BMR Calculators and the Activity Factor for Weight Loss
Jonathan brought up a good question yesterday about BMR calculators and the activity factor that some BMR calculators add on.
Natures Lumber Jacks
BMR calculators are based on various known assumptions and measurements about your lean body mass and how many calories your lean body mass will burn. These calculators usually need your height and weight and sometimes your age and other things like your wrist or waist measurements.
You can get a decent estimate of your BMR if you used 3-4 calculators and take the average of these.
BUT, there is also an activity factor that some of them suggest. The problem with these activity factors is that they are based on very old research that used lumberjacks as their example for daily activity. Needless to say, a day of lumberjack work is a ton of activity and will burn way more calories than any workout you or I can do after work.
The point is the activity factor that these calculators use is not accurate or realistic to any workout you or I will probably be doing. In fact, assuming that you’re burning less calories in the gym than any calculator suggests is a good bet if weight loss is your goal.
Forget about activity factors and just assume that the total amount of calories you can burn in a day comes exclusively from your BMR. From there just assume any extra calories you burn in the gym will be a bonus.
When it comes to calorie burning and fat loss it will always serve you well to err on the side of less than more. In other words the following 3 assumptions will be the only way to use BMR calculators and food labels to your advantage:
1. Assume that your activity burns less calories than the cardio machines or calculators say
2. Assume your BMR is less than the calculators say
3. Assume that food labels are always underestimating the actual amount of calories in that food
Making these 3 assumptions will be the best way to keep you a step ahead in the calories in vs out game.
John
20 Responses to “BMR Calculators and the Activity Factor for Weight Loss”
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February 9th, 2010 at 8:15 am
Nice beaver!
February 9th, 2010 at 8:57 am
John, thanks for answering my question and helping me understand more about the activity factor. What you proposed is a good solution because it keeps one from overeating to compensate for “calories burned.” How many people do you know that overeat because they “worked out” and their body needs the extra fuel? I can see how the activity factor in these BMR calculators would lead some people to believe that they can eat 500-700 more calories than their BMR, which effectively sabotages their weight loss goals. Keep up the good work!
February 9th, 2010 at 12:26 pm
Right on, Jonathan. Absolutely. As a matter of fact, the extra calorie burn, according to these calculators, can actually be as much as 2000 calories above the estimated BMR! Yikes!
According to this calculator:
http://www.bmi-calculator.net/bmr-calculator/
my BMR is about 2322 calories. Sounds reasonable. But when you look at activity levels:
Sedentary: 2786
Lightly active: 3193
Moderately active: 3565
Very active: 3968
Extremely active: 4370
So the highest activity level is 2000 calories above BMR. Even “lightly active” is 800 calories more. Umm… probably not.
And of course, the other point is that there are plenty of manual laborers, athletes, etc., who are overweight, despite being very active. You can’t outrun a doughnut, as they say. Or two or three or four doughnuts, as the case may be. So, yeah, sticking with BMR, or going under a couple of hundred of calories, is a good idea. I could do much worse than simply assuming I burn about 2000 calories a day and try to go under that.
February 9th, 2010 at 2:18 pm
hey all,
just to back up what JB originally wrote and then what Jordan followed up with, i have been tracking my calorie balance fairly rigorously on fitday.com for months now and this has been very interesting in terms of zeroing in on my actual intake versus my actual burning (within fairly vague parameters, of course). i have also been using a Timex heart rate monitor during my workouts as well, which adds another dimension.
like Jordan wrote, fitday.com gives a number of options for activity level beyond resting. my current BMR is estimated at 1,921 calories and i am given the options of Sedentary, Seated All Day, Mostly Seated, Standing Work or Strenuous Work/Highly Active (the totals for each are also more or less what Jordan put down). after lots of trial and error, my current setting is Sedentary, which puts me at around 2,338 calories/day. then the fitday estimations for my workouts are at around 438 calories for each hour weight lifting workout and 180 calories for 15-20 minutes of interval training. this is in contrast to the 837 and 400-600 calories reported by my heart rate monitor.
using these settings, my actual weekly weight loss over the past month has been within .1 pounds of my estimated weight loss, so this seems to be pretty accurate overall. my lifestyle is NOT sedentary and according to my heart rate monitor, which should be the most accurate reading i can get, i am burning 2 to 3 times as many calories during exercise as i am logging on fitday.com, but if i were to use these results to gauge my calorie intake i would have at best just broken even instead of losing around 2.5 lbs. a week.
