Exercise Versus Calorie Restriction
The differences in a nutshell: "Calorie restriction (CR) is the only paradigm that has consistently increased lifespan in a wide variety of model organisms. Many hypotheses have been proposed as the underlying mechanism, including a reduction in body size and adiposity, which is commonly observed in calorie-restricted animals. This has led to investigations as to whether similar changes in body composition produced by increasing energy expenditure via exercise can replace or enhance the benefits of reducing energy intake. ... In rodents, the data clearly show that exercise, regardless of body weight changes, can improve health and survival, but unlike CR, fails to extend lifespan. In humans, short-term weight loss studies show that exercise and CR produce similar improvements in disease risk factors and biomarkers of aging, while some parameters clearly benefit more with exercise. Epidemiologic evidence in humans supports exercise as a strategy to reduce the risk of morbidity and mortality, but not to extend lifespan. It is unknown whether CR can extend human lifespan, but the metabolic profile of humans engaged in long-term CR shares many similarities with calorie restricted rodents and nonhuman primates. In conclusion, like CR, exercise can limit weight gain and adiposity, but only CR can extend lifespan. Therefore, in rodents, the ability of CR to slow aging is apparently more dependent on decreasing nutrient flux, rather than changes in energy balance and body composition."
I don't understand how exercise can "reduce the risk of mortality", but not extend lifespan. That seems contradictory. Would anybody like to shed some light on this?
@jordan: Look into what is called compression of morbidity. There are a number of possible ways that a mechanism might act to shift mortality off into later years, and so could be seen to reduce mortality until it doesn't any more. It could be explained away by benefits produced in periods of comparatively low cellular damage but those same benefits being blocked by consequences of higher levels of cellular damage, for example.