ExRx.net

Hi all
I was trying to estimate my calorie requirements using the Estimated Calorie Requirements Calculator on the website

But it seems to me that the calculator grossly overestimates calories
In fact at 150 pounds with 8 hours of sleep, 15 hours of very light activity and just one hour of moderate activity I got a total
of calories burned over BMR of 780 calories. That's a lot of calories for so little activity.

I then tested how much I would burn with 8 hours of sleep and 16 hours of very light activity, which would be "sedentary living"
That's still 541 calories burned.

To have a confirmation that was too much I tried calculating a sedentary day with the Harris-Benedict Formula
So sedentary (just like 8 hours of sleep and 16 hours of very light activity) is BMR x 1.2
My BMR is 1622. 1622 x 1.2 is 1946 calorie. If I substract my BMR I get 324 calories
Mind you, several studies have found that Harris-Benedict Formula overestimates calories by 10%

So living a sedentary life a 150 pound guy would burn 295-324 calories on top of his BMR
Seems very little but this is exactly why sedentary living is so bad.

After all it has been said many time that for an average person doing some moderate activity during the day,
the BMR is going to be the 80% of all calories burned. So activity is always more or less 20% of total calories, more often less than more.

So the calculator says that for a 150 lbs guy 1 hour of very light activity (eating, computer, talking on the phone, reading) burns 34
extra calories. But actually it's closer to 20 calories. The difference might seem little but it adds up quickly and for someone on a cut that could reset all
his calorie decifit resulting in no fat loss.

Someone 150 lbs might calculate his daily energy requirement as 2400 calories
Try to substract 500 calories for a total of 1900 calories and he should lose 1 lbs a week
But instead his daily energy requirement is 2100 calories and his calorie deficit is just 200 in truth.
He is now losing a pound every 3 weeks and practically seeing no results and giving up.

The caloric calculator is a great tool but I think the exaggerated values need to be fixed.
What do you think?

There are researchers who test this stuff and those calculations are among the best known at this time. I'm sure is a better one was available, ExRx would include it. There are a large number of factors that are not accounted for to could also affect calorie burn but to make it most complicated would reduce the value of the tool. In any case, it should only be used as a starting point and adjustments made for your specific body. The formula on the site allows you to enter BF% which should improve your accuaracy.

http://en.wikipedia.org/wiki/Basal_metabolic_rate

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
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Thanks TimD

The basal metabolic rate calculation is fine
The problem is with the estimated calories burned with activity
The Harris-Benedict and the Mifflin are the best formulas in the world and for for sedentary living they use a factor of 1.2
But with the exrx calculator a sedentary living (10 hours of sleeping, 14 hours of computer) yelds an higher result, closed to
a moderate active lifestyle. I also checked the best calculations for activities based on oxygen comsumption and indeed it was
less than the calculator provided. Like 30 instead of 38 (for activities like computer, cooking, walking to the bus) and sometimes
20 instead of 38. These errors add up quickly and one ends up with a calculated maintenance with 500 more calories than it should

Have you determined if the error is in the WHO or Durnin and Passmore figures themselves or in this adaptation. If the calculator has an error, I`m sure that that those that run this site would be interested, but if the problem is with the formula itself, that`s a different matter.

What were the exact parameters that you entered in that gave your strange results.

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
_________________
Thanks TimD

calorie estimates are always going to be a crapshoot. If you need to count things, I suggest counting grams of macros instead (grams of protein, carbs etc).

You are assuming that there is more precision in this than there is in reality. You just can't "estimate" and expect to get "exact".

_________________
Our greatest fear should not be of failure, but of succeeding at things in life that don't really matter.--Francis Chan

Andy, we know it's not accurate, but the model should be true to the theory, and although it seems to work for me, there could be a calculation error. It doesn't appear to be true to the OP but needs testing.

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
_________________
Thanks TimD

I'm talking about the Calorie Requirements calculator where you have to choose an activity for each of the 24 hours of the day
to know the total calories burned. The BMR calculation is correct.

