Die verband tussen leptien, liggaamsamestelling en fisieke fiksheid in swart adolessente : die PLAY-studie

Abstract

Leptin is a protein hormone primarily secreted by the subcutaneous adipose tissue and is responsible for regulating the energy balance. Individuals with more adipose tissue have much higher leptin levels and often suffer from a condition known as leptin resistance. Various factors such as gender, age, ethnicity, diet and physical activity influence the body's leptin concentration. Males have lower leptin levels than females of the same age and body fat content. Black people tend to have higher leptin concentrations than white people because of a more subcutaneous adipose tissue distribution. Physical activity serve as a main manipulator of the body's energy balance and influence leptin concentration through various adaptations associated with a more favorable body composition such as, an increase in lean tissue and a decrease in body fat. The object of this study was firstly to investigate the association between body composition - with special emphasis on adipose tissue and leptin concentration in black adolescent boys and girls of the North-West Province of South Africa. Secondly, the study aimed to determine the influence of physical fitness components and leptin concentration in the same population. In this study, 148 girls and 114 boys supplied overnight fasting blood samples. Anthropometric data: length (m), weight (kg), skin folds (mm) and circumferences of the waist (cm) and hip (cm) were measured. The percentage body fat were also measured in the BOD-POD. Finally a battery of physical fitness tests were done which included: the maximum number of sit-ups, push-ups and the bleep-test for indirect V&-max. Spearman Rank Order correlations determined that there should be adjusted for age and Tanner stage. Partial correlations were done with body composition variables, [BMI (body mass index), SSF (sum of 6 skin folds), body fat percentage], and physical fitness variables, bush-ups, sit-ups and indirect V02-max]. In both genders a strong positive relationship occurred between all the above mentioned body composition variables and leptin. In boys the strongest correlation (I= 0.8420) was found between SSF and leptin levels. In girls the strongest correlation (r = 0.7489) was found between BMI and leptin concentration. In both genders, body fat percentage indicated the lowest correlation, although it was still significant. In both genders the indirect V02-max values indicated a significant negative relationship with serum leptin concentration, although it was weak, it was the highest in boys (r = - 0314). In girls the indirect V02-max values (r = -0.235) and the maximum amount of push-ups (r = -0205) indicated significant, but weak correlations. According to the results of this study it is clear that serum leptin concentration has a strong positive relationship with body fat, more accurate, with the subcutaneous adipose tissue. It was also indicated that baseline physical fitness in these black adolescents from the selected school in Potchefstroom, North-west Province (South Africa) are statistically significant negatively correlated with leptin levels, although it was not a strong correlation.