01/22/2009 05:12 am ET | Updated Nov 17, 2011

Shopping and Overeating

Sharon Begley -- who's fast becoming the best science reporter in America -- has a theory about why we pay with credit cards. Her theory also explains a lot about why we overeat.

Here's the deal. The Nordstrom lady wraps up your Jimmy Choos. If you pay with a credit card, you walk away with something tangible that makes you feel good. If you pay by cash, you still get the shoes, but you also have a specific, tangible negative experience: less cash in your billfold. That causes an area of your brain called the insula -- which is in charge of paying attention to negative feelings -- to light up like a pinball machine. When you pay by credit card, the insula snoozes.

Bottom line: paying with plastic doesn't "hurt". Paying with cash does.

To balance the Scrooge-like insula, we have a little brain structure called the amygdala which hoots and hollers like a NASCAR fan anytime there's an anticipation of pleasure. (Addiction specialists spend a lot of time talking about the amygdala -- you can see it light up like the Rockerfeller Center Christmas tree on a brain scan of any addict presented with a picture of an eight ball of coke.) The amygdala is happy when you leave Neiman's with that new Gucci outfit regardless of how you paid for it, but when you pay with cash you've got the buzz-kllling insula to contend with as well. It's like having your mom in the room back in college when you were about to light up the bong.

So what does this tell us about overeating?

A lot.

The biggest challenge in dealing with weight is the fact that there are no immediate consequences to overindulging. You've got the amygdala firing away as you eye the endless cheesecake at the buffet, but since there's no immediate negative consequence (like a lighter wallet) the insula sleeps through the food orgy.

If there were a way to immediately link the immediate pleasure of downing that pint of Cherry Garcia with the almost certain but distant pain of feeling like a lard ass, we'd be stepping away from the buffet table a lot faster than we do now.

So scientists, listen up. Figure out a way to get the amygdala and the insula to speak to each other when we're downing a 4000 calorie meal.

If it can stop us from impulse buying a Phillipe Patek, it should be able to work at the Cheesecake Factory.