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03 September 2008 @ 05:20 am
"We get a lot of email about this"  
So it seems part of the reason that i was getting confusing answers for my BMR is that there are actually two different BMR formulas, and despite the fact that the newer and better one (MD Mifflin and ST St Jeor) was created "recently" in 1990, most sites that calculate it for you use the older formula (Harris and Benedict.) In order to resolve this "problem," apparently the new formula is referred to as the RMR or "Resting Metabolic Rate."

So according to the calculator on this site (which seems to be the most informative in regards to this issue that i've found so far) i had a BMR of 2042 and RMR of 1904 at 210 lbs, and at 200 lbs it's now a BMR of 1979 and RMR of 1858. The RMR figures match what i get plugging in the numbers for the equation from wikipedia, so that's good.

So if i use the 1.2 activity level ("Little or no exercise and desk job," which despite intermittent bouts of rollerblading and dancing describes me most of the time) then my adjusted BMR is 2375 and adjusted RMR is 2230.

However on the earlier information page it says "if you are looking for an estimate of how many calories you need or burn in a day, we suggest that you not use BMR or RMR at all. We suggest that you calculate the actual activities that you perform in a 24 hour period as described in Calculating Daily Calorie Needs."

Okay, i'm willing to try that, so i came up with the following theoretically average schedule and results from plugging it into their activity calculator as described:

Sleeping - 572 calories in 7 hr
Showering (self care) - 91 calories in 30 min
Dressing and Undressing - 91 calories in 30 min
Driving - light vehicle (e.g., car, pick-up) - 181 calories in 1 hr
Computer Work (typing) - 1,157 calories in 8 hr 30 min
Walking - 2.5 mph - 68 calories in 15 min
Eating - sitting - 68 calories in 30 min
Computer Work (typing) - 408 calories in 3 hr
TV - watching - 159 calories in 1 hr 45 min
Reading - reclining - 91 calories in 1 hr

Which all looks okay in theory, until it gets totaled up as:
Total: 2,886 calories in 24 hr

Um, wait, my sedentary 1.2 life style is supposed to be about 2230 based on my RMR, how does adding up the elements of such a lifestyle result in a theoretical 2886 calories?

In fact, let's test the most sedentary life possible outside of being independently wealthy, a telecommuting techie who does nothing but lie in bed reading the rest of the day.

Sleeping - 653 calories in 8 hr
Computer Work (typing) - 1,089 calories in 8 hr
Eating - sitting - 68 calories in 30 min
Reading - reclining - 680 calories in 7 hr 30 min

Totals: 2,490 calories in 24 hr

So even a bare minimum lifestyle is 260 calories over the sedentary 1.2 activity level. Clearly the math is kind of wonky somewhere.

They do have an entire page about the accuracy of the calculator which discusses a lot of issues, though not specifically why a minimum amount of activity results in a calories use higher than a 1.2 activity level.

However i was very amused by the following tidbit :)

"In addition, we believe that the METs assigned to a few of the activities are either too high or too low. We originally assumed that some activities had been assigned very low METs because they were based on a period of time that included periods of rest. For example, in Gymnastics a notable amount of time is spent resting and waiting ones turn to perform; in Surfing much time is spent waiting for a good wave. This could explain why these activities have been assigned the same MET as Bakery Work which is much less strenuous but is performed on a continuous basis.

Perhaps similar logic applies to Sexual Activity - Vigorous, which has the same MET as Sewing and Knitting. We get a lot of e-mail about this."

In any case, it's clear that the low end of my scale should probably be somewhere between 1858 and 1979 calories (so 1918 for today is right on! =) That's a negative calorie expenditure of somewhere between 372 and 1028 calories, depending on which set of math you want to believe.

And in a totally random coincidence, patrissimo just posted a link to an article claiming that occasional binges while dieting, in particular high carb binges, are good for you. This fits rather well with my philosophy that all things should be taken in moderation, including moderation :)
 
 
Current Mood: amusedamused
 
 
 
Catbirdcatbird on September 3rd, 2008 03:20 pm (UTC)
Thanks for posting this link!

I'm also tracking my food in hopes of loosing weight. On weekdays I'm fairly good about sticking to below 2000, which is about 400 short of what fitday says I should be using. So far I think I've lost 4 lb's this past month (darn Ikea scale is worth crap though, all 4 lbs were lost in 1 day :P, so might not be accurate). FitDay has been my friend and tool of choice in this.

Now if I only could motivate myself to get up off the couch and go for a bike ride. I miss my riding buddy in Boston :(
DonAithnendonaithnen on September 3rd, 2008 04:10 pm (UTC)
It's too bad we're not a little bit closer, we could go rollerblading/biking together :)

If my scale is right then i've lost about 8 lbs in the past three weeks, but now i've been stuck at 199.something for the past three or four days =P

So does fitday have any way of calculating your daily calorie count without signing up for their program and/or downloading the software?
Catbirdcatbird on September 3rd, 2008 04:55 pm (UTC)
fitday does have a way of calculating your daily calorie count (both intake and demand) but to use it you need to sign up for a free account (so far no spam from them). They also calculate your nutritional intake so you can notice that you are only getting half your recommended allotment of iron or something like that.
shelleycatshelleycat on September 3rd, 2008 04:25 pm (UTC)
Hey! My tagline used to be moderation in all things, including moderation. :)

The calculator says my RMR is 1,366 and BMR is 1502. Sounds about right. Except I usually only eat 1,000 calories!
DonAithnendonaithnen on September 3rd, 2008 07:59 pm (UTC)
Thank the gods i'm not you! I would starve if i had to eat that little every day! ...er, so to speak :)

And wait, if you're consistently eating over 300 calories less than your RMR than how are you even still mobile?!? =P Go eat something! :)
shelleycatshelleycat on September 3rd, 2008 08:49 pm (UTC)
I guess the few days each week that I try to make up for not eating more than make up for it. Two pieces of cake and two protein bars is an entire day's worth right there.
Kirinkirinn on September 5th, 2008 04:02 pm (UTC)
Here's something odd/interesting: Unlike both you (higher) and shelleycat (lower, but also female which I'm sure changes the equations plenty), my BMR and RMR are basically the same (just 5 calories different).

Of course I have no idea what my daily calorie intake is, but since my weight's been more or less stable for like 15 years I presume it's in the right ballpark. What I really need to be in better shape is more exercise. :P