Re: Mifflin-St Jeor Equation

[Guest guest]

> Rodney wrote:

>

> From an email received from Dr. St. Jeor:

>

> " .......... if you extrapolate downward to reflect caloric

> deprivation, it will not be within the studied population. ...... "

>

> So perhaps we should not expect the equation to be a reliable

> indication of caloric expenditure for those who are significantly

> restricted.

>

> Rodney.

>

That is absolutely right. This is what makes the Mifflin-St Jeor

(M-S) equations an ideal reference point corresponding to " ad libitum "

eating. The difference between your actual BMR and the one calculated

by the equations provides a basis for calculating your degree of

adaptation to caloric restriction. The caloric requirements

calculated by these equations for long-term CRONies are substantially

higher than what the CRONies actually consume. For example, the M-S

requirements for Liza May are 1640 calories, but she actually eats

only 1000 calories per day.

The Biosphere-2 experiment[1] showed that the metabolic rates of the

biospherians were approximately 6% lower than those of the control

subjects after adjustment for age, sex, fat-free mass, and fat mass.

Other experiments have shown that the basal metabolic rate can

decrease by approximately 12% in three weeks of a 40% calorie

restricted diet, but without reaching material equilibrium.[2] The

six-month semistarvation study by Keys[3] showed that severe energy

restriction decreased BMR in absolute terms by 39% and also relative

to the weight of metabolically active tissue by 16%.

Experiments of overeating have also shown that several weeks of

overfeeding cause an increase in basal metabolic rate but no change in

metabolic rate during light exercise.[4] This suggests that the BMR

adapts to the level of food availability over a period of several

weeks, but it is not easily affected by demands for energy of short

duration.

Tony

===

1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

MacCallum, P Tataranni and Ravussin, " Energy metabolism

after 2 y of energy restriction: the Biosphere 2 experiment " , American

Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October 2000.

2) Friedlander AL, et al. " Three weeks of caloric restriction alters

protein metabolism in normal-weight, young men " Am J Physiol

Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

15870104

3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The biology

of human starvation " , Minneapolis: University of Minneapolis Press, 1950.

4) Welle SL, Seaton TB, RG. " Some metabolic effects of

overeating in man " , Am J Clin Nutr. 1986 Dec;44(6):718-24. PMID: 3538842

[Guest guest]

> Rodney wrote:

>

> From an email received from Dr. St. Jeor:

>

> " .......... if you extrapolate downward to reflect caloric

> deprivation, it will not be within the studied population. ...... "

>

> So perhaps we should not expect the equation to be a reliable

> indication of caloric expenditure for those who are significantly

> restricted.

>

> Rodney.

>

That is absolutely right. This is what makes the Mifflin-St Jeor

(M-S) equations an ideal reference point corresponding to " ad libitum "

eating. The difference between your actual BMR and the one calculated

by the equations provides a basis for calculating your degree of

adaptation to caloric restriction. The caloric requirements

calculated by these equations for long-term CRONies are substantially

higher than what the CRONies actually consume. For example, the M-S

requirements for Liza May are 1640 calories, but she actually eats

only 1000 calories per day.

The Biosphere-2 experiment[1] showed that the metabolic rates of the

biospherians were approximately 6% lower than those of the control

subjects after adjustment for age, sex, fat-free mass, and fat mass.

Other experiments have shown that the basal metabolic rate can

decrease by approximately 12% in three weeks of a 40% calorie

restricted diet, but without reaching material equilibrium.[2] The

six-month semistarvation study by Keys[3] showed that severe energy

restriction decreased BMR in absolute terms by 39% and also relative

to the weight of metabolically active tissue by 16%.

Experiments of overeating have also shown that several weeks of

overfeeding cause an increase in basal metabolic rate but no change in

metabolic rate during light exercise.[4] This suggests that the BMR

adapts to the level of food availability over a period of several

weeks, but it is not easily affected by demands for energy of short

duration.

Tony

===

1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

MacCallum, P Tataranni and Ravussin, " Energy metabolism

after 2 y of energy restriction: the Biosphere 2 experiment " , American

Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October 2000.

2) Friedlander AL, et al. " Three weeks of caloric restriction alters

protein metabolism in normal-weight, young men " Am J Physiol

Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

15870104

3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The biology

of human starvation " , Minneapolis: University of Minneapolis Press, 1950.

