Your PowerFuel™ Energy Budget

© Elizabeth (Beth) Mansfield, PhD, Peak Performance, Ottawa, ON

Last month, we introduced the concept of “power fueling” your body with an individualized energy budget. This ensures that you get enough energy into your body to fuel your training and racing efforts. This month, we’re going to look at how to calculate that energy budget.

The energy you need for life and sport comes from the foods and beverages you eat. What you don’t use right away gets turned into body fat or put into storage in your muscles. The bonus of your run training program is that it increases the capacity of your muscle cells to store the energy from the foods you eat. Skeletal muscles store energy in the form of carbohydrate and fat and then use this energy during high intensity and endurance activities. Energy is also stored as body fat, which becomes an important energy source during long, slow distance training (and for those times when you go too long without eating).

Your specific energy needs will depend on a bunch of different factors: your body size, genetics, gender, and physical demands of your daily lifestyle and training program. Your level of fitness also acts to moderate these requirements; the fitter you get, the less energy you need to support your usual physical activities. That also means that as you get fitter, you may need to take more control of your fork—unless you are also upping the training intensity and volume.

Despite all these factors, the following three-step process has been shown to be very accurate in determining how much energy in calories you need to fuel your body to meet your lifestyle and training needs.

The three steps are:

  1. Determine your Resting Metabolic Rate
  2. Determine your daily physical activity level.
  3. Calculate your daily energy needs.

Step 1: Determine your Resting Metabolic Rate (RMR).
Your RMR is the amount of calories you need simply to sustain life in your body. Your RMR does not factor in any movement or other physiological processes that require more energy (e.g. eating food, digesting food, going to the bathroom, walking your dog…you get the gist…)!

For an individual resting metabolic rate evaluation, the use of indirect calorimetry is recommended. In conditions where this technique cannot be used, there are equations that can predict the RMR of athletes and non-athletes.

One of the best equations for athletes (+/- 220 Calories) is the following. You’ll need your weight in kilograms and height in centimetres.

RMR (kcal/d) = – 857 + 9.0 x (Wt in kg) + 11.7 x (Ht in cm) 

So, if you are 75 kg and 174 cm tall, your RMR is 1865.5 ±220 kcal/day

Step 2: Determine your daily physical activity level.

Now use the following chart to determine your daily physical activity level.

Activity Levels

If you’re a recreational runner training for a marathon and you’re doing 5 workouts a week ranging between 1 hour and 3 hours, we’ll say that is Very Active.

Step 3: Calculate your energy needs for different activity levels

Finally, using the chart below, multiply your RMR by your activity factor from step 2 to get your daily energy needs.

Daily Energy Needs Calculation

Once you know your daily energy needs, you can start translating this into foods. Check back next month to plan your PowerFuel™ nutrition plan to meet your daily energy needs!

About Beth Mansfield
Dr. Elizabeth (Beth) Mansfield, PhD, RD is a Registered Dietitian, Sport Nutrition Specialist, and Certified Exercise Physiologist with Peak Performance in Ottawa. Beth educates Canadian athletes on sport nutrition for health and performance.

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