Effects of 5-Hydroxytryptophan on Eating Behavior and Adherence to Dietary Prescriptions in Obese Adult Subjects

Changes in plasma amino acid levels by affecting the availability of neurotransmitter amino acid precursors within the brain may influence eating behavior (Wurtman et al., 1981; Fernstrom, 1983). Among the different neuro-transmitter systems, a number of theoretical and experimental data support the role played by serotonin in the regulation of eating habits (Lytle, 1977; Li et al., 1983). Rather recently, R.J. Wurtman et al. (1981) have shown that the serotonergic system plays an important role also in the selection of macronutrients, especially in obese people consuming preferentially carbohydrate-rich foods. Moreover, a “normalization” of such aberrant behavior was obtained by pharmacologically enhancing brain serotonin synthesis (J.J. Wurtman et al., 1981). A significant reduction in food intake has been reported by Blundell and Leshem (1975) in hyperphagic obese rats by administration of tion of 5-hydroxytryptophan (5-HTP). Previous experiences from this laboratory in a group of obese adult female subjects have shown that the oral administration of 5-HTP caused the onset of typical anorexia-related symptoms, decreased food intake and promoted weight loss in the absence of any dietary restriction (Ceci et al., 1989). The aim of the present study was to confirm these data in a longer study period and to verify whether the adherence to dietary prescriptions could be improved by oral administration of 5-HTP.