4) Welle SL, Seaton TB, RG. " Some metabolic effects of

overeating in man " , Am J Clin Nutr. 1986 Dec;44(6):718-24. PMID: 3538842

[Guest guest]

Hi Tony:

Well I am somewhat confused about this issue on a number of counts.

First, about a year ago someone posted here under a subject heading

something like: " What is CR, Eating 18% More Food? " making the case

that per unit of active body mass people on CR were eating more

calories. Part of the evidence for that was that mice which consumed

40% less food weighed 50% less. What you write here appears to

disagree with that.

Second, I have not read the original Mifflin-St. Jeor paper, but I

assume that to derive their equation they surveyed people who ranged

at least from the moderately obese (BMI = 30 - 35, there are plenty

of them around to survey) down to 'normal' (BMI = 20 - 25). So the

greater metabolic efficiency per unit of active body mass apparently

exhibited by slimmer people should, one might suppose, already be

incorporated into the slope of the curve of weight versus caloric

intake implied by the Mifflin-St.Jeor Equation (MSJE). Clearly if,

as I have previously noted, a human on 40% restriction should,

according to the MSJE, weigh 57 pounds with a BMI of 7.7, but does

not, then this supposition is not correct either.

Third, one might be tempted to hypothesize that energy expenditure

would be found to be consistent with a 'corporate economics' view of

things, where there are fixed costs (in the case of an organism fixed

energy costs) and variable (energy) costs. So in the organism's

case, as body weight falls, only the variable energy costs fall as

the very most basic (fixed) energy demands (brain function, for

example) do not decline because they must continue in order for the

organism to stay alive. The result being that as body weight

declines only a portion of energy expenditure delines proportionally

with weight, while the fixed portion remains constant. However,

logical as that might sound, unfortunately the opposite seems to be

true, at least at lower weights in comparison with MSJE predictions.

Fourth, another possibility is that the assumptions about the energy

usage of each metabolic component (fat, bone, brain, muscle, etc.),

used in some studies for calculating variations in total energy

expenditure with weight, may be wrong. I realize this will appear

unlikely, but since about 65% of weight lost is fat mass, if fat were

(secretly apparently) a particularly heavy user of energy, then the

larger reduction in energy usage compared with weight lost might be

explained. Of course no one presently believes this to be true. But

certainly the improved energy efficiency observed to accompany weight

loss could be explained if the major body mass components being lost

are those that are the most intense energy users.

Or perhaps the energy needed for movement is the key factor? Then as

weight is lost a huge reduction might occur in energy expenditure

simply from the reduction in regular day-to-day movement ........

getting out of bed, walking to the refridgerator, walking to the

garage, etc.?

And for the lower weight individual with less insulation and larger

surface area/volume ratio one would expect decreased energy

efficiency, so that cannot be the explanation. Is the lowered body

temperature of people on CRON enough to explain it? Or is that

merely a symptom of the lack of insulation and surface/volume issues

noted?

Anyway, whatever the facts underlying relationships between caloric

intake and body weight, and how best to explain them, it seems the

conclusion to be drawn from this, if there is one, is for people

pursuing CR not to use either -Benedict or Mifflin-St.Jeor to

estimate where their weight will eventually stabilize at some

targeted level of caloric intake - which was what I had been trying

to do when I get into this mess in the first place!

Rodney.

> >

> > From an email received from Dr. St. Jeor:

> >

> > " .......... if you extrapolate downward to reflect caloric

> > deprivation, it will not be within the studied

population. ...... "

> >

> > So perhaps we should not expect the equation to be a reliable

> > indication of caloric expenditure for those who are significantly

> > restricted.

> >

> > Rodney.

> >

>

> That is absolutely right. This is what makes the Mifflin-St Jeor

> (M-S) equations an ideal reference point corresponding to " ad

libitum "

> eating. The difference between your actual BMR and the one

calculated

> by the equations provides a basis for calculating your degree of

> adaptation to caloric restriction. The caloric requirements

> calculated by these equations for long-term CRONies are

substantially

> higher than what the CRONies actually consume. For example, the M-S

> requirements for Liza May are 1640 calories, but she actually eats

> only 1000 calories per day.

>

> The Biosphere-2 experiment[1] showed that the metabolic rates of the

> biospherians were approximately 6% lower than those of the control

> subjects after adjustment for age, sex, fat-free mass, and fat

mass.

