Sex differences in the prevalence of obesity in rural African adolescents

Abstract

OBJECTIVE: To investigate the prevalence and gender differences in obesity in rural African adolescents. DESIGN: Cross-sectional analysis of a mixed-longitudinal study. SUBJECTS: Four hundred and forty-seven rural African adolescents (190 females; 257 males) aged 7.0–18.9 y. MEASUREMENTS: Anthropometric measurements of height, weight, and skinfolds at the bicep (BCP), tricep (TRCP), subscapular (SSCP) and suprailiac (SPIL) sites and derived ratios of fat distribution including trunk:limb ratios (SSTB=(SSCP+SPIL)/(TRCP+BCP) and ST=SSCP/TRCP), and the upper:lower truncal ratio (TRUNK=SSCP/SPIL). Obesity was defined as (1) a BMI greater than the NHANES III 85% centile or (2) the sum of TRCP and SSCP skinfolds greater than the NHANES III 85% centile. RESULTS: Skinfold measures were significantly greater in females throughout the age range but remarkably greater divergence was apparent after mean menarcheal age of 14.03 y (s.d.=1.25). Centralization of body fat was consistently greater in males but only significantly so after 14 y of age for the ST ratio. Obesity, defined by BMI or sum of skinfolds, was greatest in females following menarche reaching a maximum of 16.7% by BMI and 11.1% by sum of skinfolds, and almost non-existent in males. CONCLUSIONS: Increased prevalence of obesity in African females did not occur throughout adolescence but was linked to the timing of menarche. Increased fatness and obesity appears to be a post-menarcheal phenomenon probably caused by the hormonal changes leading to and following first menstruation.