Researchers split graduate students into two groups..."One group was given a two-digit number to remember, while the second group was given a seven-digit number. Then they were told to walk down the hall, where they were presented with two different snack options: a slice of chocolate cake or a bowl of fruit salad."
"Here's where the results get weird. The students with seven digits to remember were nearly twice as likely to choose the cake as students given two digits. The reason, according to Professor Shiv, is that those extra numbers took up valuable space in the brain — they were a "cognitive load" — making it that much harder to resist a decadent dessert. In other words, willpower is so weak, and the prefrontal cortex is so overtaxed, that all it takes is five extra bits of information before the brain starts to give in to temptation."
As it turns out, the rational part of our brain that says "GAH! Wait! Don't eat that piece of pizza! You've already had five slices!" gets distracted pretty easily. For example, if you hand it 7 digits to remember, it's too busy juggling those numbers around so the Id takes over and heads right for the chocolate cake.
Seven digits is enough to shut down the rational part of the brain that controls your impulses.
Now imagine you're on a diet that explicitly requires you to hold numbers in your head....like counting calories. Seems pretty self defeating in light of this research, eh?
This is exactly why I've started writing down what I eat as soon as possible, either on paper or somewhere online. I want to get those numbers out of my head and recorded somewhere as soon as possible.