By David Katz, MD

According to a widely circulated op-ed in the New York Times by Paul Campos, a law professor at the University of Colorado with whom I don’t believe I have ever managed to agree on anything, our “fear” of fat — namely, epidemic obesity — is, in a word, absurd. Prof. Campos is the author of a book entitled The Obesity Myth, and has established something of a cottage industry for some time contending that the fuss we make about epidemic obesity is all some government-manufactured conspiracy theory, or a confabulation serving the interests of the weight-loss-pharmaceutical complex.

In this instance, the op-ed was reacting to a meta-analysis, published last week in JAMA, and itself the subject of extensive media attention, indicating that mortality rates go up as obesity gets severe, but that mild obesity and overweight are actually associated with lower overall mortality than so-called “healthy” weight. This study — debunked for important deficiencies by many leading scientists around the country, and with important limitations acknowledged by its own authors — was treated by Prof. Campos as if a third tablet on the summit of Mount Sinai.

We’ll get into the details of the meta-anlysis shortly, but first I’d like to say: Treating science like a ping-pong ball is what’s absurd, and what scares the hell out of me. Treating any one study as if its findings annihilate the gradual, hard-earned accumulation of evidence over decades is absurd, and scares the hell out of me. Iconoclasts who get lots of attention just by refuting the conventional wisdom, and who are occasionally and importantly right, but far more often wrong — are often rather absurd, and scare the hell out of me.

And so does the obesity epidemic.

As for the meta-analysis, a study designed to pool the results of other studies, it is in some ways complex and in some ways quite sophisticated. But in many important ways, it is very crude.

A meta-analysis is never any better than the studies it is aggregating. In this case, those studies merely looked at the population-level association between the body mass index, itself a rather crude measure of body fat — which is what really matters — and death rate.  The first, obvious limitation of this study is that it examined mortality (death) but not morbidity (illness). The Global Burden of Disease Study, recently published in The Lancet and sponsored by the World Health Organization, the World Bank, and the Bill and Melinda Gates Foundation, is widely acknowledged as one of the most comprehensive epidemiologic assessments in history. What it shows, among countries around the world, is that we are living longer, but sicker. Thanks to the cutting edge of biomedical advance, we can often forestall death; but high-tech medicine is not remotely as useful for cultivating health and vitality.

So, it’s no surprise that overweight and mild obesity do not increase mortality. They could cause an enormous burden of chronic disease and still not do so.

But why would overweight and mild obesity be associated with a lower rate of mortality, as the meta-analysis suggests? For one thing, when people get sick, they generally lose weight. The new study was in no way adjusted to exclude from the analysis people who were thin because they were sick. We have long had evidence that among older people, hanging onto weight is associated with better outcomes than losing weight.

Second, in a society where a vast majority of the whole population is either overweight or obese, who isn’t? Well, to some extent, thin and healthy people. But also, along with those who have chronic disease, there are smokers (the meta-analysis only partly corrected for this), alcoholics, people with eating disorders, people who use illicit drugs, people with severe depression, and so on. There is an enormous difference between being lean because of eating well and being physically active, and being lean because of anorexia nervosa or routine cocaine use. The meta-analysis was blind to any such distinctions.

And, lastly for now (there are more elements to this argument, but I don’t have time to write the whole manifesto right now, and you probably don’t have time to read it!), there is the fact that while overall obesity rates in the U.S. are showing signs of stabilizing, the rate of severe obesity — the very variety even this meta-analysis associates with a 30 percent or more increase in mortality risk — is “skyrocketing.”

There are two implications of this. First, it is ever less useful to ask, “How many of us are overweight?” and ever more important to start asking, “How overweight are the many of us?” And second, since as a society we are getting ever heavier, it stands to reason that those who manage to remain only overweight are, in fact, doing something right — and deriving health benefits accordingly. The danger in using the new study to renounce concerns about weight as Campos suggests is that we invite weight gain — which will take us from overweight, to mildly obese, to more severely so. Those who are overweight but stably so aren’t ignoring their health and weight; they are controlling them.

As for why those prepared to toss out everything we thought we knew about the health risks of obesity are not just wrong, but alarmingly so — let me count the reasons!

