I think the calorie restriction studies deserve scrutiny. Do people who practice calorie restriction live longer compared to otherwise fit, healthy people who do not practice it? Or do they just live longer compared to the average (which includes a significant component of obese and/or diabetic over-eaters)?
This article actually answers both your questions:
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One reason for that difference could be that the WNPRC monkeys were fed an unhealthy diet, which made the calorie-restricted monkeys seem healthier by comparison simply because they ate less of it. The WNPRC monkeys’ diets contained 28.5% sucrose, compared with 3.9% sucrose at the NIA. Meanwhile, the NIA meals included fish oil and antioxidants, whereas the WNPRC meals did not. Rick Weindruch, a gerontologist at the WNPRC who led the study, admits: “Overall, our diet was probably not as healthy.”
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So, monkeys on a calorie restricted diet are not healthier than monkeys on a healthy, unrestricted diet, but are healthier than monkeys on a diet of monkey junk food.
That's the question. Actually, it is not clear that calorie restriction increases human lifespans. It works really well with fruit flies and rodents, but monkey results are mixed. I don't know if there is any direct evidence of calorie restriction increasing lifespans in humans. Actually, practicing calorie restriction when young can affect development and practicing it when old might also be dangerous due to low BMI or bone loss. And if muscle is independently associated with mortality in men then losing muscle due to controlled starvation might not be helpful either.
Calorie restriction has a far better effect on human health for average, healthy people than any other presently available tool, technique, or medical technology. That's a definitive statement that can be made from results of the existing studies, such as those under the CALERIE program.
There are no human longevity studies for the obvious reasons. The current consensus is that it won't add more than a few years to life. If it did reliably add to longevity to a significant degree, we'd already know about it for one, and secondly there are a range of evolutionary arguments for why CR produces larger effects on life span in shorter-lived species - since it evolved to adapt to famine (~= weather) conditions, which come and go on a fixed timescale depending on their cause, not one that is relative to species longevity.
Reconciling tremendous proven health benefits versus little extension of life span is one of those interesting sidebars that will fall out of the scientific process at some point.
Indeed! If you actually had the time to look for studies correlating "calorie restriction without exercise" vs "exercise only" vs both with morbidity, please share a few links of what you've found.
