How many times have you looked at a table of snacks or a dessert tray and said, "I just can't resist?" That could really be true. There's new science that says some of our brains could be hard-wired to overeat.

Wendy Wessler lost 150 pounds after undergoing a gastric bypass. but the weight is creeping back. and she can't understand why she can't say no to food.

"If I am upset or I am really stressed out I just think I am going to get home, and I am going to get a bag of chips," Wessler said. "I just keep telling myself I should know better. I should be stronger."

Her behavior is common to the estimated 70 million Americans who are chronic overeaters. And new research by former FDA commissioner Dr. David Kessler sheds light on exactly what might be the cause: the amygdala, the area of the brain that controls our desires.

For most of us-when we see a tempting snack like a potato chip, this area of the brain will light up with activity and send feelings of anticipation and craving, but once we start eating it shuts off.

But for the overeater, the amygdala remains activated while eating, creating that feeling of want, even after five, 10, even 50 chips.

Kessler says foods layered in sugar salt and fat trigger a powerful dopamine effect in the brain, making it particularly hard for overeaters to stop.

These four people all struggle with that compulsion.

"I call it food porn, you know, because it excites me," says Christine.

Greg Wells says he does not "eat constantly." "But when I do," he adds, "I just have a hard time stopping."

Good Morning America upped the ante and put the overeaters in a room across from their biggest food weakness.

"I want to be greedy and eat the whole bag," Wessler said, who described the emotion as a "pinball machine going off."

"There's no red light," she says. "It's like, 'Bing, bing, bing.'"

For Mary Crean, food has been a life-long compulsion.

According to her, Food "calls to you."

For Wessler, food is a constant distraction in her life.

"If there's something there edible -- I can not go about my business until I consume it," she said.

According to Dr. Kessler, Wessler "intuitively" knows what researchers have learned scientifically.

As head of the FDA, Dr. Kessler fought for nutritional details on food labels, but he's also a lifelong overeater himself. His new book "The End of Overeating" examines how food can high-jacked people's brains.

"For some of us, it could be alcohol," Dr. Kessler said. "It could be tobacco. But for many of us the most salient stimuli in our environment has become food."

Kessler and Dana Small, a neuro-scientist at Yale University, say brains scans confirm how addictive food can be. They allowed subjects to smell and then taste a chocolate milkshake. Using a functional MRI, they examined the patients' brains' reactions.

"This area of the brain should be shut off when you actually taste what you've been smelling," Small said. "And in people who are overweight or obese, the area's not being shut off. And so it's still high." 

Kessler says the food industry doesn't need brain scans to know what triggers people to eat.

"We've taken fat, sugar and salt, we've put it on every corner, we've made it available 24/7. We've made it acceptable to eat any time of day," Kessler warns. "We've made it into entertainment. It is a food carnival."

What's the answer?

According to Kessler: "One of the ways to cool down the power of that food is to look at food in a different way. We need food. Food has to be pleasurable. But I now look at huge plates of food and I say, "I don't really want that."

And that's just what Greg Wells did, one of GMA's four overeaters. He lost 135 pounds over 14 months. Now when faced with his favorite food, he is the one with power.

 Email To Friend