Guest guest Posted May 11, 2006 Report Share Posted May 11, 2006 Rodney asks: " So how do we decide the optimal degree of restriction? " There was a recent message about a University of Florida study that found that just 8 percent fewer calories a day and moderately increasing activity extended the average lifespan of rats. The problem with high degrees of restriction (30%-50%) is that they are most effective when applied after weaning and they cause stunting of body size. Forty percent CR produces adult mice and rats weighing one half of the normal weight. If you take into consideration the weight of food eaten by the smaller animals, you may find that, relative to the smaller size of the restricted animals, their real rate of restriction is approximately 15%. The starvation studies by Keys, which were discussed here recently, found that severe CR decreased Basal Metabolic Rate in absolute terms by 39% and also relative to the weight of metabolically active tissue by 16%. The fact that the muscles (metabolically active tissue) can adjust by 16% means that this may represent the maximum amount of CR that should be practiced if you want to stay active and preserve your quality of life. Experience with severe caloric restriction, e.g., the famines in Somalia, has shown that a BMI less than 10 can be compatible with life with specialized care. However, don't try this for longevity. You can read about the disgusting details of severe restriction here: The limit of human adaptation to starvation. http://www.validinternational.org/tbx/docs/ACF3931.pdf Tony ============= > > Hi JW: > > The reason to drop caloric intake a little further to get a slightly > lower BMI might be the apparent indications in mice that 30% > restriction lengthens maximal lifespan by about 30%; 40% restriction > by about 40%; and 50% restriction by about 50%. These numbers are > not etched in stone, and of course we have no data at all of this > kind for humans. > > But 50% restriction is a good deal more than I am currently prepared > to inflict on misself. Especially when it seems that each 100 > calories greater restriction tends to be associated with fifteen > pounds less weight. Which suggests that at 50% restriction I might > weigh less than 100 pounds. > > But you make a good point: why should the only scientific sample we > have, WUSTL, necessarily be the be-all-and-end-all of restriction? > > So how do we decide the optimal degree of restriction? > > Perhaps by the degree of restriction that is associated with the best > set of biomarkers? > > How else? > > And do we know the optimal level for all the biomarkers? Is zero LDL- > C better than 50 LDL-C for example? Probably not? > > Rodney. > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 12, 2006 Report Share Posted May 12, 2006 Hi folks: My view on this, for what it is worth, is the following: Since many of us did not start CRON until we were 40, 50, or 60 years of age, there is no point is trying to draw any conclusions about what we should or should not be doing based on experiments in animals that were started on CRON shortly after weaning. Or even at puberty, or at any time before they were fully grown. Humans are very unlikely ever to start children on CRON before they are fully grown, so little that is relevant is likely to be learned from examining experiments in animals started very early on CR, imo. Fortunately there are at least three very serious studies where animals were started on CRON at the human-equivalent ages of middle age or later, and much can probably be learned from them. [Partridge; Spindler; Hansen.] They have all been posted here and involved fruit flies, mice and monkeys. The results of them were all broadly similar - sizeable gains in lifespan or huge reductions in mortality when CRON was started late in life - although the degrees of restriction, and the percentage expansion of lifespan varied. It is also questionable to what extent we can have any real conviction about what our set point weights or set point caloric intakes are. I used to think I knew my set point weight. At 22 when I was very athletically fit, I weighed 173 pounds, so I took that to be my setpoint. But while I was doing twenty hours a week training for endurance sports, I was also eating large amounts of food. So I now realize that my 22 year old supposed set point weight, which I had regarded as a firm number, could easily have been fifteen pounds more, or fifteen pounds less if I had put my mind to it at the time. Eating more oatmeal and drinking beer could have done it on the upside; while eating fewer potatoes would have made a big difference on the downside. So now I am coming around to the view that the only tangible, semi- scientific, way to determine the degree to which I am doing CRON successfully is by very specific and tangible measurements, done today, related to health. I have mentioned them before. Various body metrics determined by the use of a tape measure provide some idea of slimness or obesity. A study just the other day indicated that the amount of body fat around the waist shows an excellent correlation with lung function, for example. Various bio-chemical measurements of things like lipids, sugar, insulin, and so on give a broad idea of general health with regard to some of the 'diseases of aging' for which CRON appears to be a good remedy. Susceptibility