Re: Maximum Safe Percentage of Caloric Restriction = 16%?

[Guest guest]

Hi Tony:

Well, maybe.

But on the other hand in 1989 thirty rhesus monkeys (fairly closely

related to humans) aged eight to fourteen at the time, were split

between an ad lib control group and a restricted group.

The restricted monkeys consumed 28% fewer calories than the controls,

and fourteen years later their weight was 26% less; they have 56%

less body fat; 12% less fat free mass; 17% less total energy

expenditure; and 20% less resting energy expenditure.

Those last two numbers indicate that the 26% lighter restricted

monkeys were considerably more active than the ad libbers. And there

were no signs that the 28% restriction is causing any problems. So

based on this experiment, the ideal degree of restriction, at least

for rhesus monkeys started on CR after maturity, seems likely to be

28% or greater. But of course the experiment has not run its

course. So we do not know yet what the average and maximal lifespans

will turn out to be for the two groups.

Some people like to embrace theoretical stuff, others find empirical

results more persuasive. I have explained before which side of that

divide I am on ; ^ )))

PMID: 12519821

Rodney.

>

> The statistics are clear that CR can help us reduce the risk of

> cardiovascular disease, diabetes, cancer, hypertension, and other

> maladies associated with aging. We all hope that CR will increase

our

> lifespan, but there have not bany many discussions about the optimum

> level of caloric restriction for humans.

>

> The graphs of the rodent data on p.48 of BT120YD indicate that

longer

> life can be achieved by greater restriction. However, what is

missing

> in Walford's book is the U-shaped curve from plotting risk of

> mortality vs. different levels of CR. At 100%CR there would be 100%

> death within a few weeks. At 80%CR the body would wither more

slowly,

> but longevity would be physiologically impossible. At 0%CR all the

> problems associated with ad libitum diets would limit longevity.

> Walford addresses the topic of the best level of CR on pp. 50-51,

but

> does not provide any concrete guidance.

>

> The rodent experiments show that 40% CR administered after weaning

> results in adults weighing only 50% of mice fed ad libitum. This

> clearly shows that a 40%CR diet can only support a half-sized body,

> and that therefore, a 40%CR diet is too severe when started

> in adulthood.

>

> The energy metabolism discussed in the Biosphere-2 paper, below,

> offers some clues that may shed light on the issue of maximum safe

> percentage of CR. The sleeping metabolic rate (SMR) for the

> biospherians was about 7% less than the controls.

>

> Keys' semistarvation studies, which are also discussed in the paper,

> showed that severe energy restriction decreased BMR in absolute

terms

> (39%) and also relative to the weight of metabolically active tissue

> (16%). However, the Biosphere paper authors conclude that the

severe

> energy restriction studied by Keys would have soon led to death by

> starvation had the study not been terminated after 6 months.

>

> So what is the maximum safe percentage of restriction? The degree

to

> which the body can adjust metabolic rate provides a good guideline.

> If you feed your body less than the amount to which it can adjust,

the

> body will try to shrink by reducing fat, muscle, or bone mass. If

16%

> is the maximum reduction in BMR for metabolically active tissues

> obtained by starvation diets, then an optimum CRON diet should not

> exceed 16%CR because the metabolism will not be able to adjust to

> fewer calories.

>

> Keys' experiment was carried out with lean subjects, so the

reference

> point for computing 16%CR shuld be a weight corresponding to a BMI

of

> around 22.

>

> Tony

> ===

>

>

> 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.

>

> http://www.ajcn.org/cgi/content/full/72/4/946

>

> " Spontaneous physical activity was significantly lower in the

> biospherians than in the control group (Table 3). The unadjusted SMR

> was 470 ± 270 kJ/d (7.9 ± 3.8%) lower in the biospherians than in

the

> control group (NS; Table 3), a difference (of 400 ± 210 kJ/d, or

6.7 ±

> 3.3%; P = 0.06) that was nearly significant after adjustment for

age,

> sex, fat-free mass, and fat mass. "

>

>

> " Some 50 y ago, Keys et al (6–8) showed in a pioneering

> semistarvation study (the Minnesota experiment) that 6 mo of severe

> energy restriction in 32 lean men led to a marked reduction in EE.

