By Wendy Walsh

Debating the battle of the bulge is America's favorite pastime. In fact, the weight-loss industry is a cash cow simply because losing weight is so darn difficult and keeping that weight off is often harder.

Until recently, weight-loss experts have focused on behavior as the biggest factor in weight gain and obesity. The conventional wisdom is that people who have weight problems simply eat too much and move too little. But now psychologists have taken an educated look at a long-term study to ask questions about what underlying psychological forces motivate such self-destructive behavior. Could weight gain have less to do with bad habits and more to do with personality type?

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Are you prone to weight gain?
The answer is yes. Using data from an ongoing 50-year study that monitors health, researchers from the National Institute on Aging found that a number of personality traits are directly linked to those prone to weight gain. People with neurotic tendencies -- those prone to anxiety and aggression -- were likely to pack on extra pounds, as were those who enjoy taking risks. Gives new meaning to the "dangerous" dessert cart.

Another group who tended toward plump were cynical, aggressive and competitive people. Picture Wall Street power brokers shoveling in pasta at New York's Cipriani's, or riled-up tailgaters stuffing in Texas barbecue outside Reliant Stadium. Come to think of it, didn't the Grinch have a paunch too?

But the study, which compared personality to weight- and body-mass index, found that, by far, the most powerful personality trait that causes belt loosening across the lifespan is being impulsive. In fact, highly impulsive people in the study packed on an average of 22 extra pounds over the years. Can I say "duh" here? Poor impulse control is the very feature that has people overloading at buffet tables and easily distracted from a weight-loss program. The key to losing fat and maintaining a healthy body weight is consistency. Impulsive people are less likely to stick to healthy routines long enough to maintain weight in the long term.

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Does culture have anything to do with it?
Some other points about the study are interesting to note. The group of nearly 2,000 were equally divided by gender but were disproportionately white (71 percent) and highly educated (most were college educated or held graduate degrees). This leads me to consider cultural factors. Might the weight gain of whites be largely linked to psychology and the weight gain of some minorities be linked to Mom's Sunday dinners? Family dynamics and food are clearly another piece to the puzzle.

But this fascinating study begs the question: Would psychotherapy be better for sustained weight management than crash diets and sudden workout kicks? I think the answer is a resounding "yes" for those with impulse-control problems. And the side effect of therapy for this population would be improved relationships, as people with poor impulse control are also more likely to have affairs.