Determining your Energy Needs

July 4, 2018

Determining your Basal Metabolic Rate
To determine your calorie level it is helpful to start with your Basal Metabolic Rate (BMR) also know as Resting Energy Expenditure (REE) or Resting Metabolic Rate (RMR). This is the amount of energy needed to sustain basic physiological function and no more. In other words, this is the amount of energy you would need if you were to lay in bed all day and not move. To calculate this you will need your current body weight, height, and age. There are two equations that are used most often to calculate this number, the Harris Benedict Equation and the Mifflin St. Jeor Equation. Both are provided here and it is recommended to use both and calculate the average between the two. If you want to be as accurate as possible you could do a resting energy metabolic test in which you can go into a lab or clinic and they will measure your resting metabolic rate using your breath and resting heart rate.

Harris Benedict Equation:
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in years )

Mifflin St. Jeor:
Women: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161
Men: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5

To determine your weight in kilograms divide your current body weight by 2.2. 
To determine your hight in centimeters take your height in inches and multiply by 2.54

Most women will have a BMR around 1,100-1,500 calories and men will be on average around 1,400-1,800 calories. If you get a number that is not close to these numbers you may want to recheck your math. 

Determining Daily Calorie Requirements: 
Not that you have your RMR or BMR calculated, you will want to calculate how much energy you will need to maintain your weight. This will depend on activity level and this may fluctuate slightly day to day. You will want to use your resting metabolic rate and multiply this number by an activity factor. You can adjust and have a range or different

 

calorie goals depending on how active you are. Here are the activity factors:
1.1- 1.2 = sedentary or little activity (no exercise) and work a desk job
1.4 = light activity (exercise 30 minutes or less 3 days per week and have a desk job)
1.55 = Moderately active (moderate activity 30-60 minutes 5 days per week and work mostly at a desk job or you have an active but don't exercise on a regular basis)
1.7-1.8 = You are very active (hard sports around 60 minutes or moderate to high intensity 6 days per week around  but otherwise mostly a desk job or active at work and exercise moderately)
1.9-2 = Very active and have an active job
2-2.5 = training for a marathon to ironman distance race (more than 10 hours per week), very active 

Once you have determined your energy needs you may want to use that number to maintain your weight. If you goal is weight loss it is recommended to consume about 500 calories less per day to lose one pound per week. It is a little more complicated than calories in vs calories out, but this can be a starting point. If you want to gain weight it is recommended that you increase calories by 200-300 per day. This will provide a slow (and hopefully mostly muscle) gain of about 1/2 pound per week. 
 

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