Serum leptin level among non-obese students: relationship to body fat, blood pressure, serum lipids, physical activity, and eating habits]

Leptin, a product of the ob gene, is thought to play a key role in the regulation of adiposity. However, it is unclear in humans as to whether or not leptin influences the blood pressure, serum lipids, physical activity level, or eating behavior in relation to obesity. Recent reports have indicated both gender-based differences in the leptin levels and a correlation of the percentage of body fat with leptin levels has been observed among obese subjects. As far as we know, these relationships among non-obese young adults have yet to be studied. Therefore, the serum leptin concentrations among 107 non-obese students (72 males and 35 females) were measured by a radioimmunoassay(RIA). Fasting leptin levels ranging between 1.2 and 23.4 ng/mL were observed in all subjects, and the levels among females were 2.6 times higher than in males (7.64 vs 2.95 ng/mL; p < 0.001). A close correlation was observed regarding the log-transformed leptin levels with the percentage of body fat as determined by the bioelectrical impedance analysis method(r = 0.734, p < 0.001 in males and r = 0.579, p < 0.001 in females). In conclusion, these data thus suggest the serum leptin levels among non-obese students show significant gender-based differences while, in addition, the leptin levels also correlate positively with the percentage of body fat. However, it remains unclear as to whether or not the leptin levels are independently related to the blood pressure, serum lipids, physical activity level (sports activity and leisure-time activity), and eating behavior (eating breakfast, mid-day snacking and nighttime snacking).