Pounds of Personality

It’s November, which means that Thanksgiving is rapidly approaching—and with it the season of temptation. Beginning with the giblet gravy and ending with the New Year’s Eve champagne toast, the weeks ahead will add a pound of weight to the typical American—a pound that will rarely be lost. That means steadily expanding waistlines as we move from young adulthood into middle age and beyond.

But some people won’t follow this trend. Some are conscientious and disciplined and know where to draw the line on indulging, while others seem to lack control of their impulses and desires. Some experts have even suggested that there is an obese personality type—a neurotic style of thinking and feeling and acting that leads inevitably to unhealthy weight gain.

But is it that simple? Obviously a chronic lack of discipline can lead to overindulgence and extra pounds, but psychological scientists—both aging specialists and weight specialists—are rethinking the obvious. Is it possible that the interaction between personality and weight is a two-way street—that is, that weight gain might also cause a change in personality, a shift toward impulsiveness over time?

A large team of scientists has been exploring this intriguing possibility. Headed up by Angelina Sutin of the Florida State University College of Medicine, the researchers used data from two large and ongoing studies to see if the process of gaining weight might lead people to see themselves differently—and as a result to change core personality traits. The demographically diverse samples totaled more than 1,900 subjects, including significant numbers who gained more than 10 percent of their starting body weight over a decade’s time. All were middle-aged, but one sample was older—late 50s—and well educated, while the other was younger—mid-40s—and less educated. The subjects provided accurate weight records—to start and 10 years later—and personality assessments for both points in time.

The scientists looked at a range of personality traits, but were particularly interested in those theoretically connected to overeating and weight gain: impulsivity, excitement seeking, self-discipline, and deliberation. If indeed it’s true that weight gain shapes personality—as hypothesized—then one would expect those who bulked up to become more impulsive and less deliberative—more likely to act without thinking.

But that’s not what the scientists found exactly. It was more of a mixed bag, as described in a forthcoming article in the journal Psychological Science. As expected, those who gained weight over the decade did become more impulsive—they were more likely to give into temptation. But they did not become less thoughtful. In fact, the opposite was true—they became more deliberative than they were before, and much more deliberative than those whose weight remained stable. Why would this be?

The scientists have some ideas that might illuminate these paradoxical findings. In American society today, there is a pervasive and potent stereotype of the overweight as lazy, weak-willed, lacking in discipline. It’s possible, Sutin and her colleagues believe, that as individuals gradually put on pounds, they begin to internalize this caricature—they see themselves as conforming to this personality stereotype.

That might explain the shift toward impulsivity, but what about the seemingly inconsistent increase in deliberation? Gaining 10 percent of one’s body weight is not just going up a belt size—it’s a big gain, noticeable to family and friends and colleagues. It’s quite possible, the scientists speculate, that negative feedback from these close acquaintances—an offhand comment about “second helpings”—could make those who are getting heavier stop and think about their behavior, even if they don’t actually resist the temptation. They may also spend cognitive power rationalizing a slip afterward. All this thinking adds up to a more deliberative personality—but one in a heavier body.

These findings have practical implications for those struggling with their weight. People who are neurotically impulsive cannot control their cravings, so they are more prone to overindulge and gain weight, but their weight gain in turn increases their neuroticism and impulsivity—creating a vicious downward spiral that depletes their cognitive control generally. In short, yielding to temptation today diminishes the ability to resist cravings tomorrow, and on and on, one holiday season after the next.

Excerpts from Wray Herbert’s two blogs—“We’re Only Human” and “Full Frontal Psychology”—appear regularly in The Huffington Post and in Scientific American Mind.