> This was due to a reduction in both physical activity and in the

> resting metabolic rate (RMR), which decreased not only in absolute

> terms (39%) but also when expressed per kilogram of metabolically

> active tissue (16%). This form of energy conservation, a

biologically

> meaningful survival mechanism in the face of dangerously low energy

> supplies and stores, has been referred to as metabolic adaptation

(6,

> 9). To date, the Minnesota experiment continues to be the most

> comprehensive underfeeding study in humans, and its findings—

revisited

> recently in detail by Dulloo et al (10–12)—have provided important

> insights into our understanding of human energy metabolism and body

> weight regulation. However, it is important to remember that the

diet

> in Keys et al's (6) study was designed to represent the severely

> energy-deficient diet in European famine areas during and after

World

> War II. Consequently, the participating lean men rapidly lost large

> amounts of weight ({approx}25% of body weight) and by the end of the

> study were severely undernourished with weakness, lethargy, and

edema

> (6, 7). Clearly, despite the adaptive reduction in EE, such severe

> energy restriction would have soon led to death by starvation had

the

> study not been terminated after 6 mo. "

>

[Guest guest]

Hi Tony:

Well, maybe.

But on the other hand in 1989 thirty rhesus monkeys (fairly closely

related to humans) aged eight to fourteen at the time, were split

between an ad lib control group and a restricted group.

The restricted monkeys consumed 28% fewer calories than the controls,

and fourteen years later their weight was 26% less; they have 56%

less body fat; 12% less fat free mass; 17% less total energy

expenditure; and 20% less resting energy expenditure.

Those last two numbers indicate that the 26% lighter restricted

monkeys were considerably more active than the ad libbers. And there

were no signs that the 28% restriction is causing any problems. So

based on this experiment, the ideal degree of restriction, at least

for rhesus monkeys started on CR after maturity, seems likely to be

28% or greater. But of course the experiment has not run its

course. So we do not know yet what the average and maximal lifespans

will turn out to be for the two groups.

Some people like to embrace theoretical stuff, others find empirical

results more persuasive. I have explained before which side of that

divide I am on ; ^ )))

PMID: 12519821

Rodney.

>

> The statistics are clear that CR can help us reduce the risk of

> cardiovascular disease, diabetes, cancer, hypertension, and other

> maladies associated with aging. We all hope that CR will increase

our

> lifespan, but there have not bany many discussions about the optimum

> level of caloric restriction for humans.

>

> The graphs of the rodent data on p.48 of BT120YD indicate that

longer

> life can be achieved by greater restriction. However, what is

missing

> in Walford's book is the U-shaped curve from plotting risk of

> mortality vs. different levels of CR. At 100%CR there would be 100%

> death within a few weeks. At 80%CR the body would wither more

slowly,

> but longevity would be physiologically impossible. At 0%CR all the

> problems associated with ad libitum diets would limit longevity.

> Walford addresses the topic of the best level of CR on pp. 50-51,

but

> does not provide any concrete guidance.

>

> The rodent experiments show that 40% CR administered after weaning

> results in adults weighing only 50% of mice fed ad libitum. This

> clearly shows that a 40%CR diet can only support a half-sized body,

> and that therefore, a 40%CR diet is too severe when started

> in adulthood.

>

> The energy metabolism discussed in the Biosphere-2 paper, below,

> offers some clues that may shed light on the issue of maximum safe

> percentage of CR. The sleeping metabolic rate (SMR) for the

> biospherians was about 7% less than the controls.

>

> Keys' semistarvation studies, which are also discussed in the paper,

> showed that severe energy restriction decreased BMR in absolute

terms

> (39%) and also relative to the weight of metabolically active tissue

> (16%). However, the Biosphere paper authors conclude that the

severe

> energy restriction studied by Keys would have soon led to death by

> starvation had the study not been terminated after 6 months.

>

> So what is the maximum safe percentage of restriction? The degree

to

> which the body can adjust metabolic rate provides a good guideline.

> If you feed your body less than the amount to which it can adjust,

the

> body will try to shrink by reducing fat, muscle, or bone mass. If

16%

> is the maximum reduction in BMR for metabolically active tissues

> obtained by starvation diets, then an optimum CRON diet should not

> exceed 16%CR because the metabolism will not be able to adjust to

> fewer calories.

