Hormonal, lifestyle, and dietary factors in relation to leptin among elderly men

Background: Leptin, the adipocyte-secreted protein product of the ob gene, has been strongly linked to obesity and is believed to play a role in the r egulation of the reproductive system. This study examines the potential inf luence of lifestyle and dietary factors, as well as of other hormones, on s erum levels of leptin. Methods: The authors studied a population of 48 heal thy elderly Greek men. Sera from these men were analyzed for leptin, severa l steroid hormones, sex hormone-binding globulin, and insulin-like growth f actor 1. The authors also utilized data from food frequency questionnaires and information on demographic, anthropometric, and lifestyle (cigarette sm oking, alcohol and coffee drinking) factors. Results: Using linear regressi on modeling, serum leptin levels were inversely associated with testosteron e and positively associated with estradiol and dehydroepiandrosterone sulfa te, after adjustment for the other hormones and body mass index (BMI). Lept in levels in men with a BMI >30 kg/m(2) were 170% higher than in men with a BMI <27 kg/m(2) (95% CI 63-346%). Height was also positively associated wi th leptin, independent of BMI. No notable relationships were observed betwe en leptin, on the one hand, and smoking, alcohol drinking, coffee drinking, or total energy intake, on the other. When total energy intake was separat ed into its three major components (carbohydrate, fat, and protein), it app eared that fat intake may have an isocalorically differential effect on ser um leptin levels; one marginal quintile increase in fat intake corresponded to an 11% increase in leptin (95% CI 0-24%). Conclusion: Serum levels of l eptin may be influenced by other endocrine factors, especially testosterone and estradiol, and may be positively associated with excess fat intake ind ependently of obesity.