> Other experiments have shown that the basal metabolic rate can

> decrease by approximately 12% in three weeks of a 40% calorie

> restricted diet, but without reaching material equilibrium.[2] The

> six-month semistarvation study by Keys[3] showed that severe energy

> restriction decreased BMR in absolute terms by 39% and also relative

> to the weight of metabolically active tissue by 16%.

>

> Experiments of overeating have also shown that several weeks of

> overfeeding cause an increase in basal metabolic rate but no change

in

> metabolic rate during light exercise.[4] This suggests that the BMR

> adapts to the level of food availability over a period of several

> weeks, but it is not easily affected by demands for energy of short

> duration.

>

> Tony

> ===

>

> 1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

> MacCallum, P Tataranni and Ravussin, " Energy metabolism

> after 2 y of energy restriction: the Biosphere 2 experiment " ,

American

> Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October

2000.

>

> 2) Friedlander AL, et al. " Three weeks of caloric restriction alters

> protein metabolism in normal-weight, young men " Am J Physiol

> Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

> 15870104

>

> 3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The

biology

> of human starvation " , Minneapolis: University of Minneapolis Press,

1950.

>

> 4) Welle SL, Seaton TB, RG. " Some metabolic effects of

> overeating in man " , Am J Clin Nutr. 1986 Dec;44(6):718-24. PMID:

3538842

>

[Guest guest]

Hi Tony:

Well I am somewhat confused about this issue on a number of counts.

First, about a year ago someone posted here under a subject heading

something like: " What is CR, Eating 18% More Food? " making the case

that per unit of active body mass people on CR were eating more

calories. Part of the evidence for that was that mice which consumed

40% less food weighed 50% less. What you write here appears to

disagree with that.

Second, I have not read the original Mifflin-St. Jeor paper, but I

assume that to derive their equation they surveyed people who ranged

at least from the moderately obese (BMI = 30 - 35, there are plenty

of them around to survey) down to 'normal' (BMI = 20 - 25). So the

greater metabolic efficiency per unit of active body mass apparently

exhibited by slimmer people should, one might suppose, already be

incorporated into the slope of the curve of weight versus caloric

intake implied by the Mifflin-St.Jeor Equation (MSJE). Clearly if,

as I have previously noted, a human on 40% restriction should,

according to the MSJE, weigh 57 pounds with a BMI of 7.7, but does

not, then this supposition is not correct either.

Third, one might be tempted to hypothesize that energy expenditure

would be found to be consistent with a 'corporate economics' view of

things, where there are fixed costs (in the case of an organism fixed

energy costs) and variable (energy) costs. So in the organism's

case, as body weight falls, only the variable energy costs fall as

the very most basic (fixed) energy demands (brain function, for

example) do not decline because they must continue in order for the

organism to stay alive. The result being that as body weight

declines only a portion of energy expenditure delines proportionally

with weight, while the fixed portion remains constant. However,

logical as that might sound, unfortunately the opposite seems to be

true, at least at lower weights in comparison with MSJE predictions.

Fourth, another possibility is that the assumptions about the energy

usage of each metabolic component (fat, bone, brain, muscle, etc.),

used in some studies for calculating variations in total energy

expenditure with weight, may be wrong. I realize this will appear

unlikely, but since about 65% of weight lost is fat mass, if fat were

(secretly apparently) a particularly heavy user of energy, then the

larger reduction in energy usage compared with weight lost might be

explained. Of course no one presently believes this to be true. But

certainly the improved energy efficiency observed to accompany weight

loss could be explained if the major body mass components being lost

are those that are the most intense energy users.

Or perhaps the energy needed for movement is the key factor? Then as

weight is lost a huge reduction might occur in energy expenditure

simply from the reduction in regular day-to-day movement ........

getting out of bed, walking to the refridgerator, walking to the

garage, etc.?

And for the lower weight individual with less insulation and larger

surface area/volume ratio one would expect decreased energy

efficiency, so that cannot be the explanation. Is the lowered body

temperature of people on CRON enough to explain it? Or is that

merely a symptom of the lack of insulation and surface/volume issues

noted?

