The possible relationship between body weight, food preferences, and plasma neurotransmitters was investigated in 96 healthy volunteers. The volunteers were divided into groups according to sex, body mass index, and food preferences. In all groups fasting platelet-poor plasma (PPP) norepinephrine and serotonin (5-HT) were examined. PPP-5-HT was low in obese individuals (mean +/- SD: 51.7 +/- 34.6 nmol/L) in comparison with lean individuals (94.31 +/- 85.2 nmol/L; P < 0.01), in lean male carbohydrate cravers (22.7 +/- 16.4 nmol/L) in comparison with protein cravers (132.9 +/- 80.6 nmol/L; P < 0.005) and noncravers (64.7 +/- 51.7 nmol/L; P < 0.05), and in obese male carbohydrate cravers (34 +/- 22.7 nmol/L) in comparison with obese male protein cravers (98.8 +/- 28.4 nmol/L; P < 0.001). In conclusion, PPP-5-HT might be seen as a peripheral indicator of processes linked with food consumption and food preferences.