Body fat at pubertal genital stage 2: a comparison between Spanish and Mexican boys

Abstract

Background/Objectives: To compare body fat mass at the same stage of pubertal maturation, genital stage 2 (G2), in a Spanish and in a Mexican sample of boys. Subjects/Methods: Data from Spain (n ¼ 177) were from a previous longitudinal clinical follow-up and data from Mexico (n ¼ 91) from a cross-sectional study. Subjects were grouped according to the presence of G2 at similar ages. Spanish sample was divided into boys with G2 at age 12 (n ¼ 60), 13 (n ¼ 74) and 14 (n ¼ 43). In Mexican sample, 23 boys were at G2 at 12 years, 38 at age 13 and 30 at 14 years. Height, weight, upper arm circumference and four skinfold thicknesses were recorded. Genital development was assessed (Tanner scale). Sum of four skinfolds (SUM), body mass index (BMI), percentage of body fat (%BF) and extremity/trunk skinfold ratio (ETR ¼ (triceps þ biceps)/(subscapular þ suprailiac)) was calculated. Results: When comparing subjects with different ages at G2 from the same country, or with the same age at G2 from different countries, no significant differences were found in adiposity variables (%BF, SUM), nor in BMI. Nevertheless, there were differences in body fat distribution: ETR was higher in Spanish boys (Po0.001), because of their greater triceps skinfold thickness (P ¼ 0.013), and due to the greater trunk fat stores in Mexican boys (Po0.01, subscapular and suprailiac skinfolds). Conclusions: There is a subcutaneous fat mass store characteristic of G2 in boys, which is not only independent of age, but is also observable in two different populations.

Sex differences in adipose development in a hunter‐gatherer population

“…Girls' continued increase in adiposity supports the demands of ovarian cycling (Ellison, 2001) and potential pregnancy (O'Sullivan, 2009; O'Sullivan et al, 2001). Boys have a short‐term increase at 11–12 years to initiate testicular development (Vizmanos et al, 2009; Vizmanos & Martí‐Henneberg, 2000), with no appreciable gains thereafter (Rolland‐Cachera et al, 1987, Wells, 2010:107), as fat stores are thought to have little direct impact on male reproductive function (Bribiescas, 2001). Thus, adipose development has been characterized by two distinct phases, hinting at separate underlying biological phases of energy mobilization and storage: (1) rebound during middle childhood (6–8 years) following brain development, and (2) a pubertal phase in preparation for reproductive maturation.…”