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Accuracy of TDEE & BMR calculators

(8 Posts)
lljkk Sun 31-Dec-17 14:18:44

I googled for this, but not clear answer.

Very sorry if this sounds like a brag, please hide if it annoys you. I only post b/c I'm puzzled. I know some MNers are passionate about these calculators.

I get about 90 minutes of exercise on average (per day), but only half of that (at most) is 'intense'. Rest is walking, gardening, easy cycling, etc.

So my BMR is ~1300 kcal/day. I eat about double that but don't gain weight over time (BMI stays about 21). Even though I have a sedentary job & am mostly sedentary at home. My calc'd TDEE ranges 1600 to 2300 depending how to interpret the questions.

I gather TDEE is part guesswork, but most online threads complain it's too high, not too low a guess. Could it be just plain wildly wrong for some otherwise 'normal*' people?

*meaning no metabolic disorder, chronic illness or similar explanation.

OP’s posts: |
IMightMentionGriddlebone Sun 31-Dec-17 20:02:21

I've read it's normal to vary +/-250 calories from a good (correct data used, original formula calculated after studying people like you) TDEE prediction.

The most accurate way to calculate your actual TDEE is to weigh everything you eat for about three months, and carefully record your own weight over the same time frame and see if it goes up or down. It'll help if you wear some kind of expensive gadget 24/7 to assess whether your activity remains constant.

Online calculators are a ballpark figure in the first place, and the innate problem there is only exacerbated by the fact many people are... unreliable narrators. Active people tend to underestimate their own activity. Inactive people, conversely, over-estimate their activity. Loads of people bring their own issues with food to the table when they try to reflect on what lifestyle they have, and what lifestyle they should have.

What type of food you eat might play a part. There has been some research to suggest that cooking/not cooking food changes how accessible the calories are. For example, someone who eats a great deal of raw food might, on paper, be consuming a great deal of calories and yet not be gaining weight, and seem to have a very high TDEE. But it might be that they're not actually consuming that many calories after all.

IMightMentionGriddlebone Sun 31-Dec-17 20:15:05

P.S. I doubt very much that you're sedentary. If you have 90 minutes of purposeful activity that you're aware of and think you're sedentary, that suggests you're under-estimating your activity level in general.

I have a really good article somewhere that describes the activity levels and how to determine your own for the purpose of TDEE calcs. Give me a couple of hours...

lljkk Sun 31-Dec-17 20:17:46

Ta 4 reply.
Yeah I saw New Scientist article about differences due to raw vs. cooked (I barely eat anything raw, though). No Fing way I'm weighing all my food. I'm not THAT curious.

It may be that I always ate more than other people. I kept an activity log over past yr but the log software doesn't seem to calc calories expended. I run 11 minute miles. Hardly a paragon of fitness.

OP’s posts: |
lljkk Sun 31-Dec-17 20:19:38

(xpost). Truly is sedentary. Most of my activity at home or at work involves trips to the kettle!! And then to the loo

Reminds me, I've been hours too long on lappy & it's time to heave the cat to someone else's lap. There's a book shelf that needs sorting.

OP’s posts: |
IMightMentionGriddlebone Sun 31-Dec-17 20:26:37

Sedentary: Sometimes under the care of someone else. Resting
metabolic rate plus a factor for minimal activities - playing cards, watching TV, reading, etc.

Lightly Active: Most students, office workers, and professionals;
lawyers, doctors, shop workers, teachers, drivers, lab workers, playing a
musical instrument, housewives/househusbands with mechanical
appliances, unemployed persons. This includes eight hours sleep and 16
hours of sitting or standing. Three of the 16 hours must include light
activity (walking, laundry, golf, ping pong) and one hour must be
moderate activity (tennis, dancing, walking briskly, aerobics, etc.).

Moderately Active: Most persons in light industry, electrical,
carpentry and building trades (excluding heavy laborers), many farm
workers, soldiers not in active service, commercial fishermen,
housewives/househusbands without mechanical appliances. If you have an
office or driving occupation (see Lightly Active category), you may have
to average 1.5 to 2 hours of exercise per day (like jogging 5 to 6
miles/day) to be "Moderately Active."

Very Active: Full time athletes, unskilled laborers, some agricultural
workers (especially peasant farming), forestry workers, army recruits and
soldiers in active service, mine workers, steel workers. This level requires
moderate intensity activity for most of the work day or exercise
comparable to running 9 to 13 miles/day.

Extremely Active: Lumberjacks, blacksmiths, female construction
workers, heavy manual digging, rickshaw pullers, and coal mining.
Moderate to high level of physical activity for most of the work day or

lljkk Sun 31-Dec-17 21:47:52

Ta. My job is sitting, reading & typing and making cups of tea. Not a lot busier at home, but maybe I can move into the "Moderately Active" list due to 90 min exercise on avg?
That seems to give a TDEE around 2k. Still well below what I actually eat.

OP’s posts: |
lljkk Sun 31-Dec-17 21:48:46

how much does sleep matter? I might lie in bed for 10 hrs but don't get more than 6 asleep.

OP’s posts: |

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