Anyway, whatever the facts underlying relationships between caloric

intake and body weight, and how best to explain them, it seems the

conclusion to be drawn from this, if there is one, is for people

pursuing CR not to use either -Benedict or Mifflin-St.Jeor to

estimate where their weight will eventually stabilize at some

targeted level of caloric intake - which was what I had been trying

to do when I get into this mess in the first place!

Rodney.

> >

> > From an email received from Dr. St. Jeor:

> >

> > " .......... if you extrapolate downward to reflect caloric

> > deprivation, it will not be within the studied

population. ...... "

> >

> > So perhaps we should not expect the equation to be a reliable

> > indication of caloric expenditure for those who are significantly

> > restricted.

> >

> > Rodney.

> >

>

> That is absolutely right. This is what makes the Mifflin-St Jeor

> (M-S) equations an ideal reference point corresponding to " ad

libitum "

> eating. The difference between your actual BMR and the one

calculated

> by the equations provides a basis for calculating your degree of

> adaptation to caloric restriction. The caloric requirements

> calculated by these equations for long-term CRONies are

substantially

> higher than what the CRONies actually consume. For example, the M-S

> requirements for Liza May are 1640 calories, but she actually eats

> only 1000 calories per day.

>

> The Biosphere-2 experiment[1] showed that the metabolic rates of the

> biospherians were approximately 6% lower than those of the control

> subjects after adjustment for age, sex, fat-free mass, and fat

mass.

> Other experiments have shown that the basal metabolic rate can

> decrease by approximately 12% in three weeks of a 40% calorie

> restricted diet, but without reaching material equilibrium.[2] The

> six-month semistarvation study by Keys[3] showed that severe energy

> restriction decreased BMR in absolute terms by 39% and also relative

> to the weight of metabolically active tissue by 16%.

>

> Experiments of overeating have also shown that several weeks of

> overfeeding cause an increase in basal metabolic rate but no change

in

> metabolic rate during light exercise.[4] This suggests that the BMR

> adapts to the level of food availability over a period of several

> weeks, but it is not easily affected by demands for energy of short

> duration.

>

> Tony

> ===

>

> 1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

> MacCallum, P Tataranni and Ravussin, " Energy metabolism

> after 2 y of energy restriction: the Biosphere 2 experiment " ,

American

> Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October

2000.

>

> 2) Friedlander AL, et al. " Three weeks of caloric restriction alters

> protein metabolism in normal-weight, young men " Am J Physiol

> Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

> 15870104

>

> 3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The

biology

> of human starvation " , Minneapolis: University of Minneapolis Press,

1950.

>

> 4) Welle SL, Seaton TB, RG. " Some metabolic effects of

> overeating in man " , Am J Clin Nutr. 1986 Dec;44(6):718-24. PMID:

3538842

>

[Guest guest]

That is true of Benedict also, I'm sure. I can change my "meatbolism". (pun accidental but quite funny.) I can eat at least 400 kcals more at 98.6 deg, compare to 97.4, without weight gain, so that blows any equation based on "standard" data.

WE CAN'T mathematically extrapolate any data outside the bounds for which the function was determined/analyzed.

Regards.

[ ] Mifflin-St Jeor Equation

From an email received from Dr. St. Jeor:".......... if you extrapolate downward to reflect caloric deprivation, it will not be within the studied population. ...... "So perhaps we should not expect the equation to be a reliable indication of caloric expenditure for those who are significantly restricted.Rodney.

[Guest guest]

That is true of Benedict also, I'm sure. I can change my "meatbolism". (pun accidental but quite funny.) I can eat at least 400 kcals more at 98.6 deg, compare to 97.4, without weight gain, so that blows any equation based on "standard" data.

WE CAN'T mathematically extrapolate any data outside the bounds for which the function was determined/analyzed.

Regards.

[ ] Mifflin-St Jeor Equation

From an email received from Dr. St. Jeor:".......... if you extrapolate downward to reflect caloric deprivation, it will not be within the studied population. ...... "So perhaps we should not expect the equation to be a reliable indication of caloric expenditure for those who are significantly restricted.Rodney.

[Guest guest]

Rodney,

I was the author of the " 18% more food " note. As you are well aware,

quantitative theoretical study of Caloric Restriction is lagging far

behind the practice.

Mattson's 40% restricted mice had about half (0.51) the weight of ad

libitum mice. If the AL mice get F grams of food for a body weight of

W, the CR mice get 0.6 F grams of food for a body weight of 0.51 W.

