The study showed that obese people salivated longer than the non-obese in response to a new taste. Study author Dr. Dale Bond explained the implications of this result:

Saliva production tends to decline in most people once they've gotten used to the taste of a certain food and had enough of it. The process, called habituation, is associated with a feeling of fullness.

Although more research is needed, it seems that people struggling with obesity may not be receiving mental cues — the feeling of being used to a new taste, and of being full — as quickly as people who aren't obese. Thus they may keep eating longer. This result is in line with the view of Dr. David Kessler, who believes overeating is a mental problem, similar to addiction. He tells Salon's Katharine Mieszkowski:

In people who have a hard time controlling their eating, their brain circuits remain elevated and activated until all the food is gone. Then the next time you get cued, you do it again. Every time you engage in this cycle you strengthen the neural circuits. The anticipation gets strengthened. It's in part because of ambivalence. Do you ever have an internal dialogue? "Boy, that would taste great. No, I shouldn't have it. I really want that. And I shouldn't do it."

That sort of ambivalence increases the reward value of the food.

While overeating is affected by factors like the amount of fat, sugar, and salt in food, and the number of chews per bite (the fewer chews, the more we overindulge), Kessler says its true cause is what's going on in our heads. The reason diets don't work, according to him, is not that the body returns to a certain set point — it's that the brain does. He says,

Sure, I can take you out of your environment. I can give you meal replacements, or you can white-knuckle it, and for 30 days, 60 days, 90 days, resist eating a lot of food, and you can lose weight, no question about that.

Now your diet's over. I put you back into your environment. You still have that old learning, that old circuitry. What's going to happen? You're going to get bombarded with the cues again and you're going to gain it back if you have not laid down new circuitry and new learning on top of that old circuitry.

But why is this circuitry a problem now, when it wasn't forty years ago (Kessler says that in the 1960s, people's weight remained stable throughout their adult lives)? Kessler's answer isn't totally satisfying:

We're eating in a disorganized and chaotic fashion. And we're being bombarded with the cues.

We make food into entertainment. We make it into a food carnival. Go into a modern American restaurant: the colors, the TVs, the monitors, the music. You do it with your friends. We've taken sugar and added all these multiple levels of stimuli. What do we end up with? Probably one of the great public health crises of our day.

Of course, we didn't have TVs in restaurants forty years ago. But food has been part of entertainment and celebration, and eating something people do with their friends, for a very long time. Looking for a "food carnival"? Try Carnival. So while Dr. Kessler's insights — and the findings about overeating and saliva — are interesting, its doubtful they're the whole story.

Why We Can't Eat Just One [Salon]
New Study Suggests Why Obese People Overeat [Diet Blog]

In an interview with the Wall Street Journal, Jeffrey A. Trachtenberg says to Kessler (who is the former head of the FDA), "At times I couldn't decide whether you felt that the overweight were victims or undisciplined. Which is it?" Kessler replies:

The answer is probably neither. Nobody has explained to people what is going on with them, or given them the tools to cool stimuli. Yes, you are bombarded throughout the day. You respond. And that creates torment for people. But just because we are activated and stimulated doesn't mean that that there aren't things we can do. Yes, their brains are being hijacked. But once we understand what is going on, we can change.

In addition, Kessler says many people have a syndrome of "hyper-eating" — "the loss of control in the face of highly palatable foods, lack of feeling full." It's especially interesting in regards to kids:

Is it nurture or nature? You expose children who are eating fat, sugar and salt all day. They've never been hungry a day in their lives. Once you lay down that neuro-circuitry, it's there for life. The actual act of consumption isn't as strong as anticipation. It's the conditioning associated with a cue. Once you are cued and you're activated, it amplifies the reward value. It torments you. You want it more.

Businessweek notes that in Kessler's book, he documents a conversation he had with a food industry consultant:

Sugar, fat and salt make a food compelling, said the consultant. They make it indulgent. They make it high in hedonic value, which gives us pleasure. "Do you design food specifically to be highly hedonic," I asked. "Oh, absolutely," he replied without a moment's hesitation. "We try to bring as much of that into the equation as possible."

Businessweek's Cathy Arnst says we can't just blame the food industry: "As parents, we are all too guilty of stimulating our children's hedonic cravings early and often." She continues: "In the last few weeks my 10-year old daughter and I have eaten with several friends, and every time the children have been offered either mac n'cheese, hot dogs or pizza, usually accompanied by potato chips and soda and followed by ice cream. Adults too easily assume that kids won't eat anything else. My daughter actually likes healthy foods and doesn't like soda (when we got home from one dinner she asked why she couldn't have any grilled salmon). But when offered the option of fat-laden pasta or salt-infused hot dogs, guess which she chooses?"

Dr. Kessler swears that overeating is not a disease. But it is something that alters your brain chemistry: Everytime a kid eats food laden with sugar, fat and salt, it "it strengthens their neuro-circuitry to eat that food again." And we're living in a world in which we're constantly stimulated: "[Hyper-palatable foods are] available 24/7 and we've added the emotional gloss of advertising," Dr. Kessler says.

The big question is, should the government step in? Cathy Arnst says, "You would never give a child a cigarette. Or a drink, or a snort of cocaine. But everyday we American parents are giving our children something almost as addictive-meals laden with sugar, salt and fat." It's illegal to give a child a cigarette, alcohol or drugs. But even though there's a soda tax in the works in New York, do you think that the government should be regulating other junk food, especially if it is targeted to children? What if you couldn't buy McDonald's, Krispy Kremes or Hostess Cupcakes until you turned 18? (Kessler's view on that? "It's about how we as a country view the product. What was the real success of tobacco? We changed how we viewed the product. It was a critical perceptual shift. That's the key.")

The Science And Psychology Behind Overeating [WSJ]
How Mac N' Cheese Is Like A Cigarette [BusinessWeek]

Related: The End of Overeating: Taking Control Of The Insatiable American Appetite [Barnes & Noble]