The last time I saw my doctor for a physical, I asked him what he thought about the latest study on diet or somesuch. “I don’t pay much attention to studies,” he said gruffly, “until at least five years pass.” His point, which my own years of work with health/science stories had made evident, was that hundreds of health studies are disgorged by universities and research institutions every week—many of them contradicting previous studies. This is why The Week’s year-end roundup of health studies is labeled, “Things they said were good for us,” and “Things we were told to avoid,” with an implied “this time around.” Our recent “good for you” list included castration, which, one study found, appeared to prolong men’s lives. Any takers?
Similar skepticism is warranted in weighing last week’s most publicized study, which concluded that people who are a little overweight as measured by body mass index actually have a lower risk of dying early than people of “healthy” weight (see Science & Health). As critics have pointed out, it might be that some of the thinner people in the study were not truly healthy, but thin because they smoked or had been chronically ill, thus skewing the results. It might also be that the imprecise BMI falsely categorizes muscular workout enthusiasts as overweight. There are many possible explanations for the findings; when it comes to the complexities of human health, isolating a single cause for an observed effect is extremely difficult. So take this study, and any single study you see, with several grains of salt. That salt, by the way, may or may not give you high blood pressure. Some studies say it does. Some say it doesn’t.