Growth hormone (GH), a hormone originating from the anterior pituitary gland, is an important regulator of metabolism and body composition. Low GH secretion is associated with features of the metabolic syndrome, in particular increased visceral body fat and decreased lean body mass. It has been shown that GH release can be promoted by ingestion of protein, in particular gelatin protein. The question remains; is the GH-promoting effect of gelatin protein also present in a population with blunted GH response, such as visceral obesity? 8 lean women (age: 23+/-3 years, BMI: 21.6+/-2.0 kg/m (2)) and 8 visceral obese women (age: 28+/-7 years, BMI: 33.8+/-5.5 kg/m (2)) were compared with regard to their 5-h GH response after oral ingestion of gelatin protein (0.6 g protein per kg bodyweight), placebo (water), or injection of growth hormone releasing hormone (GHRH) (1 mu/kg body weight), in a randomized crossover design. GH response after placebo, gelatin protein, or GHRH was higher in lean subjects than in visceral obese subjects (p<0.05). Ingestion of gelatin protein increased GH response compared with placebo in both visceral obese (182.1+/-81.6 mug/l.5 h vs. 28.4+/-29.8 mug/l.5 h) and lean (631.7+/-144.2 mug/l.5 h vs. 241.0+/-196.8 mug/l.5 h) subjects (p<0.05). GH response after ingestion of gelatin protein in visceral obese did not differ from that in lean, placebo-treated subjects (p=0.45). GH concentrations after GHRH injection correlated significantly with GH concentrations after gelatin ingestion (AUC; r=0.71, p<0.01, Peak; r=0.81, p<0.01). Further research is needed to investigate if gelatin protein is able to improve metabolic abnormalities in hyposomatotropism in the long term or to investigate the relevance of protein as diagnostic tool in hyposomatotropism.