You have to look hard in the scientific literature to find evidence of any age-related changes made worse by the practice of calorie restriction - the only one that springs to mind right now is that progression of ALS is likely to be worsened. The much more common story is that detrimental change is resisted or attenuated: immune system aging, stem cell decline, heart aging, DNA damage, loss of health, loss of vitality, increase in risk of age-related disease ... all slowed by simply eating less while still obtaining optimal levels of nutrients. Almost everything studied by reserchers to date shows strong evidence of being made better through calorie restriction as a lifestyle choice.

Now we can add sarcopenia, age-related muscle loss, to this long list. That is counterintuitive - eating more leading to losing more muscle mass over the years - but then what is straightforward and simple in biology? Here's the abstract at PubMed:

Sarcopenia, the loss of muscle mass with normal aging, devastates quality of life - and related healthcare expenditures are enormous. The prevention or attenuation of sarcopenia would be an important medical advance.

Dietary restriction (DR) is the only dietary intervention that consistently extends median and maximum life span, as well as health span in rodents. Evidence suggests that DR will have a similar effect in primates. Furthermore, DR opposes sarcopenia in rodents.

We tested the hypothesis that DR will reduce age-related sarcopenia in a nonhuman primate. Thirty adult male rhesus monkeys, half fed a normal calorie intake and half reduced by 30% in caloric intake, were examined over 17 years for changes in [muscle mass]. Body weight-adjusted skeletal muscle mass declined somewhat in both groups but was far more rapid in the control group. We have shown that moderate, adult-onset DR can attenuate sarcopenia in a nonhuman primate model.

That would seem to shoot down the sarcopenia as dietary issue theory, in which the lower-protein diets of the elderly are supposed to cause problems. In fact, those diets should be protective, if this calorie restriction connection follows through to humans. You might also look back at evidence suggesting that sarcopenia stems from one obscure but important biochemical process becoming slowly less efficient, and that leucine supplementation from middle age onwards may reverse this growing inefficiency.

For my money, in advance of further research, I suspect that the stem cell connection is the easy answer. If calorie restriction slows the decline in stem cell activity, then the normal ongoing turnover in muscle tissue should be more readily maintained. We shall see what the real answer is in due course, but practicing calorie restriction in the meantime is still the smart thing to do.

Posted by Reason at June 20, 2008 3:52 PM | TrackBack (0)