however, the reality is still that while overall my current estimations are relatively accurate, specifically my BMR could be higher and/or i could be burning even less calories through training, or some other combination, but generally speaking i think i have found my basic numbers for gauging calories in v. calories out. for me, though, by far the biggest point is that using the literal estimations like Very or even Moderately Active lifestyle for my BMR and the calories my heart rate monitor says i burn would lead me to grossly overestimate my calories burned, which in turn would actually probably have me gaining fat at this point, even though i would be able to easily justify my calorie intake using the best technology available to me. it would then be easy for me to construct some story about how my body is just different from others, and that i must just not be naturally able to lose weight, or some variant of that, which would then allow me to justify not getting in better shape, etc.
(for the record, though, at my current numbers, weight, level of training, etc., my BMR is around 1,900 calories/day and i appear to be burning around 2,750 calories/day. all of this is subject to change as there are any number of alternative explanations, but for now this seems to be pretty accurate)
February 9th, 2010 at 2:27 pm
Shea,
Great stuff. And I would just add that you’re probably overestimating the calories you are burning at exercise. And just to be clear, the amount of calories your estimating that you are burning during exercise must be subtracted from the amount of calories you would have burned during that hour even if you didn’t exercise.
In other words, your BMR is 1900 calories per day. That is 80 calories per hour. Lets say you do a workout for 1 hour that is estimated to burn 400 calories. Your net caloric deficit is actually 400 – 80 = 320 calories (because you were going to be burning the 80 calories anyway even if you just sat on the couch)
This last point is something everyone overlooks.
JB
February 9th, 2010 at 2:47 pm
Awesome post. Just to add to the point, since I happen to be logged into my calorie counting website, I’ll use myself an example.
Forget about the BMR calculator, right now (2:30pm) I have consumed roughly 950 calories so far today (usually lower but my secretary brought in carrot cake and I wasn’t about to not have a piece). I will probably have another 400 cals at supper. I play hockey tonight, which means I will probably have some beer after, and maybe a few chicken wings. Lets assume another 500 cals there. My estimated intake for today will be about 1850 – 2000.
According to the same website, based on my 1hr work-out this morning and my 1 hour hockey game, I will have burned 1149 calories!!! So apparently my net consumption for today will be around 850 calories!! Hell, I may as well have another piece of carrot cake and maybe a couple more beers!! (jk). I figure the hockey and the workout MAYBE erased the carrot cake, and possibly a chicken wing…..
You can see how it’ll get away from you quick if you place faith in these online estimators. Again, awesome post.
February 9th, 2010 at 3:33 pm
John, You and Brad Pilon are the big promoter of eating opposite than the bodybuilding industry suggest. I have just seen a nutrition plan of Adonis index
http://www.scribd.com/doc/2244809/The-Adonis-Effect-Build-a-Body-that-Women-Cant-keep-their-Hands-off
and it seems a strict and bodybuilding like eating plan for me. Avoid carbs, lot of protein, eating 6 or more times per day? So what about eating what u like and dont care about bb bs?
February 9th, 2010 at 3:53 pm
Wood,
We offered a structured competition style meal plan for anyone who wanted it. Even though I think it’s simplest to figure out what to eat on your own, some people still wanted a plan to follow. The plans we used were the best option I could find (although not something I would use personally). The point is that there is no specific way to eat, and we’re presenting all options. These plans are a structured example of what is possible, and things like ESE and what I do are the other end of the spectrum. We all fall somewhere in between. The only disadvantage to my style is that there is no plan to follow, I just eat whatever I like and count calories.
JB
February 9th, 2010 at 4:21 pm
Hey John, long time no speak.
This is a great post. I didn’t know this important detail about activity factors until Pilon informed of this quite some time ago.
Erik
February 9th, 2010 at 6:01 pm
thanks, john.
yeah, the fitday estimations of calories burned during exercise seem high to me as well, but that is the next step for me in this little experiment is to try and zero in more accurately on numbers like that.
overall, the 2750 calories/day burned minus 1500 calories/day consumed seems to account pretty well for my fat loss experience, but i am not very confident in the composition of the underlying factors. the one ‘known’ (to some extent) that i have is calories consumed, with the two unknowns of metabolic rate and calories burned during exercise. of these two, i assume that my BMR is closer to known so the one true-er unknown is that damn calories burned during exercise number.
anyway, for me what this all means is to focus on the one factor i more or less ‘know’ and can control, which is calories in, and just play around with the other stuff for fun. it’s tough to go wrong with maintaining a true calorie deficit to lose fat, irregardless of what else is going on. also, more than anything i just hope my experience helps other people to realize just how shaky and fluid these kinds of estimations are, and so to just focus on the one thing you can have some control over (which is what goes in your mouth), and the rest will more or less take care of itself.
