Studying the Effects of Sibutramine on Eating Behavior

Obesity is a major public health concern, and the search for useful pharmacologic interventions is ongoing. This study aims to develop a comprehensive series of assessments to directly assess eating behavior, cognitive functioning, and psychological functioning under sibutramine and placebo conditions.

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.

Eligibility Criteria:
Inclusion Criteria:

* moderately obese
* stable weight for a minimum of 3 months
* systolic blood pressure less than or equal to 140 mm Hg
* diastolic blood pressure less than or equal to 90 mm Hg
* pulse less than or equal to 95 beats per minute
* English language proficiency

Exclusion Criteria:

* on medications known to affect appetite, weight, or metabolism
* current or past history of: binge eating disorder, anorexia nervosa or bulimia nervosa, major depression
* current or past evidence of psychosis, bipolar illness
* current or past history of alcohol or drug abuse or dependence
* known history of learning disorder or developmental disability
* current or past attention deficit hyperactivity disorders
* low platelet count
* current diabetes mellitus
* uncontrolled asthma, or controlled only with oral steroids
* hypothyroidism not adequately treated
* pregnancy, planning to become pregnant, or lactation within the previous 6 months
* history of neurological disorder or injury
* history of moderate or severe head injury
* waist circumference greater than 188 cm
* indwelling metallic object, non-removable metal jewelery, medicinal patch or recent metallic ink tattoo
* pacemaker
* metallic implants
* medication patches
* significant claustrophobia
* color blindness