Dividing 0.6 F by 0.51 W gives 1.18 food/weight for the CR mice, which

is 18% more food.

This is paradoxical, unless the restricted mice have a metabolic

capacity that decreases at a slower rate than their decrease in size.

In this way, they will still be eating less than they need (still

calorically restricted) even though they are eating relatively more on

a weight basis. I have some equations for metabolic capacity at the

bottom of my CR web page:

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

I think that you are right that the -Benedict or Mifflin-St.Jeor

cannot be used to estimate where the weight of a person practicing CR

will eventually stabilize because you get outside the range of the " ad

libitum " metabolism from which the equations were derived (M-S PMID:

2305711).

However, applying the Mifflin-St Jeor energy expenditure equations to

human data we can find some correlation with the mouse data. Given a

5-foot, 8-inch (1.73 m) 35-year-old human male with a BMI of 22.0

(144.4 pounds, 65.5 kg), the Basal Metabolic Rate (BMR) is 1565

Calories, and 2153 Calories if lightly active. A person of half the

weight (72.2 pound, 32.8 kg) and a height of 4 feet, 0 inches (1.22

m), also corresponding to a BMI of 22.0, would have a BMR of 919

Calories, and 1263 calories if lightly active. Notice that the caloric

requirements for a person of half the weight are not half of the

requirements of the full-grown person, but rather 59 percent, which

corresponds to a 40% CR diet!

This is a very interesting coincidence. Maybe humans are not that

different from mice.

Tony

> > >

> > > From an email received from Dr. St. Jeor:

> > >

> > > " .......... if you extrapolate downward to reflect caloric

> > > deprivation, it will not be within the studied

> population. ...... "

> > >

> > > So perhaps we should not expect the equation to be a reliable

> > > indication of caloric expenditure for those who are significantly

> > > restricted.

> > >

> > > Rodney.

> > >

> >

> > That is absolutely right. This is what makes the Mifflin-St Jeor

> > (M-S) equations an ideal reference point corresponding to " ad

> libitum "

> > eating. The difference between your actual BMR and the one

> calculated

> > by the equations provides a basis for calculating your degree of

> > adaptation to caloric restriction. The caloric requirements

> > calculated by these equations for long-term CRONies are

> substantially

> > higher than what the CRONies actually consume. For example, the M-S

> > requirements for Liza May are 1640 calories, but she actually eats

> > only 1000 calories per day.

> >

> > The Biosphere-2 experiment[1] showed that the metabolic rates of the

> > biospherians were approximately 6% lower than those of the control

> > subjects after adjustment for age, sex, fat-free mass, and fat

> mass.

> > Other experiments have shown that the basal metabolic rate can

> > decrease by approximately 12% in three weeks of a 40% calorie

> > restricted diet, but without reaching material equilibrium.[2] The

> > six-month semistarvation study by Keys[3] showed that severe energy

> > restriction decreased BMR in absolute terms by 39% and also relative

> > to the weight of metabolically active tissue by 16%.

> >

> > Experiments of overeating have also shown that several weeks of

> > overfeeding cause an increase in basal metabolic rate but no change

> in

> > metabolic rate during light exercise.[4] This suggests that the BMR

> > adapts to the level of food availability over a period of several

> > weeks, but it is not easily affected by demands for energy of short

> > duration.

> >

> > Tony

> > ===

> >

> > 1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

> > MacCallum, P Tataranni and Ravussin, " Energy metabolism

> > after 2 y of energy restriction: the Biosphere 2 experiment " ,

> American

> > Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October

> 2000.

> >

> > 2) Friedlander AL, et al. " Three weeks of caloric restriction alters

> > protein metabolism in normal-weight, young men " Am J Physiol

> > Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

> > 15870104

> >

> > 3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The

> biology

> > of human starvation " , Minneapolis: University of Minneapolis Press,

> 1950.

> >

> > 4) Welle SL, Seaton TB, RG. " Some metabolic effects of

> > overeating in man " , Am J Clin Nutr. 1986 Dec;44(6):718-24. PMID:

> 3538842

> >

>

[Guest guest]

Rodney,

I was the author of the " 18% more food " note. As you are well aware,

quantitative theoretical study of Caloric Restriction is lagging far

behind the practice.