The problem is that it overestimates the calories burned by very light, light and moderate activities.
So I tried to simulate a sedentary lifestyle with 10 hours of sleep and 14 hours of internet surfing.
The result should be that very little calories are spent doing nothing but sitting in front of the computer
In fact both the Mifflin, Harris-Benedict and WHO equations use a x1.2 factor for sedentary lifestyle.

So someone with a BMR of 1660 calories and living a sedentary lifestyle should burn, according to all equations,
1992 calories. Meaning 332 calories from activities (would you expect more from sitting the whole day?)
Sedentary lifestyle includes walking and talking. So someone doing nothing but sleeping for 10 hours and
surfing the web for 14 hours should burn even less than that. Probably 100 extra calories above BMR

But the exrx calculator for someone with a BMR of 1660 and 10 hours of sleep and 14 hours of computer yelds 2180
calories. Way more than the more active 1.2 sedentary lifestyle figure. Meaning 520 extra calories.
That's like adding a whole 2 hours workout everyday to a sedentary lifestyle, not a small difference.

Indeed the calculator thinks that 1 hour of very light activity burns 35-40 extra calories while in truth it burns 20-25 extra
calories. Seems like a small difference but it adds up quickly

If sitting at the computer is recorded as "very light" and walking is "light" then sitting would burn less than walking, however, sitting requires more energy than lying down. I think your argument is that "very light" should be less than "sedentary" which is defined as 1.2 and the calculator seems to put "very light" at more than that. I think that "sedentary" implies "resting" for much of the day which would mean less energetic than "very light".

I would suggest that if you can document that the definitions are really wrong, then send a comment to the feedback page here: http://exrx.net/Notes/Feedback.html

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
_________________
Thanks TimD

sedentary, according to Harris-Benedict, Mifflin and WHO equation, means a normal life (walking to work, working at office, cooking, sweeping the floor) but almost no physical activity or sport. So it doesn't implies resting much of the day because it would also be a non-standard lifestyle of relevance only to people in hospital, while the activity factors are supposed to represent normal life examples.

I know for sure that someone using the calculator to find maintenance calories, with a typical day as (10 hours sleeping, 10 hours very light activity, 1 hour moderate activity, 3 hours light activity) would gain weight pretty quickly with the calories suggested.

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
_________________
Thanks TimD

From what I read in the first post, I guess that you think that our body spends all its energy only on muscles and moving.
You know that the brain is the body's largest energy consumer, even in the absence of demanding tasks? That sitting can be either just trying to relax or studying or working. And in those cases it consumes even more energy.

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Don’t run if you can walk, don’t walk if you can stand, don’t stand if you can sit,
and if you sat, might as well lie down and take a nap.

No wonder I'm fat.

_________________
Our greatest fear should not be of failure, but of succeeding at things in life that don't really matter.--Francis Chan

On a tangential matter: How come the utilization (absorption) food, which varies from 97% for fat and animals proteins to 80% or so for veg. proteins and carbs (I forget where I got this number from so I might be wrong here) is not taken into the calculations? One look at NPU table like, for example, http://www.columbu.com/protein-utilization.html shows that it might amount to a substantial overestimation of proteins intake. If the figure about carbs is correct it affects the total calories intake as well.

The digestive requirements of each macro nutrient is different, and significant, and the estimate of 4 or 9 calories per gram is significantly wrong as well. These values were determined years ago by burning and measuring the heat produced. This isn't the way the body uses food. Calorie counting in general is very imprecise. As well, the body will increase burning calories in order to compensate for increased intake. What is more important is changing the amount of fat stored in the body which is only partly related to food intake. Calorie counters are only a rough guide in order to give you a place to start adjusting from.

_________________
Let thy food be thy medicine, and thy medicine be thy food.~Hippocrates
Strength is the adaptation that leads to all other adaptations that you really care about - Charles Staley
_________________
Thanks TimD