• As noted, the Global Burden of Disease report indicates that mortality is not the real menace — it’s morbidity. Obesity is consistently, powerfully associated with the risk of chronic disease.
• When I was in medical school, we learned about “adult-onset” diabetes. That is now called “Type 2” diabetes because it occurs routinely in kids as well. It occurs routinely in kids because of epidemic childhood obesity.
• The CDC is projecting that by mid-century, up to 1 in 3 Americans will be diabetic, due almost entirely to epidemic obesity. The trend is already well under way.
• For those doubting, as Prof. Campos seems to, that obesity is the cause of all this diabetes and chronic disease, there is the Diabetes Prevention Program — which demonstrates that a 7 percent loss in body weight produces a 58 percent reduction in the development of diabetes among high-risk adults.
• Studies spanning 20 years (1, 2, 3, 4) show a decisive association between healthful lifestyle practices, with resulting weight control, and a dramatic reduction in both chronic morbidity and premature mortality.
• Unlike Prof. Campos, who is a lawyer, I am a doctor — I take care of patients, including those wrestling with weight control. Over 20 years, I have seen personally the changes in health and vitality when people who are obese become lean through the application of sensible and sustainable lifestyle practices.
• My colleagues in pediatrics tell me routinely they are not only seeing Type 2 diabetes, but also fatty liver disease in overweight and obese children. When the obesity goes away, so do these ominous conditions.
• A 35 percent increase in the rate of stroke has been reported among 5-to-14-year-olds in the U.S., and the only smoking gun on the scene to account for it is epidemic childhood obesity.
• A study in roughly a million people that did control for chronic illness found a strong and consistent association between the body mass index and the risk of death, and cancer.
• The BMI is known to be a crude measure that does not account for whether weight is muscle or fat, and if fat, where on the body it resides. The evidence that excess body fat particularly around the middle is harmful is indisputable.

I guess, if Campos is right, this is all a myth. But since I actually see the evidence of it personally, as do many of my colleagues, it must be more than just a myth; it must be some kind of mass hallucination. Those, I think, are our choices. We are having a shared, population-level hallucination about the implications of epidemic obesity; or Prof. Campos is wrong. Choose.

Iconoclasts who see what the rest of the world overlooks are occasionally right. Copernicus and Galileo were right. Newton and Einstein were right. But the company is rarefied.

Most of the time, those who refute conventional wisdom profit from notoriety at our collective expense and are, in time, proven to be wrong. Immunizations are not perfectly safe, but those who have propagated conspiracy theories that are in turn spawning global resurgences of measles and pertussis aren’t doing us any favors. Atkins didn’t really help us by substituting for a narrow, obsessive fixation on dietary fat a comparably narrow, comparably obsessive preoccupation with carbohydrate.

And, here’s an example, intimately familiar to me and perhaps more vivid than the rest, about the hazards of ping-pong science. For years the party line, based on the slow accumulation of evidence, was that hormone replacement therapy at menopause would reduce chronic disease and premature mortality risk. Then, two randomized clinical trials called HERS and the WHI refuted this.

The media made hay with these “the conventional wisdom was wrong!” findings, as they tend to do. The result was that we didn’t seek a balanced truth, but went from pole-to-pole, from loving HRT to reviling it. There was baby and bathwater, but we just lumped them together and sent them down a collective drain. Women abandoned HRT in droves.

Who cares? We all should. Colleagues and I have conducted an analysis, soon to be published, demonstrating that tens of thousands of women have died prematurely as a result of this mass avoidance of judicious use of hormone replacement. It’s neither all good, nor all bad — it’s good when the right women use the right preparation at the right time in the right way for the right reasons. But what boring headlines that would make! So much more exciting to proclaim: “Everybody was wrong! There’s another conspiracy!” Much more exciting, but almost never right, and all too often lethal.

We can, of course, become unduly focused on body weight. In fact, as a culture we do so routinely. Weight is not the issue; health is the issue. It is possible to be heavier and healthy, or thinner and sick. We should keep our eyes on the prize. And the new meta-analysis may suggest that the range of “normal” for weight could be expanded, although it by no means proves it.

But at the population level, epidemic obesity is incontrovertibly established as a clear and all-but-omnipresent danger. It is absurd to suggest otherwise. And it’s those who do so, who play ping-pong with science because of misguided bias or motivated self-interest — who threaten to forestall the societal action needed to turn this toxic tide — who frighten the hell out of me!

David Katz, MD, MPH, FACPM, FACP, is the founding (1998) director of Yale University’s Prevention Research Center. This piece first appeared at The Huffington Post.