%CR and body size (was Accuracy of Formulas...)

[Guest guest]

> " Rodney " <perspect1111@...> wrote:

> You often make this claim - that mice on 40% CR grow to being half

> the size of mice fed ad lib. But am I right in believing that that

> is only true if the mice are put on CR at a very early age, like

> shortly after weaning?

>

> And if I am correct about that, then why do you believe this has

> relevance to humans? I have never seen or heard of anyone say they

> were put on CR shortly after weaning; nor have I seen anyone say

> they

> are thinking of doing it with their child; and certainly no one I am

> aware of who knows anything about CR recommends such a practice. So

> what is it about this mouse example that you feel has relevance for

> people at ?

>

> I very much doubt anyone here would recommend even considering

> starting CR at least until they have become fully grown on a regular

> diet.

>

Rodney,

It is a fact that mice on 40% CR grow to being half the size of mice

fed ad lib. Just look at the Figure 1 of Mattson's paper:

http://www.pnas.org/cgi/content/full/100/10/6216

A high degree of Caloric Restriction stunts growth when applied from

an early age. Why is this relevant for the people at ?

Here is my opinion:

In nature everything seeks its balance. If you plant a maple seedling

in a 1 gallon pot, you will have a small bonsai at the end of 15

years. If you plant an identical seedling in a field, you will have a

30-foot full grown tree in 15 years. The resources available to the

tree determine its development. CR works in the same way. The amount

of nutrients available (the environmental factors) supersede the

genetic factors that control growth.

If we plant the bonsai in a field after 15 years, the tree will grow

further. A person who starts eating ad lib after being on CR will

start to gain weight.

However, if you try to restrict the resources of the full-size tree to

those of a smaller tree, the big tree can readily wither or die. Call

it " transplant shock " or whatever. I think that something similar can

happen with humans if the degree of caloric restriction is too great.

There will be a loss of weight as the muscles shrink, the bone mass

diminishes, and maybe even as the brain fat is depleted.

If you take a look at the Mifflin-St Jeor energy equations for a

5-foot, 8-inch 35-year-old human male with a BMI of 22.0, the BMR is

1565 Calories. A person of half the weight (72.2 pounds) and a height

of 4 feet, 0 inches, also corresponding to a BMI of 22.0, would have a

BMR of 919 Calories. Calculating the percentage: 100(919/1565), we

get 59 percent. Surprise! A half-size human requires ~60% of the

calories of the full-size human, i.e., a 40%CR diet. Is it only

coincidence that this is the same as the mouse data? I don't think so.

So what happens if a full size mature human starts eating the diet for

a half-size human? Keys' Minnesota starvation studies provide the

answer. The body adapts by consuming its own tissues and reducing the

BMR of metabolically active tissue by up to 16%. If the caloric

restriction exceeds the amount by which the body can adjust its

metabolism, the body starts wasting away, and you eventually starve to

death if a balance is not reached. I think that CR beyond the ability

of the body to adapt will cause more harm than good. I don't think

that any adult should adopt CR diets in excess of 16 or 17 percent.

That is my opinion. I have some of this information with references

on my CR page.

http://www.scientificpsychic.com/health/crondiet.html

Tony