to other diseases of aging is indicated by measures of inflammation - WBC and C-reactive protein for example. Hopefully there are, or will be, other good such measures. Blood pressure is, of course, another indicator that is helpful in determining health of the vascular system, and risk for heart disease, strokes and aneurysms. Now as far as I know there is still little good information to show whether one can be 'too healthy' as measured by these indicators. For example, one study suggested that risks increase at the very lowest levels of LDL. Another study found that that only applied to smokers and that there was no increased risk even at very low levels of LDL in non-smokers. But, with the qualification noted in the previous paragraph, it seems to me that looking at specific tangible measures of health, some of which are listed above, is a much better way to determine whether one is doing CRON successfully or not. Certainly much better, imo, than trying to speculate about what one's set point might be; what one's caloric intake might be now based on a supposed set point from forty years ago; and then guessing what percentage decrease in calories from that set point level might be appropriate, or in some way 'optimal'. Just my take, as JW would say. I am certainly open-minded to listen if someone believes they know a better objective way to determine whether what they are doing is reasonably close to 'optimal' or not. Rodney. > > Rodney asks: > " So how do we decide the optimal degree of restriction? " > > There was a recent message about a University of Florida study that > found that just 8 percent fewer calories a day and moderately > increasing activity extended the average lifespan of rats. > > The problem with high degrees of restriction (30%-50%) is that they > are most effective when applied after weaning and they cause stunting > of body size. Forty percent CR produces adult mice and rats weighing > one half of the normal weight. If you take into consideration the > weight of food eaten by the smaller animals, you may find that, > relative to the smaller size of the restricted animals, their real > rate of restriction is approximately 15%. > > The starvation studies by Keys, which were discussed here recently, > found that severe CR decreased Basal Metabolic Rate in absolute terms > by 39% and also relative to the weight of metabolically active tissue > by 16%. The fact that the muscles (metabolically active tissue) can > adjust by 16% means that this may represent the maximum amount of CR > that should be practiced if you want to stay active and preserve your > quality of life. > > Experience with severe caloric restriction, e.g., the famines in > Somalia, has shown that a BMI less than 10 can be compatible with life > with specialized care. However, don't try this for longevity. You > can read about the disgusting details of severe restriction here: > > The limit of human adaptation to starvation. > http://www.validinternational.org/tbx/docs/ACF3931.pdf > > Tony > > ============= > > > --- In , " Rodney " <perspect1111@> wrote: > > > > Hi JW: > > > > The reason to drop caloric intake a little further to get a slightly > > lower BMI might be the apparent indications in mice that 30% > > restriction lengthens maximal lifespan by about 30%; 40% restriction > > by about 40%; and 50% restriction by about 50%. These numbers are > > not etched in stone, and of course we have no data at all of this > > kind for humans. > > > > But 50% restriction is a good deal more than I am currently prepared > > to inflict on misself. Especially when it seems that each 100 > > calories greater restriction tends to be associated with fifteen > > pounds less weight. Which suggests that at 50% restriction I might > > weigh less than 100 pounds. > > > > But you make a good point: why should the only scientific sample we > > have, WUSTL, necessarily be the be-all-and-end-all of restriction? > > > > So how do we decide the optimal degree of restriction? > > > > Perhaps by the degree of restriction that is associated with the best > > set of biomarkers? > > > > How else? > > > > And do we know the optimal level for all the biomarkers? Is zero LDL- > > C better than 50 LDL-C for example? Probably not? > > > > Rodney. > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 12, 2006 Report Share Posted May 12, 2006 Rodney wrote: > Hi folks: > > > Now as far as I know there is still little good information to show > whether one can be 'too healthy' as measured by these indicators. > For example, one study suggested that risks increase at the very > lowest levels of LDL. Another study found that that only applied to > smokers and that there was no increased risk even at very low levels > of LDL in non-smokers. > =============== Agreed... I'm with you except that I'm inclined to argue that there is such a thing as 'too healthy' as measured by any limited subset of bio-markers since I don't have confidence in our understanding of how they all interact. If I were inclined to test a lot (I'm not) I would focus on outliers especially those known to be unhealthy. I certainly wouldn't target normal numbers for our ad-lib peers, but if you have everything well out of the red, perhaps you are done testing.... :-) JR Quote Link to comment Share on other sites More sharing options...
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