The weight gain and ultimate adiposity in cafeteria diet-induced obesity is unrelated to the central serotoninergic tonus.

Early detection of subjects with a propensity to obesity might be of great help for setting up preventive intervention studies. In this study we tested whether the development of obesity in Wistar rats, given ad libitum cafeteria foods, could be predicted by a low prolactin (PRL) response to 5-hydroxytryptophan (5HTP), as an index of low hypothalamic serotoninergic tonus. Basal and 5HTP-stimulated (50 mg/kg body weight i.p.) PRL were measured by RIA in 15 young male Wistar rats, whose pelleted diet was afterwards supplemented with cafeteria foods. In the tested animals an increase of PRL between 4 and 56 times the basal value was observed 60 min after the 5HTP injection. After 2 months of feeding, marked inter-individual differences in weight gain between the cafeteria fed animals were observed. After 10 months of feeding, median body fat percentage, assessed by dual X-ray absorptiometry, of the overfed rats was significantly higher than that of control animals: median (range): 41.2% (28.9 - 51.5%) vs 25.1 (18.0 - 32.2%) (p < 0.0001). The PRL response at the start of the experiment was neither correlated with the monthly weight increases, nor with the fat mass percentage at the end of the experiment, suggesting that a pre-existing low hypothalamic serotoninergic tonus is probably not involved in the overeating and ultimate overweight of cafeteria diet fed animals.