differences in BMR estimates

slemonfit
slemonfit Posts: 97 Member
edited February 20 in Health and Weight Loss
i tried estimating my basic metabolic rate at a few websites but they give different results

i'm 5'1 and now i weigh 150 pounds, but i dont have any muscle and 40 pounds of that is from fat
i have light bones, i used to weight about 110-120 pounds about 7 years ago but i got lazy and gradually gained like 5 pounds each year that now i want to lose, and when i was at that weight i looked normal, i never really had any muscle and my bones are thin for example i can wrap my fingers around my wrist and my hands are already very small

on one counter,
if i enter my weight as 150 pounds, it says that my bmr is 1461, and i need 1754 calories a day
for someone 120 pounds, it says the bmr is 1331 and they need 1598 calories a day
for someone 110 pounds, it says the bmr is 1288 and they need 1546 calories a day

is the difference assuming that a 150 pound person would have also more muscle than someone 110 pounds? because i know my weight gain is only fat and no muscle, so should i enter my weight of 150 pounds still? does someone burn 200 more calories/day just because it takes more energy to hold up a person that is heavier? i usually am sitting down during the day, and sleeping half the day, so im not burning energy from supporting my weight from walking for example

according to this website, when i entered my current weight of 150 pounds, it recommends i eat at 1200 calories a day to lose weight
thanks!

Replies

  • Xingy01
    Xingy01 Posts: 83 Member
    Yes, this is a problem with most bmr calculators. Even the best ones are still only an estimate. They often assume more lean body mass than overweight people have.

    I use this one http://www.fat2fittools.com/tools/

    It lets you put in your body fat percentage so that there aren't assumptions about your lean body mass. The second number down under "katch-mcardle formula" is the one that takes body fat into account. For me, this showed a 900 calorie difference compared to the other method when I first started. Now it shows a 500 calorie difference.
  • yarwell
    yarwell Posts: 10,477 Member
    The estimates are curve / straight line fits to population data - often with contributions from odd populations like Italian army conscripts in 1938 (I am not joking).

    In practice two thirds of people fall within 10% of the estimate.

    Personally I think they scale badly to obese people as if you draw a straight line through the BMR to weight data of a group of light / thin people it's a hell of a stretch to extend the line out to double the weight and hope it's still valid.
  • dopeysmelly
    dopeysmelly Posts: 1,390 Member
    I found the varying estimates annoying too. I'm 5' 2" and TDEE -20% was coming up less than my BMR, and I was grappling with the "what activity level am I?" question.

    Instead I've decided to ignore all that. I've weighed myself every day (pretty much) for 3 months. I've logged my calories (most days). So, I calculated my own rough estimate for TDEE, just for me.

    ((Avg calorie intake x 93 days) + (3500 x lbs lost over 93 days))/93 = Ruth's Very Average Estimated TDEE

    OK. It assumes that all the weight I've lost is fat (hence the "3500"), but, hey, everything's an estimate anyway, and I figure this estimate is a better estimate for me..
  • ashenriver
    ashenriver Posts: 498 Member
    BMR does change based on weight, you should recalculate after every 10lbs weight loss. The calculators usually ask about body fat percentage and that is taking into consideration.

    You should use the BMR results from your current weight as a guideline.

    You didn't get different estimates, you got estimates for different weights.

    Also to consider is that the minimum MFP will give you is 1200 calories per day and that is too low for a lot of people. You should not eat less then your BMR.

    Check out this link
    http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants
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