What's the deal with BRM?
Saturday, May 04, 2013
BRM is a common enough term for those of us who are struggling with our weight, but how accurate can this "basal metabolic rate" formula be?
I tried five separate online BRM calculators, just for pure curiosity. Though two of the five did allow for activity levels to be set, the majority (as well as the one's I manually set) are at the base level, or no activity. The results are astonishing. From one I was told that I need to eat as little as 1371 calories a day to sustain basic body functions. Another claimed 1830 calories are needed. That is a whooping 459 calories in difference. Thats a freaking meal!!!!
So when we are taught that we need to eat about 500 calories less than our BRM to lose around a pound a week (without exercising), it makes me wonder what forumla should we follow. Should we follow our highest estimated BRM and eat 1330 calories a day, or follow the lowest one and eat 871 calories a day? Both are extremely low for anyone active (and the 871 are low for anyone besides that of a toddler).
So, here I start thinking about my heart rate monitor (HRM for short). It is claimed to be fairly actuate when the information is all up to date (weight and resting heart rate). So I burn anywhere from 450 (Friday's run was a little weird since I tried to help a lost dog that just wanted to bite me) to 700 calories in a running workout. This doesn't include the strength training I do afterwards. So I am also already eating around 1500 calories a day. So factoring an average 500 calories burned from working out, my average BRM (1601.4), my average intake of food is 1,600 calories, it means I am burning 501.4 calories a day.
This tells me I should be losing weight. But don't we also learn that muscle burns more calories than fat? That why someone with a higher body fat percentage burns less calories working out at the same intensity as someone with a lower body fat percentage. That is why it is encouraged to do both cardio and strength training. So why doesn't any of these BRM's factor in fat or muscle percentages? What about metabalic disorders, or thyroid issues...do those change the BRM? Should I really take into consideration how many calories to eat based on some BRM that could be over 500 calories wrong?
I don't know. But what I do know, is something doesn't add up here. And that something might be why the scale is refusing to move. I wish I had more answers, but every time I have an answer, it makes me question it further.
Losing weight might be as simple burning more calories than you eat. But how many calories should you eat?
Below is the five websites I used to calculate my BRM and the number they came out with. I used the same values (age 26, height 5 foot 1 inch or 61 inches, female, 153 pounds, and when applicable sedentary life style since some were automatically that).
myfitnesspal.com = 1371 calories
bmi-calculator.net = 1485.05 calories
bmrcalculator.org = 1539 calories
muslceandstrength.com = 1782 calories
safedietplansforwomen.com = 1830 calories
Member Comments About This Blog Post
I wonder about his too, sometimes. Don't forget Spark has it's own calculators! The general consensus I've read from other people's blogs is that Spark calorie numbers always seem a little high... unless you are doing everything right and not seeing any scale movement. Then, it's time to increase calories a little bit.
I, personally, always look at the low end of things. I usually use BMI-calculator.net. Out of the ones you listed, it is one of the ones with the lower calorie requirement. Even though I exercise 6 days a week, I still look at the "low active" numbers, since I am only exercising for 45 min or so a day, and the rest of my day is pretty sedentary. What gets me is how difficult it is to estimate activity level, and I think that's where the numbers start to go funny.
I've also used this site in the past:
That one is kind of interesting, because it shows a daily decrease of calories until you reach goal. I think that one is handy if you are trying to reach a goal within a set time period, because it will tell you what you need to do to get there in the time desired. Also, I use it to tell me when I need to up my exercise. Anytime something tells you to eat under 1200, I don't do it, because anything less without direct doctor supervision is very unhealthy. (And even then, most docs probably wouldn't recommend it)
If that site I just linked ever tells me that I'd need to dip below 1200 cal/day to reach my goal by X date, I know that it is unrealistic for me to be able to hit that target, and I need to either scale up my exercise or move the date back.
Unfortunately, that bring me back to being stuck on what constitutes light activity vs. moderate activity! ARGH! I mean, I feel like I'm working pretty hard, but it's just a small slice of time out of the day, you know? lol
Anyway, you're totally right. None of those sites can take into account medical issues that would effect the metabolism, just like BMI can't tell if you are athletically built or not! It's really frustrating when you want more detailed info and our current science only gives us vagaries :(
My policy? When in doubt, bump protein and lower carbs! HAH!
1683 days ago
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