Studying the Effects of Sibutramine on Eating Behavior

We will recruit 48 moderately obese men and women seeking weight-loss treatment to participate in a 3-week, randomized, double-blind, cross-over trial of sibutramine 15mg or placebo daily. At the end of weeks 1 and 3, subjects will be asked to participate in a two-day/three-night stay in the Residential Laboratory or Biological Studies Unit of the New York State Psychiatric Institute for comprehensive assessments. The major outcome variable will be the difference in total daily caloric intake between sibutramine and placebo. Assessments will concentrate on three main components of eating behavior: eating patterns, psychological processing, and neurocognitive function. Eating behavior studies will examine objective variables such as meal size, meal frequency, and subjective aspects of eating such as hunger and fullness. Psychological studies will measure hedonics, including craving, behavioral restraint, and impulsivity. Neurocognitive function assessment will gather information about decision-making, such as the effects of distractors (food and non-food) on task performance. Additionally, drawing from the field of behavioral neuroeconomics, tasks that assess decision-making and the influence of irrational factors on decisions will be assessed. Neuroimaging (fMRI) procedures will also be conducted, and will augment the psychological and neurocognitive assessments by providing a window into the underlying neural circuitry involved. Following the double-blind phase, participants will be offered open treatment with sibutramine for weight loss.