Psychobiological effects associated with a progressive body weight loss may help to improve the understanding of psychological barriers to weight loss. We hypothesized that a moderate body weight loss (about 10% of initial body weight) is accompanied with some negative psychological impact. Four questionnaires [SF-36 Health Survey, Three-Factor Eating Questionnaire (TFEQ), Beck Depression Inventory (BDI) and Pittsburgh Sleep Quality Index (PSQI)] were administered at each phase of a body weight loss program that consisted of a supervised diet and exercise clinical intervention to 11 obese men (mean BMI = 33.4 kg/m(2), mean age = 38 yr). The three phases investigated were: 1) at the beginning of the intervention (baseline); 2) after 5 +/- 1 kg body weight loss (Phase 1); and 3) after 10 +/- 1 kg body weight loss (Phase 2). Using the SF-36 Health Survey, physical and mental health were shown to be significantly improved at Phase 1 (p < 0.05). The TFEQ showed that cognitive dietary restraint increased (p < 0.001), and both disinhibition (p < 0.05) and susceptibility to hunger (p < 0.05) were significantly reduced at both Phase 1 and 2 compared to baseline. Depression as measured by the BDI significantly increased at Phase 2 (p < 0.05) compared to baseline and Phase 1. However, the mean BDI scores observed remained below the cut-off point for likely clinical significance. Finally, the PSQI showed that sleep quality was significantly improved at Phase 1 compared to baseline (p < 0.01). Altogether, these results suggest that a substantial improvement in the psychobiological profile occurs with a 5-kg weight loss (Phase 1) but that with additional weight loss (Phase 2) a small, but significant increase in depression occurred and seems to be associated with the increase in rigid restraint of eating. However, prospective studies with a larger sample are needed to confirm and deepen these results.