There is a researcher at The Harvard Medical School named David Ludwig who's done a terrific series of studies on the glycemic index and found how it relates to food intake, body weight regulation, and health.
They did, though, give a warm response to N-acetyl-cysteine - an amino acid supplement sold in healthfood stores, thought to work by increasing the body's ability to mop up destructive chemicals which build up in the liver as enzymes break down ethanol.
By controlling for individual and environmental influences on weight, such as income and health, they then measure whether food-price changes affect body-mass index (BMI).