Mattson's 40% restricted mice had about half (0.51) the weight of ad

libitum mice. If the AL mice get F grams of food for a body weight of

W, the CR mice get 0.6 F grams of food for a body weight of 0.51 W.

Dividing 0.6 F by 0.51 W gives 1.18 food/weight for the CR mice, which

is 18% more food.

This is paradoxical, unless the restricted mice have a metabolic

capacity that decreases at a slower rate than their decrease in size.

In this way, they will still be eating less than they need (still

calorically restricted) even though they are eating relatively more on

a weight basis. I have some equations for metabolic capacity at the

bottom of my CR web page:

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

I think that you are right that the -Benedict or Mifflin-St.Jeor

cannot be used to estimate where the weight of a person practicing CR

will eventually stabilize because you get outside the range of the " ad

libitum " metabolism from which the equations were derived (M-S PMID:

2305711).

However, applying the Mifflin-St Jeor energy expenditure equations to

human data we can find some correlation with the mouse data. Given a

5-foot, 8-inch (1.73 m) 35-year-old human male with a BMI of 22.0

(144.4 pounds, 65.5 kg), the Basal Metabolic Rate (BMR) is 1565

Calories, and 2153 Calories if lightly active. A person of half the

weight (72.2 pound, 32.8 kg) and a height of 4 feet, 0 inches (1.22

m), also corresponding to a BMI of 22.0, would have a BMR of 919

Calories, and 1263 calories if lightly active. Notice that the caloric

requirements for a person of half the weight are not half of the

requirements of the full-grown person, but rather 59 percent, which

corresponds to a 40% CR diet!

This is a very interesting coincidence. Maybe humans are not that

different from mice.

Tony

> > >

> > > From an email received from Dr. St. Jeor:

> > >

> > > " .......... if you extrapolate downward to reflect caloric

> > > deprivation, it will not be within the studied

> population. ...... "

> > >

> > > So perhaps we should not expect the equation to be a reliable

> > > indication of caloric expenditure for those who are significantly

> > > restricted.

> > >

> > > Rodney.

> > >

> >

> > That is absolutely right. This is what makes the Mifflin-St Jeor

> > (M-S) equations an ideal reference point corresponding to " ad

> libitum "

> > eating. The difference between your actual BMR and the one

> calculated

> > by the equations provides a basis for calculating your degree of

> > adaptation to caloric restriction. The caloric requirements

> > calculated by these equations for long-term CRONies are

> substantially

> > higher than what the CRONies actually consume. For example, the M-S

> > requirements for Liza May are 1640 calories, but she actually eats

> > only 1000 calories per day.

> >

> > The Biosphere-2 experiment[1] showed that the metabolic rates of the

> > biospherians were approximately 6% lower than those of the control

> > subjects after adjustment for age, sex, fat-free mass, and fat

> mass.

> > Other experiments have shown that the basal metabolic rate can

> > decrease by approximately 12% in three weeks of a 40% calorie

> > restricted diet, but without reaching material equilibrium.[2] The

> > six-month semistarvation study by Keys[3] showed that severe energy

> > restriction decreased BMR in absolute terms by 39% and also relative

> > to the weight of metabolically active tissue by 16%.

> >

> > Experiments of overeating have also shown that several weeks of

> > overfeeding cause an increase in basal metabolic rate but no change

> in

> > metabolic rate during light exercise.[4] This suggests that the BMR

> > adapts to the level of food availability over a period of several

> > weeks, but it is not easily affected by demands for energy of short

> > duration.

> >

> > Tony

> > ===

> >

> > 1) Christian Weyer, Roy L Walford, Inge T Harper, Mike Milner, Taber

> > MacCallum, P Tataranni and Ravussin, " Energy metabolism

> > after 2 y of energy restriction: the Biosphere 2 experiment " ,

> American

> > Journal of Clinical Nutrition, Vol. 72, No. 4, 946-953, October

> 2000.

> >

> > 2) Friedlander AL, et al. " Three weeks of caloric restriction alters

> > protein metabolism in normal-weight, young men " Am J Physiol

> > Endocrinol Metab., 2005 Sep;289(3):E446-55. Epub 2005 May 3. PMID:

> > 15870104

> >

> > 3) Keys A, Brozek J, Henschel A, Mickelsen O, HL. " The

> biology

> > of human starvation " , Minneapolis: University of Minneapolis Press,

> 1950.

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