February 9th, 2010 at 6:06 pm
(oh yeah, and one nice thing about the way fitday.com calculates calories burned is that it does subtract it out of the total the way you suggest, so it does at least have that going for it too.)
February 9th, 2010 at 6:20 pm
Hey john,
I listened to an old podcast of you and Brad Howard and you all were discussing that health cannot be easily defined and I agree with that. Anyway, I believe you said in the podcat you had tendonitis in your left tricep. I have been having some aggravation in my tricep as well after a small “bump” or swelling has occured where the bottom of the tricep connects to the elbow. Could this be simply from overworking or tendonitis, etc? I took some time off but the small bit of swelling never went away. I also can’t really say that it hurts that often but figured I would see if you had any experience with anything such as this.
thanks alot
Brandon
February 9th, 2010 at 8:17 pm
Brandon,
I never had a visible bump or one that I could feel like that. I would just go straight to the doctor if it’s not going away. Anytime I have anything like that I go straight to the sports medicine doctor I used to work with.
JB
February 14th, 2010 at 12:02 am
John,
Really enjoying your posts. My BMR is around 1400 cals, no activity taken into account. What do you say about the widely propounded theory that it is ‘dangerous’ for a woman to eat less than 1200 cals per day (which is what I would need to do on a traditional ‘diet’ to lose any more weight)?
FYI I am doing eat stop eat and feel like I have hit lifestyle pay dirt. I assume that if you fast once or twice a week, then there is no need to eat fewer than 1400 cals per day on the other day in order to keep losing (just not more)?
Cheers, Mel F
February 21st, 2010 at 10:13 am
So, what are the instructions for fat loss then? Eat AT your ‘assumed’ BMR and let whatever additional caloric burn create a deficit, or is it to eat below the BMR to create a deficit (plus the small amount you get via exercise)?
February 21st, 2010 at 6:12 pm
KP,
Your second suggestion is more practical (eating below BMR and a small amount of calorie burning added via exercise)
It’s much easier to eat 500 calories below BMR than it is to try and use exercise to burn 500 extra calories every day.
JB
March 13th, 2010 at 12:16 pm
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May 16th, 2010 at 7:53 pm
I disagree with above. I am a registered dietitian and the body of research I have seen suggests that the basal metabolic rate calculators are accurate within 10%. Thus the most conservative way to use the BMR numbers is to take 90% of estimated as fact.
In general, your BMR is the calories you consume per day is meant to satisfy your basic body functions for respiration, muscle repair, etc. More calories are required for the thermic effect of food (digestion, peristalsis). Still more are necessary for activity.
If you eat below your estimated BMR, you are not providing enough energy for your basic body needs and activity you do beyond this level diverts calories from your basic function toward activity. This is not appropriate unless you have a legitimate amount of EXCESS body fat to lose.
Activity factors are meant to account for the amount of activity you do plus exercise. I don’t know the research on the accuracy of activity factors. But, ignoring them completely is unlikely to produce a healthy weight loss.
I would recommend using the BMR at 90% of estimated, plus an appropriate activity factor and subtracting 250-500 cal/day of food intake. You will not get a super quick weight loss, but you will be less likely to feel hungry, be prone to binge eating or “cheating”, and use the minimum amount of muscle protein for energy.
Also, it’s most important that you are making relatively accurate assessments about the amount of food you eat since weight loss tends to be tripped up by inaccurate reporting of intake and underestimating the portion sizes and thus the calorie counts of food.
If you are following the above information, have a reasonable weight and normal amount of body fat, you might not lose weight but that might be your biological set point. It would take you longer and more effort to lose weight than someone who has actual excessive body fat to lose. This isn’t because you are doing something wrong, take it as a compliment from nature. Shift your focus to building muscle (which you should not restrict calories to do) and you might achieve the more toned look you want.
http://www.facebook.com/#!/pages/Jaimie-Winkler-dietitian/168637712434?ref=ts
May 31st, 2010 at 8:30 pm
Howdy there,Excellent blog dude! i am Tired of using RSS feeds and do you use twitter?so i can follow you there:D.
PS:Have you thought to be putting video to your web site to keep the people more entertained?I think it works.Best wishes, Nichole Krough