In an extraordinary editorial and feature article, Nature, one of the world’s pre-eminent scientific journals, has effectively
NEW YORK - JULY 24: Walter Willett, MD, DrPH, MPH, chairman of the Epidemiology and Nutrition at... [+]
admonished the chair of the Harvard School of Public Health’s nutrition department, Walter Willett, for promoting over-simplification of scientific results in the name of public health and engaging in unseemly behavior towards those who venture conclusions that differ to his.
Willett, who is one of the most frequently quoted academic sources on nutrition in the news media, appears to have crossed a Rubicon when he denounced Katherine Flegal, an epidemiologist at the US National Center for Health Statistics, for publishing a study that showed people who were overweight (but not obese) lived longer than those deemed normal weight. “This study is really a pile of rubbish, and no one should waste their time reading it,” he told National Public Radio.
Flegal had derived this conclusion from a meta-analysis of 97 studies covering 2.88 million people, and it had been published in the prestigious Journal of the American Medical Association (JAMA). What concerned Willett – and other public health experts, who as Nature reported, later staged a symposium to criticize it – was that it seemed to counteract the general message that people should lose weight. As the journal noted:
“Studies such as Flegal's are dangerous, Willett says, because they could confuse the public and doctors, and undermine public policies to curb rising obesity rates. ‘There is going to be some percentage of physicians who will not counsel an overweight patient because of this,’ he says. Worse, he says, these findings can be hijacked by powerful special-interest groups, such as the soft-drink and food lobbies, to influence policy-makers.”
Willett is well know for being forthright in his views; but describing Flegal’s work as a “pile of rubbish” appears to have ticked off obesity researchers and biostatisticians alike, for this isn’t the first study to arrive at such a finding – and researchers lined up to tell Nature why it was plausible: a little extra weight for those who were older or older and ill, could help rather than hurt. Moreover, Flegal herself responded with some sharp statistical criticism of Willett’s “rubbish” thesis.
There was also a spectacular irony in Willett’s complaints about Flegal’s study that will not have gone unnoticed in scientific circles, namely that Willett was the co-author of a study published last fall that generated enormous controversy when its dramatic conclusions were retracted at the last minute by the publicity team at Harvard’s teaching hospital, Brigham and Women’s. The study had been promoted to the media as showing a link between aspartame and cancer: “The truth isn’t sweet when it comes to artificial sweeteners,” said the press release. But the truth was that the statistical findings were so weak and confusing that no such claim could be supported, especially given that many systematic reviews of the evidence on aspartame had not found any such link.
At the time, Dr. Steven Nissen, chair of the Cleveland Clinic’s cardiovascular medicine department told NBC News: “Promoting a study that its own authors agree is not definite, not conclusive and not useful for the public is not in the best interests of public health.” As NBC’s Robert Bazell put it, “the situation is a great example of why the public often finds science confusing and frustrating.”
It also emerged that the study had been rejected by six journals, before being published in the American Journal of Clinical Nutrition, where Willett is a member of the editorial board. “I do think this finding is strong enough to justify further study on aspartame and cancer risk,” Willett told NPR.
In other words, findings, no matter how vague, are still good when Willett is involved in the study, even though they muddy the public health message on aspartame, which is that it is safe; but findings, even if they are stronger – as with Flegal’s – are bad when they muddy the public health message on weight gain.
This is more than merely unsporting: Such a brazen double standard is a warning that what counts as “science” in public health is a mixture of data – good, bad and middling –, methodological limitations, and interpretation. The goal – to save the public either from themselves or external threats – influences what is researched and how that research is interpreted. Given the complexities of the problems and the challenges of measurement (think about how much “evidence” is generated in nutrition from people recalling what they eat), the political need for clear conclusions and recommendations, combined with the academic need for findings to be published in scholarly journals that want positive findings, means that public health messages are often scientifically weaker than they sound. And, as Nature noted in its editorial,
The problem with simple messages and black-and-white statements is that they tend to be absolutes and so the easiest to falsify… It is easy to see why those who spend their lives trying to promote the health of others gnash their teeth when they see complex findings whittled down to a sharp point and used to puncture their message. It is more difficult, from a scientific perspective, to agree that these findings should not be published and discussed openly, warts and all, purely because they blend uncertainty into a simple mantra. Make things as simple as possible, Einstein said, but no simpler. And simple, black-and-white messages can cause confusion of their own. All things in moderation — and that should include the language we use.
Science is complex, and Willett’s message to his fellow scientists appears to be that the public can’t be trusted with this complexity (except, as noted, when it might be something that he thinks is worthy of research); the question, which the public might ask in turn, is whether Willett can be trusted with complexity given his apparent intolerance for it in other scientists?
