This study explores whether the addition of aspartame-sweetened foods and beverages to a low fat, hypocaloric diet enhances compliance and resulting weight loss. Fifty-nine obese (130-225% of ideal body weight), free living men and women were randomly assigned to either a Balanced Deficit Diet (BDD) or a BDD supplemented with aspartame. Over a 12-week weight loss period, volunteers attended weekly support group meetings including behavior modification training and exercise instruction. Males achieved a clinically significant weight loss (greater than 23 lb) in both study groups, while females lost an average of 12.8 lb in the control group vs. 16.5 lb in the experimental group. In both treatment groups, sleep, general energy level, level of physical activity, and feeling of well-being showed clinically meaningful improvement. This study suggests possible advantages to supplementing a BDD with aspartame-sweetened foods as part of a multidisciplinary weight loss program. The small sample size prohibits definitive conclusions but does provide the protocol for a larger, outpatient clinical trial.