Is the TDEE equation wrong?
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skinnylion
Posts: 213
Hey guys,
I was just fooling around with my fitness spreadsheet and noticed something kind of interesting! I started using my Fitbit again at the beginning of this month because I hadn't been losing weight over the summer. My estimated TDEE w/ 9,000 steps per day, (which is a good amount of walking on campus) totals 2,100 calories.
Comparing that to the equation that's supposed to give TDEE, I classify as "Sedentary." All this time I felt like I was at least doing a "Lightly Active" amount of exercise - so, trying to cut at that amount of calories, I think I was actually just eating my TDEE. No wonder I haven't been losing!
And if any of you are interested in checking my math:
Height = 65 inches
Weight = 171.6
Age = 20
Gender = Female
Harris-Benedict BMR
= 655+((9.6*(171.6/2.2))+(1.8*165.1)-(4.7*20)) = 1607 calories
Base Energy Expenditure (also Sedentary TDEE)
= (1607*1.2)+(1607*0.1) = 2089 calories
Using the Lightly Active coefficient (1.375) in the calculation, I get a value of 2455 calories expended in a day. According to my Fitbit, the only time I came even relatively close to that number with normal day-to-day stuff was when I was on my feet 8 hours at work. Just thought I should bring this up for any of you that might be interested.
I was just fooling around with my fitness spreadsheet and noticed something kind of interesting! I started using my Fitbit again at the beginning of this month because I hadn't been losing weight over the summer. My estimated TDEE w/ 9,000 steps per day, (which is a good amount of walking on campus) totals 2,100 calories.
Comparing that to the equation that's supposed to give TDEE, I classify as "Sedentary." All this time I felt like I was at least doing a "Lightly Active" amount of exercise - so, trying to cut at that amount of calories, I think I was actually just eating my TDEE. No wonder I haven't been losing!
And if any of you are interested in checking my math:
Height = 65 inches
Weight = 171.6
Age = 20
Gender = Female
Harris-Benedict BMR
= 655+((9.6*(171.6/2.2))+(1.8*165.1)-(4.7*20)) = 1607 calories
Base Energy Expenditure (also Sedentary TDEE)
= (1607*1.2)+(1607*0.1) = 2089 calories
Using the Lightly Active coefficient (1.375) in the calculation, I get a value of 2455 calories expended in a day. According to my Fitbit, the only time I came even relatively close to that number with normal day-to-day stuff was when I was on my feet 8 hours at work. Just thought I should bring this up for any of you that might be interested.
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I was just fooling around with my fitness spreadsheet and noticed something kind of interesting! I started using my Fitbit again at the beginning of this month because I hadn't been losing weight over the summer. My estimated TDEE w/ 9,000 steps per day, (which is a good amount of walking on campus) totals 2,100 calories.
Comparing that to the equation that's supposed to give TDEE, I classify as "Sedentary." All this time I felt like I was at least doing a "Lightly Active" amount of exercise - so, trying to cut at that amount of calories, I think I was actually just eating my TDEE. No wonder I haven't been losing!
And if any of you are interested in checking my math:
Height = 65 inches
Weight = 171.6
Age = 20
Gender = Female
Harris-Benedict BMR
= 655+((9.6*(171.6/2.2))+(1.8*165.1)-(4.7*20)) = 1607 calories
Base Energy Expenditure (also Sedentary TDEE)
= (1607*1.2)+(1607*0.1) = 2089 calories
Using the Lightly Active coefficient (1.375) in the calculation, I get a value of 2455 calories expended in a day. According to my Fitbit, the only time I came even relatively close to that number with normal day-to-day stuff was when I was on my feet 8 hours at work. Just thought I should bring this up for any of you that might be interested.
Due to rounding errors in difference, I get 1611 BMR, so close enough.
Now, the more accurate Mifflin which MFP also uses is 1549, so still 60 less, not that bad.
But, both studies for those equations was on participants already at healthy weight, which means unless you have maintained the same ratio of fat to fat-free mass, it is inflated also.
That's why it's usually recommended to get your estimated bodyfat % down, because that Katch BMR equation is much more accurate. And while it underestimates for overweight folks, not nearly as much as the others inflate.
So your FitBit for walking and other daily activities has the best chance of accuracy. Though, it is basing your foundation of calorie burn on the least accurate Harris BMR estimate. That can be tweaked once you know your bodyfat% by changing your height on the FitBit site.
Anyway, if your deficit took you down to eating around 2100 daily, that would indeed be a reason for no weight loss.
Try this spreadsheet linked in this post to input your FitBit stuff into, get better TDEE avg, and see what deficit would be for you.
http://www.myfitnesspal.com/topics/show/717858-spreadsheet-bmr-tdee-and-deficit-calcs-macros-hrm
And indeed, not only is the Harris BMR calc the oldest and least accurate now, the Harris TDEE levels and values is from a study from 1919, so not exactly up to date either.
That spreadsheet has a newer one available as first option - though for you the FitBit is better.0
