In the mood for (over) eating - Go ahead, eat that pie. But the rest of the year, beware: If emotions drive your appetite, you may pack on pounds.

This Thursday, many of us will scarf down second (even third) helpings of all of the above and more -- then top it off with a slice or two of pie.

It's as plain as the crumbs on our faces: We don't always eat because we're hungry.

We eat because it's Thanksgiving and by golly, we're supposed to. We eat because we're missing Grandma or because we're irritated with Uncle Fred. "Often, people eat in response to emotional, cognitive or social cues, in response to things that are not hunger," says Heather Niemeier, professor of psychiatry at Brown University Medical School in Providence, R.I.

Just how many pounds we pack on (or keep off or fail to lose) may depend on what type of cues, other than hunger, get us eating, according to new research.

Overeating for emotional reasons can derail a diet, the research shows -- while overloading at parties (or big turkey meals) may not.

In a study published in the October issue of the journal Obesity, a team of researchers led by Niemeier separated nonhunger eating cues into two categories: eating for "internal" reasons -- for example, how we're feeling, what we're thinking -- and eating for "external" reasons -- such as where we are, who we're with and how good the food tastes.

As they expected, the researchers found that a tendency to eat for internal reasons was associated with dieters not losing weight and with previously successful dieters gaining some weight back. But they were surprised to see that a tendency to eat for external reasons was not linked.

The finding is significant, because it suggests a weakness in many weight-loss programs, Niemeier says -- namely, not focusing enough on ways to avoid emotional eating.

"We need to pay more attention to these internal triggers for unhealthy eating," Niemeier says.

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Connecting the dots

Our reasons for eating can be complicated, and we may not even be aware of all of them ourselves. To try to disentangle the reasons a bit, Niemeier's team at the Weight Control & Diabetes Research Center at the Miriam Hospital in Providence looked at two groups: people who were currently overweight and people who had been overweight at some time in the past.