Activity Factors

About The Activity Factor

There are lots of forumlas that give you your Basal Metabolic Rate (BMR) – Harris-Benedict, Mifflin-St Jeor, Katch_McArdle but knowing your BMR isn’t very useful because unless you are in a full body cast, you don’t rest all day.  “Activity Factor” is an attempt to quantify how active you are to determine a multiplier which will give you your total daily energy expenditure (TDEE). TDEE is a much  more useful number!

Basal Metabolic Rate (BMR) * Activity Factor = Total Daily Energy Expenditure (TDEE)

These activity factors were determined by research published in 1919 by Harris and Benedict, so they are a bit rusty but to date there is nothing better.    You might have had questions about what “Activity Level” to set, you are not alone. The problem is that these activity factors are very fuzzy and difficult to apply because they were based upon research back in 1919 and back then they didnt really do the kinds of exercise we do today.  Here is a chart that shows my interpretation of the activity levels and an alternative description to help you choose the proper level:

Multiplier   My Description Alternative Description
1.2 Desk job with little exercise Little to no exercise
1.375 1-3 hrs/wk of light exercise Light exercise (1–3 days per week)
1.55 3-5 hrs/wk of moderate exercise Moderate exercise (3–5 days per week)
1.725 5-6 hrs/wk of strenuous exercise Heavy exercise (6–7 days per week)
1.9 7-21 hrs/wk of strenuous exercise/work Very heavy exercise (twice per day, extra heavy workouts)