>

> Keys' experiment was carried out with lean subjects, so the

reference

> point for computing 16%CR shuld be a weight corresponding to a BMI

of

> around 22.

>

> Tony

> ===

>

>

> 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.

>

> http://www.ajcn.org/cgi/content/full/72/4/946

>

> " Spontaneous physical activity was significantly lower in the

> biospherians than in the control group (Table 3). The unadjusted SMR

> was 470 ± 270 kJ/d (7.9 ± 3.8%) lower in the biospherians than in

the

> control group (NS; Table 3), a difference (of 400 ± 210 kJ/d, or

6.7 ±

> 3.3%; P = 0.06) that was nearly significant after adjustment for

age,

> sex, fat-free mass, and fat mass. "

>

>

> " Some 50 y ago, Keys et al (6–8) showed in a pioneering

> semistarvation study (the Minnesota experiment) that 6 mo of severe

> energy restriction in 32 lean men led to a marked reduction in EE.

> This was due to a reduction in both physical activity and in the

> resting metabolic rate (RMR), which decreased not only in absolute

> terms (39%) but also when expressed per kilogram of metabolically

> active tissue (16%). This form of energy conservation, a

biologically

> meaningful survival mechanism in the face of dangerously low energy

> supplies and stores, has been referred to as metabolic adaptation

(6,

> 9). To date, the Minnesota experiment continues to be the most

> comprehensive underfeeding study in humans, and its findings—

revisited

> recently in detail by Dulloo et al (10–12)—have provided important

> insights into our understanding of human energy metabolism and body

> weight regulation. However, it is important to remember that the

diet

> in Keys et al's (6) study was designed to represent the severely

> energy-deficient diet in European famine areas during and after

World

> War II. Consequently, the participating lean men rapidly lost large

> amounts of weight ({approx}25% of body weight) and by the end of the

> study were severely undernourished with weakness, lethargy, and

edema

> (6, 7). Clearly, despite the adaptive reduction in EE, such severe

> energy restriction would have soon led to death by starvation had

the

> study not been terminated after 6 mo. "

>

[Guest guest]

Rodney,

The article that you reference (PMID: 12519821) provides support for

what I am trying to say. After 10 years of 30% CR, the CR monkeys had

only a decrease of 13% REE when adjusted for fat-free mass.

http://jcem.endojournals.org/cgi/content/full/88/1/16

The 26% weight loss is equivalent to your going from a weight of 150

pounds to a weight of 113 pounds (BMI = 17).

The point that I am trying to make is that a diet that restricts more

than the body is able to compensate through improved metabolic

efficiency will result in what may be unnecessary weight loss. It

seems to me significant that in the animal and human experiments the

REE or BMR for fat-free mass decreases by 13% to 16% even in long-term

studies.

Tony

=========

> >

> > The statistics are clear that CR can help us reduce the risk of

> > cardiovascular disease, diabetes, cancer, hypertension, and other

> > maladies associated with aging. We all hope that CR will increase

> our

> > lifespan, but there have not bany many discussions about the optimum

> > level of caloric restriction for humans.

> >

> > The graphs of the rodent data on p.48 of BT120YD indicate that

> longer

> > life can be achieved by greater restriction. However, what is

> missing

> > in Walford's book is the U-shaped curve from plotting risk of

> > mortality vs. different levels of CR. At 100%CR there would be 100%

> > death within a few weeks. At 80%CR the body would wither more

> slowly,

> > but longevity would be physiologically impossible. At 0%CR all the

> > problems associated with ad libitum diets would limit longevity.

> > Walford addresses the topic of the best level of CR on pp. 50-51,

> but

> > does not provide any concrete guidance.

> >

> > The rodent experiments show that 40% CR administered after weaning

> > results in adults weighing only 50% of mice fed ad libitum. This

> > clearly shows that a 40%CR diet can only support a half-sized body,

> > and that therefore, a 40%CR diet is too severe when started

> > in adulthood.

> >

> > The energy metabolism discussed in the Biosphere-2 paper, below,

> > offers some clues that may shed light on the issue of maximum safe

> > percentage of CR. The sleeping metabolic rate (SMR) for the

> > biospherians was about 7% less than the controls.

