The management of overweight may include the use of dietary supplements targeted to counter the feeling of hunger. A randomized, double-blind, placebo-controlled trial has been performed in 20 overweight females. These subjects were randomly assigned to supplement their diet with either an extract from Griffonia Simplicifolia (10 subjects) or a placebo (10 matched subjects) for 4-weeks, in conjunction with a personalised reduced calorie diet. The main aim of this study was to evaluate the efficacy, by the assessment of 24-h urinary 5-hydroxyindoleacetic acid levels (5-HIAA), of 1-month administration of a dietary supplement containing 5-hydroxytryptophan (5-HTP) from botanical extracts in healthy, overweight females. Secondary endpoints were the assessment of sensation of appetite (by Haber score), body composition, and severity of binge eating. The supplemented group had a significant increase of 24-h urinary 5-HIAA levels (p<0.001), and a decrease in Haber score (p<0.001) while the placebo group did not show significant changes. With regard to changes in body composition, statistically significant differences between the treatment groups were found for the mean change in BMI, suprailiac skinfold thicknesses, arm circumference and hip circumference. Other parameters were found to be similar in the treated and in the placebo groups. In conclusion, this study shows that the 5-hydroxytryptophan present in the Griffonia extract, administered via spray to the oral cavity, is adequately absorbed, as confirmed by the increase in 24-h urinary 5-HIAA, and that the supplementation of the diet of overweight women with 5-hydroxytryptophan increases the feeling of satiety associated with a decrease in BMI.