Influence of external and covert food stimuli on insulin secretion in obese and normal persons.

Exposure to food produces an increase in insulin secretion that is more pronounced in obese than in normal persons. We sought to replicate this finding as well as to determine whether insulin secretion could be influenced by thoughts about food and eating. Normal and obese subjects were presented in counterbalanced order with an external food stimulus or instructions to think about food and eating. Levels of insulin, salivary output, and hunger ratings were obtained prior to and immediately following stimulus presentation. All subjects displayed higher insulin levels following stimulus presentation, with the values for the obese higher than for normals. Although the insulin secretion of the obese was greater in response to the covert as opposed to the external stimulus, the difference was not significant. Salivary output following stimulus presentation was higher for the obese than normals, with hunger ratings increasing in both groups. These data support an expanded role of insulin as an appetite-inducing mechanism.