Absence of naloxone sensitivity in obese humans.

Studies in rodents suggest the possibility of an association between elevated endogenous opiate activity and overeating and obesity. One measure of elevated opiate activity is sensitivity to the opiate antagonist naloxone. Seven massively obese human subjects showed no subjective or physiological sensitivity to large intravenous doses of naloxone. This finding fails to support a relationship between elevated endorphin activity and human obesity.