The media headlines attached to the major medical news story of the past week might have been: “Shocking but true: Nearly 1 in 10 US children under the age of 5 is obese!” Had that been the headline, it would indeed have been every bit as true as it is shocking. And the really shocking part is: that’s the good news! Hold that thought, please.
Some years ago, at the prompting of Dr. Debbie Kennedy who worked in my lab at the time, I established my non-profit organization, Turn the Tide Foundation. As the name implies, our mission was, and is, to contribute all we can to efforts to contain, and reverse the ever-worsening trends in obesity and related chronic diseases in adults and children alike. Over the years since, we have developed, tested and disseminated a number of helpful programs free of charge, some of which now have considerable traction all around the world.
The name I chose for the foundation is closely related to how I view the origins of the obesity and chronic disease pandemics we are pledged to combat. Rather than seeing obesity as a disease, which implies something wrong with the bodies it affects, I see it as much like drowning — the consequence of bodies interacting with an environment for which they are ill suited. That environment may be likened to a flood of highly processed, hyper-palatable, energy-dense, nutrient-dilute, glow-in-the-dark, betcha’-can’t-eat-just-one kind of foods; an endless flow of marketing dollars encouraging us and our children to eat the very foods that propel us toward obesity and chronic disease; wave after waver of technological advance making invention the mother of necessity, and giving us gadgets and gizmos that do all of the things muscles used to do at work and at play. Our problem, at its origins, is a vast, obesigenic flood.
With that metaphor reflecting my view of the problem, it naturally invites another as the corresponding solution: a levee. When you want to contain and reverse menacing floodwaters, you build something like a levee. In doing so, you know that no one sandbag, however “good,” will do what the whole levee can do. It will take a whole lot of sandbags to top the height of the floodwaters, and turn the tide. Similarly, no one thing will fix the scourges of modern epidemiology; it will take all the right programs in all the right settings to put opportunities for health reliably and accessibly back on dry ground.
Which brings us back to the headlines. The headline we did get, in no less august a source than the New York Times, was: “Obesity Rate for Young Children Plummets 43 Percent in a Decade.” This, and similarly effusive headlines reverberating throughout the news media, would seem to invite the question: have we, in fact, turned the tide? Is the mission accomplished?
A good place to start generating an answer is, obviously, the headline-spawning study itself, conducted by scientists at the CDC, and reported in JAMA. The first reality check is the study conclusion in the authors’ own words: “Overall, there have been no significant changes in obesity prevalence in youth or adults between 2003-2004 and 2011-2012.” My friend and colleague, Dr. David Allison at the University of Alabama, publishes a weekly overview of important studies related to obesity, including a feature on discrepancies between what headlines say, and what the corresponding studies actually say. This one topped that list.
What the investigators actually reported, tracking data over a decade, is, as noted, no overall change in the population rate of obesity. In the survey sample of just over nine thousand people, representing the population of 300 million, obesity rates were stable in most age groups, including infants under the age of 2. Rates rose significantly in women over age 60, and fell significantly — although barely so — in children between the ages of 2 and 5.
That, then, was the tale that shook the dog this week: in 871 children between the ages of 2 and 5, obesity prevalence declined while it remained steady or rose in all other age groups, including children younger still.
Even so, a decline of 43 percent as reported in the New York Times and elsewhere still seems pretty impressive. But what does 43 percent mean?
You might think it means something like: obesity rates were 60 percent and are now 17 percent. If so, you would be wrong. The 43 percent reported is not an absolute percentage; it’s a relative percentage. I’ll explain the difference.
Imagine a population of exactly 100 children, ages 2 to 5; and imagine that, indeed, 60 of them are obese. Compare this group to another group the same age a decade later in which only 17 of the kids are obese. The absolute difference in the obesity prevalence here would be 43 percent.
