Sensitivity of Weight to Caloric Intake

[Guest guest]

Hi folks:

OK. As promised (threatened?) here are the calculations behind

the 'fifteen-pounds-weight-change-per-hundred-incremental-calories'

number I mentioned in a previous post.

The Mifflin-St Jeor equations relate resting energy expenditure (REE)

to gender, weight, height and age. For males the formula is:

REE = (10 x weight kg) + (6.25 x height cm) - (5 x age years) + 5

Naturally, with a bit of very simple algebraic rearrangement the same

formula can be modified to show weight as a function of gender, REE,

height and age. For simplicity I took the data for gender, height

and age for me which greatly condensed the equation to:

My weight in pounds = (REE-807.5)/4.536

[Of course I am relying on the assumption that the scientifically

determined Mifflin-St Jeor equation is accurate - if not precisely

accurate at every level of caloric intake, at least for what it says

about shifts in weight in relation to changes in intake.]

One slight complication is that we do not consume a resting energy

expenditure number of calories because we all exert ourselves

physically to varying degrees. So, I took each of the total caloric

intake data points shown in the first column in the table below,

calculated what the corresponding number was when activity-related

calories were excluded (second column) then used the 'My weight in

pounds' formula above to calculate the Mifflin-St Jeor corresponding

weight (column 3) - assuming, of course, 'all else equal' - that is,

that the only thing changed is caloric intake. I did this for two

cases ....... in the first case assuming light activity (gross up

factor 1.375), and moderate activity (gross up factor 1.55) for the

second case. Then I averaged the results.

Then I took the data for rows three, four and five in the tables as

representing a range likely to encompass the weight loss experience

of most males as they approach a CRON weight - from 223 pounds down

to 143 pounds. That 80 pound weight loss (from column 3) is

associated with a 500 reduction in calories consumed (2500 to 2000,

from column 1), including those related to light physical activity.

That is a sixteen pound change per hundred calories.

Then I did the same calculations assuming moderate activity. This

time the change of weight with caloric intake came out as 14.2 pounds

per hundred calories - data not shown. Hopefully the table will

format well enough to be able to read. We will see!

Analysis for Moderate Activity Level

------------------------------------

Caloric Intake........Equilib

--------------.........weight

Total......REE....... --------

-----.....----.......

....(calories).........(pounds)

1500......1091............62

1750......1273...........103

2000......1455...........143

2250......1636...........183

2500......1818...........223

2750......2000...........263

3000......2182...........303

3250......2364...........343

3500......2545...........383

3750......2727...........423

4000......2909...........463

So, if the Mifflin/St Jeor equations are reasonably close to the

mark, and I have no reason to think otherwise, then the sensitivity

is fifteen pounds per hundred calories.

Rodney.