-pound individual, your body will use about 75 - 90 calories to walk one mile.
Running One Mile
On average, you will expend 0.7 - 0.8 calories per pound of body weight per mile running. For example, if you are a 150-pound individual, your body will use 105 - 120 calories to run one mile.
One of the reasons why running expends more energy than walking is that running requires your leg muscles to propel both feet off of the ground at the same time, whereas walking allows one foot to always remain grounded.
Knowing these metrics can help you understand the energy demands of two of the most common forms of physical activity. However, counting calories on a daily basis is generally not necessary. Instead, learning to respond appropriately to your body’s hunger cues is often the best way to accommodate your body’s energy demands. Typically, our bodies do a better job at regulating our energy needs than what we can estimate on paper, allowing us to simply enjoy a variety of balanced meals without the stress of tracking every calorie.
Working with a dietitian is a great way to better understand your individual energy needs and how to listen to your hunger cues! If you would like to work with me, schedule a FREE Discovery Call here to see if we are a good fit working together.