Now, imagine instead that in the original group a decade ago, about 15 of the kids were obese, and currently, in a comparable group, about 9 of the kids are obese. The absolute decline in obesity prevalence is obviously only 6 percent (i.e., 15 percent to 9 percent). But what about the relative decline in obesity? That would be 40 percent. The formula for it is [(15 percent to 9 percent) / 15 percent] = 40 percent. The 6 percent decline is 40 percent of the baseline number. That’s the difference between absolute and relative percentages. Absolute percentages are out of 100, which is what most of us expect. Relative percentages are out of the starting number, whatever that happens to be. On a relative scale, a drop from 2 people per hundred having X to 1 person per hundred having X is not 1 percent — it’s 50 percent. Relative percentages are often reported in the medical literature, and routinely reported in the popular press, for the most obvious of reasons: they tend to sound a whole lot more dramatic than the much smaller, absolute numbers.
What were the actual, absolute numbers in this case? Obesity rates in the 2 to 5 age group fell from 13.9 percent to 8.4 percent, an absolute difference of 5.5 percent. I trust you can see why the relative change made the headlines. An announcement that “overall obesity rates are unchanged over the past decade, with some increases seen, and a possibly encouraging decline of roughly 5.5 percent in children 2 to 5” is accurate, and about as dull as dishwater. It does not well suit the media mantra: afflict the comfortable, comfort the afflicted. We have long been afflicted with bad news about the obesity epidemic; it was, apparently, time for a 43 percent dose of comfort.
In setting the record straight, I don’t want to go too far. A whole lot of attention has been directed at the problem of childhood obesity over the past decade, including the signature efforts of the First Lady. We recently saw study data indicating that obesity by age 5 is a potent predictor of lifelong weight struggles to follow, implying the converse: weight control prior to age 5 could confer lifelong benefit. That being the case, any decline in obesity prevalence in this age group is of particular importance.
So, the new study offers some potentially quite encouraging and important news. But I say “potentially” advisedly.
First, as noted at the start, the “good” news here is that nearly 1 in 10 of our kids under age 5 is obese. That such a statistic is cause for celebration says more about how bad we let things get, than about how good they are.
Second, looking at the detailed data tables in the article, I see that obesity rates did not fall steadily over the past decade in 2 to 5 years olds. They fell, then rose, then fell again. This suggests we may not yet have a reliable trend established — and the most recent numbers are just part of a fluctuating baseline. More time will tell. I am also concerned that the prevalence of excess weight for length among infants and toddlers under age 2 has not trended down. It, too, has bopped around, and overall is statistically unchanged over the past decade. This, of course, is the next cohort of 2 to 5 years old, so if their propensity for obesity is not falling, it is a portent of bad things to come. To see real promise in this study, as we all would like to do, requires an embrace of optimism, and a glass half full firmly grasped.
Which brings us back to the big question: have we turned the tide?
No. We should all recall that floodwaters crest not when the snow stops melting and precipitation stops falling, but quite some time after. Globally, the tempest of obesity in adults and children alike continues unabated — with both the prevalence, and price in human and monetary terms rising for as far ahead as we can see.
Here in the U.S., we are, at best, still producing a sizable cohort of obese 5-year-olds despite our considerable efforts, and the even larger cohort of obese 5-year-olds from several years back is just now entering the age of risk for serious metabolic complications. Here, too, the most severe consequences of rampant childhood obesity are yet to come. Here, too, the floodwaters have yet to crest. The lack of change in children under age 2 looks a bit to me like storm clouds on the horizon.
And so it is we must remain committed to stacking sandbags, and raising the levee, for the foreseeable future. We should, if anything, redouble those efforts.
But as long as we do continue to raise the levee against the advent of a crest still to come, we might also indulge ourselves in raising a glass half full in celebratory toast — and in lowering our umbrellas. No, the tide has not yet turned, but maybe — just maybe — the rain has at last stopped falling.
David L. Katz is the founding director, Yale-Griffin Prevention Research Center. He is the author of Disease-Proof: The Remarkable Truth About What Makes Us Well.