Date of Submission


Degree Type


Degree Name

Doctor of Psychology (PsyD)



Department Chair

Robert A. DiTomasso, Ph.D., ABPP

First Advisor

Robert A. DiTomasso, Ph.D., ABPP, Chairperson

Second Advisor

Stacey Cahn, Ph.D.

Third Advisor

Thomas A. Wadden, Ph.D.


This archival-data study assessed the potentially complementary mechanisms of action of sibutramine and behavior therapy (also known as lifestyle modification) believed to be responsible for the greater weight loss observed with combining the two approaches than with either approach alone. One hundred and seventy-one subjects were randomly assigned to receive 15 mg of sibutramine per day alone, delivered by a primary-care provider in five brief office visits; behavior therapy alone, delivered by a psychologist in

18 group sessions; and sibutramine (15 mg/day) plus 18 group sessions of behavior therapy (i.e., combined therapy). Mixed effects linear model analysis was used to compare changes in scores among the groups on the Eating Behavior Inventory and on visual analogue scales of appetite. Most of the findings were either significant or in the expected direction. Subjects who received sibutramine alone and behavior therapy alone displayed improvements principally in appetite control and eating behavior, respectively.

By comparison, those who received combined therapy displayed improvements in both areas. These results provide evidence that sibutramine and behavior therapy work additively to produce greater weight loss than either therapy alone. Furthermore, they underscore the importance of prescribing weight loss medications in combination with lifestyle modification, an approach that may be facilitated through the integration of behavioral-health providers within primary care.