Up to now, the familiar bad guys have been hauled out to explain the fattening of America. Doctors cite not enough exercise and too much junk food, bad genes and stress. A recent study by the Rand Corporation found a new potential culprit: Kids get fat when the neighborhood price of fruits and vegetables is too high. This establishes the first connection between food cost and waistline size and opens the way for a raft of new interventions. Yet none of these explanations can account for the extent or gravity of fatness. Once a comic opportunity (Jackie Gleason, John Candy, Roseanne), obesity has become a public-health crisis—the Centers for Disease Control and Prevention describes it as an "epidemic." That makes identifying its causes more urgent.
May I make a modest suggestion: The blame may lie with that No. 1 public-health villain, the odious cigarette. Not because smoking makes people fat, but because not smoking does—or at least, stopping once you've started.
For decades, public-health officials and doctors have been publicizing the dire health consequences of cigarette smoking in an attempt to unhook the American public. Their efforts qualify as the most important public-health initiative of the last century. Yet perversely enough, evidence suggests that the rush to stamp out cigarette smoking has brought health problems along with clean lungs and wide-open arteries. Cigarettes are the best legal drug available for weight control. They're better than fen-phen was, better than Olestra hoped to be, and better than all the appetite suppressants peddled for decades under the table and above it. Ask the professionals who are paid to look underfed—fashion models and ballet dancers—what their secret is. It's unanimous (at least among legal drugs): They light up.
How good is the evidence linking smoking cessation to weight gain? In 1991, the CDC published an article titled "Smoking Cessation and Severity of Weight Gain" in the New England Journal of Medicine. The researchers used data from a national health survey and concluded that "major weight gain is strongly related to smoking cessation, but occurs only in a minority of those who stop smoking." About 10 percent of men and women were found to have experienced "major" weight gain (at least 30 pounds).
That surely isn't enough to power an epidemic. But hidden in the tables, where the most interesting data always lurk, is a more disturbing fact: In the subgroup of former smokers who had stopped for longer than one year (the real quitters), more than 22 percent had gained at least 17 pounds. That's more than a spare tire. It's enough to push former smokers across the body mass index chart toward official obesity.
For several years, few investigators followed up on these findings, perhaps for fear that pointing out the connection between quitting smoking and gaining weight might be viewed as pro-cigarette. Then this spring, a large study from Europe looked at the net effect on lung function of stopping smoking (good) and concomitant weight gain (bad). The authors concluded that, alas, weight gain was almost as deleterious to the lungs as smoking cessation was beneficial. It's hard to breathe with a weighted-down chest.
To be sure, the final statistical analysis (of various technical measures of breathing capacity) showed that lungs are better off without cigarette smoke, despite the weight gain. And the study didn't take into account other smoking-related problems, such as atherosclerosis and lung cancer, that might have further tipped the cost-benefit scales toward the quitters.
Still, the study served to remind us that smoking cessation is not an unadulterated victory for public health. Over the last two decades, the proportion of smoking adults in the United States has declined from 32 percent to 22 percent. (Right now, there are 45 million smokers and an equal number who have quit.) Meanwhile, during the same period of time, the prevalence of adult obesity—figure at least 25 extra pounds on a normal frame—has risen: from 15 percent (1976 to 1980) to 23 percent (1988 to 1994) to 30.5 percent (1999 to 2002). We can't know for sure whether these two trends are linked by anything beyond coincidence, and it's worth noting that the rise in obesity correlates with the aging of the baby-boomer population. But a causal relationship certainly is biologically plausible.
Is smoking a temporary crutch for people who would be otherwise fated to be overweight, so that when they stop smoking, they simply realize their BMI manifest destiny? This too is difficult to know. In a 1995 article, researchers looked at weight gained across a 10-year span among three groups: never-smokers, current smokers, and quitters. Current smokers were easily the thinnest group. They are followed by the never-smokers. The quitters, on the other hand, were more than twice as likely to have become overweight than the never-smokers—and far worse off, weight-wise, than those who continued to smoke.
If the choice is between smoking and obesity, which is worse for public health? For now, smoking wins hands down. Cigarettes kill about 400,000 people annually and cost $150 billion a year—half in medical costs and half in lost productivity. In contrast, medical expenditures that can be attributed to obesity were estimated at $75 billion in 2003. But obesity may not be cheaper for long. A recent study of more than 4,000 white adults followed for 30 years found that nine out of 10 men and seven of 10 women became overweight by the time they turned 60. The Rand Corporation predicts that in the year 2020 (when all the baby boomers will be mighty old), health-care costs for obesity-related conditions will rise to account for 20 percent of the total amount Americans spend on health care. The projected increase in obesity would offset decreases in the rates of other chronic conditions, resulting in a net increase in the overall disability rate.