Monday, July 1, 2013

What Fast Absorbing Carbohydrates Do To the Brain

This is David DiSalvo at Forbes

A group of overweight men were given one of two meal replacement milkshakes. The shakes were identical except that one contained high-glycemic index carbohydrates (the kind that the body digests rapidly), and the other contained low-glycemic index carbs (that take much more time to digest and absorb).

In other words, one shake was designed to fast and furiously jolt the bloodstream, while the other was a slow burner. The men were hooked up to an fMRI machine while they downed the shakes and for a four-hour period afterward.

The men who drank the high-glycemic index shakes experienced an immediate spike in blood sugar and a crash four hours later, which resulted in increased hunger, as expected.  But the critical finding is what happened in their brains after the crash — the critical window of time that sets the stage for what a person’s next meal is likely to contain.

The study found that during this period, the high-glycemic-shake participants’ nucleus accumbens—a brain area integrally associated with addictive behaviors—showed intense activation. Dopamine activity in this brain area went cuckoo for cocoa puffs. In effect, the men were experiencing a flavor of the addictive high associated with other chemicals that we already know hook us hard.  The brains of the men who drank the low-glycemic shakes didn’t show the same activation pattern.