> >

> > Keys' semistarvation studies, which are also discussed in the paper,

> > showed that severe energy restriction decreased BMR in absolute

> terms

> > (39%) and also relative to the weight of metabolically active tissue

> > (16%). However, the Biosphere paper authors conclude that the

> severe

> > energy restriction studied by Keys would have soon led to death by

> > starvation had the study not been terminated after 6 months.

> >

> > So what is the maximum safe percentage of restriction? The degree

> to

> > which the body can adjust metabolic rate provides a good guideline.

> > If you feed your body less than the amount to which it can adjust,

> the

> > body will try to shrink by reducing fat, muscle, or bone mass. If

> 16%

> > is the maximum reduction in BMR for metabolically active tissues

> > obtained by starvation diets, then an optimum CRON diet should not

> > exceed 16%CR because the metabolism will not be able to adjust to

> > fewer calories.

> >

> > Keys' experiment was carried out with lean subjects, so the

> reference

> > point for computing 16%CR shuld be a weight corresponding to a BMI

> of

> > around 22.

> >

> > Tony

> > ===

> >

> >

> > 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.

> >

> > http://www.ajcn.org/cgi/content/full/72/4/946

> >

> > " Spontaneous physical activity was significantly lower in the

> > biospherians than in the control group (Table 3). The unadjusted SMR

> > was 470 ± 270 kJ/d (7.9 ± 3.8%) lower in the biospherians than in

> the

> > control group (NS; Table 3), a difference (of 400 ± 210 kJ/d, or

> 6.7 ±

> > 3.3%; P = 0.06) that was nearly significant after adjustment for

> age,

> > sex, fat-free mass, and fat mass. "

> >

> >

> > " Some 50 y ago, Keys et al (6–8) showed in a pioneering

> > semistarvation study (the Minnesota experiment) that 6 mo of severe

> > energy restriction in 32 lean men led to a marked reduction in EE.

> > This was due to a reduction in both physical activity and in the

> > resting metabolic rate (RMR), which decreased not only in absolute

> > terms (39%) but also when expressed per kilogram of metabolically

> > active tissue (16%). This form of energy conservation, a

> biologically

> > meaningful survival mechanism in the face of dangerously low energy

> > supplies and stores, has been referred to as metabolic adaptation

> (6,

> > 9). To date, the Minnesota experiment continues to be the most

> > comprehensive underfeeding study in humans, and its findings—

> revisited

> > recently in detail by Dulloo et al (10–12)—have provided important

> > insights into our understanding of human energy metabolism and body

> > weight regulation. However, it is important to remember that the

> diet

> > in Keys et al's (6) study was designed to represent the severely

> > energy-deficient diet in European famine areas during and after

> World

> > War II. Consequently, the participating lean men rapidly lost large

> > amounts of weight ({approx}25% of body weight) and by the end of the

> > study were severely undernourished with weakness, lethargy, and

> edema

> > (6, 7). Clearly, despite the adaptive reduction in EE, such severe

> > energy restriction would have soon led to death by starvation had

> the

> > study not been terminated after 6 mo. "

> >

>

[Guest guest]

Rodney,

The article that you reference (PMID: 12519821) provides support for

what I am trying to say. After 10 years of 30% CR, the CR monkeys had

only a decrease of 13% REE when adjusted for fat-free mass.

http://jcem.endojournals.org/cgi/content/full/88/1/16

The 26% weight loss is equivalent to your going from a weight of 150

pounds to a weight of 113 pounds (BMI = 17).

The point that I am trying to make is that a diet that restricts more

than the body is able to compensate through improved metabolic

efficiency will result in what may be unnecessary weight loss. It

seems to me significant that in the animal and human experiments the

REE or BMR for fat-free mass decreases by 13% to 16% even in long-term

studies.

Tony

=========

> >

> > The statistics are clear that CR can help us reduce the risk of

> > cardiovascular disease, diabetes, cancer, hypertension, and other

> > maladies associated with aging. We all hope that CR will increase

> our

> > lifespan, but there have not bany many discussions about the optimum

> > level of caloric restriction for humans.

