Calorie restricted diets.

How is the thoughtful reader supposed to interpret Gina Kolata's New York Times story about the newly reported findings that calorie restricted (20% or more below typical intake) diets do not extend life, at least not in monkeys? Earlier studies of mice and other primates had shown promising results, and there is at least one study of the effects of calorie restricted diets in humans underway.

The article includes several useful hints:
  •  Replication is key to the scientific method, and failure to replicate a result means that the original study may have had flaws. In fact, as Kolata reports, the original study had several flaws, notably that deaths among younger monkeys in the earlier study were excluded from the study.
  • The new study suggests that restricted calorie diets may have some beneficial health results: older monkeys put on the diet had lower levels of triglycerides. Monkeys put on the diet when they were younger had less cancer. That's an interesting result, but might it result from what the monkeys were fed rather than the amount? According to the news reports, that question remains unanswered.

Some people have decided to start eating less as a result of early reports. And others simply refuse to believe the results of the new studies. I think that it's too soon to tell, though the failure to replicate the results is suggestive. I'd also like to know more about the content of the diets beyond the restriction in calories. It will be interesting to see what the human study reports.

What do you think? I'd be interested in learning others' thoughts in the comments.

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