> >

> > The graphs of the rodent data on p.48 of BT120YD indicate that

> longer

> > life can be achieved by greater restriction. However, what is

> missing

> > in Walford's book is the U-shaped curve from plotting risk of

> > mortality vs. different levels of CR. At 100%CR there would be 100%

> > death within a few weeks. At 80%CR the body would wither more

> slowly,

> > but longevity would be physiologically impossible. At 0%CR all the

> > problems associated with ad libitum diets would limit longevity.

> > Walford addresses the topic of the best level of CR on pp. 50-51,

> but

> > does not provide any concrete guidance.

> >

> > The rodent experiments show that 40% CR administered after weaning

> > results in adults weighing only 50% of mice fed ad libitum. This

> > clearly shows that a 40%CR diet can only support a half-sized body,

> > and that therefore, a 40%CR diet is too severe when started

> > in adulthood.

> >

> > The energy metabolism discussed in the Biosphere-2 paper, below,

> > offers some clues that may shed light on the issue of maximum safe

> > percentage of CR. The sleeping metabolic rate (SMR) for the

> > biospherians was about 7% less than the controls.

> >

> > Keys' semistarvation studies, which are also discussed in the paper,

> > showed that severe energy restriction decreased BMR in absolute

> terms

> > (39%) and also relative to the weight of metabolically active tissue

> > (16%). However, the Biosphere paper authors conclude that the

> severe

> > energy restriction studied by Keys would have soon led to death by

> > starvation had the study not been terminated after 6 months.

> >

> > So what is the maximum safe percentage of restriction? The degree

> to

> > which the body can adjust metabolic rate provides a good guideline.

> > If you feed your body less than the amount to which it can adjust,

> the

> > body will try to shrink by reducing fat, muscle, or bone mass. If

> 16%

> > is the maximum reduction in BMR for metabolically active tissues

> > obtained by starvation diets, then an optimum CRON diet should not

> > exceed 16%CR because the metabolism will not be able to adjust to

> > fewer calories.

> >

> > Keys' experiment was carried out with lean subjects, so the

> reference

> > point for computing 16%CR shuld be a weight corresponding to a BMI

> of

> > around 22.

> >

> > Tony

> > ===

> >

> >

> > 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.

> >

> > http://www.ajcn.org/cgi/content/full/72/4/946

> >

> > " Spontaneous physical activity was significantly lower in the

> > biospherians than in the control group (Table 3). The unadjusted SMR

> > was 470 ± 270 kJ/d (7.9 ± 3.8%) lower in the biospherians than in

> the

> > control group (NS; Table 3), a difference (of 400 ± 210 kJ/d, or

> 6.7 ±

> > 3.3%; P = 0.06) that was nearly significant after adjustment for

> age,

> > sex, fat-free mass, and fat mass. "

> >

> >

> > " Some 50 y ago, Keys et al (6–8) showed in a pioneering

> > semistarvation study (the Minnesota experiment) that 6 mo of severe

> > energy restriction in 32 lean men led to a marked reduction in EE.

> > This was due to a reduction in both physical activity and in the

> > resting metabolic rate (RMR), which decreased not only in absolute

> > terms (39%) but also when expressed per kilogram of metabolically

> > active tissue (16%). This form of energy conservation, a

> biologically

> > meaningful survival mechanism in the face of dangerously low energy

> > supplies and stores, has been referred to as metabolic adaptation

> (6,

> > 9). To date, the Minnesota experiment continues to be the most

> > comprehensive underfeeding study in humans, and its findings—

> revisited

> > recently in detail by Dulloo et al (10–12)—have provided important

> > insights into our understanding of human energy metabolism and body

> > weight regulation. However, it is important to remember that the

> diet

> > in Keys et al's (6) study was designed to represent the severely

> > energy-deficient diet in European famine areas during and after

> World

> > War II. Consequently, the participating lean men rapidly lost large

> > amounts of weight ({approx}25% of body weight) and by the end of the

> > study were severely undernourished with weakness, lethargy, and

> edema

> > (6, 7). Clearly, despite the adaptive reduction in EE, such severe

> > energy restriction would have soon led to death by starvation had

> the

> > study not been terminated after 6 mo. "

> >

>