The inverse relationship between fatness and bone mineral content is mediated by the adolescent appendicular skeletal muscle mass index: The Cogni-Action Project

Abstract

BackgroundExcess adipose tissue negatively influences bone health during childhood, affecting future bone fragility diseases such as osteoporosis. However, little is known about how adolescent appendicular skeletal muscle mass index (ASMI) may mediate the relation between fatness and bone mineral content (BMC).MethodsThe sample comprised 1,296 adolescents (50% girls) aged 10–14. A principal component analysis was performed to obtain a factor made up of four fatness indicators (a) neck circumference, (b) kilograms of fat, (c) visceral fat area, and (d) waist-to-height ratio. BMC, kilograms of fat, visceral fat area, and appendicular skeletal muscle mass were obtained by a multi-frequency bioelectrical impedance analyzer. ASMI was calculated as the appendicular skeletal muscle mass divided by height squared (kg/m2). A mediation analysis was performed adjusting by age, sex, maturation, socioeconomic status, physical activity, and adolescents' body weight. We also explore differences by sex and nutritional status.ResultsThe fatness factor explained 71.5% of the proportion variance. Fatness was inversely associated with the ASMI and BMC, while the ASMI was positively related to BMC. Overall, the inverse relationship between fatness and BMC was partially mediated by the adolescents' ASMI (29.7%, indirect effect: B= −0.048, 95%CI −0.077 to −0.022), being higher in girls than in boys (32.9 vs. 29.2%). Besides, the mediation effect was higher in adolescents with normal body weight than with overweight-obese (37.6 vs 23.9%, respectively).ConclusionsThis finding highlighted the relevance of promoting healthy habits to reduce fatness and improve muscle mass in adolescents. Moreover, this highlights the central role of ASMI mediating the inverse association between fatness and BMC in female and male adolescents. Public health strategies should promote bone health in childhood, reducing the incidence of early osteopenia and osteoporosis.

Examining the mediating role of muscle quantity in adolescents: associations with adiposity, cardiorespiratory fitness, muscular fitness, and cardiometabolic risk factors

“…These studies suggest that both low muscle mass and low muscle strength are contributors to metabolic dysfunction in the pediatric population 25 , as well as early onset of hypertensive measures 26 . Recent evidence focuses on reduction in muscle mass and cardiometabolic changes 16 , 23 , as well as understanding the mediating role of muscle quantity in the relationship between adiposity and bone mineral content 27 . Furthermore, although the interaction between reduced muscle mass and associated morbidities have not been investigated in detail in children and adolescents, excess fat with low muscle mass probably arises in childhood, reducing mobility and agility in children and adolescents 12 , and consequently compromising motor competence in adolescents with obesity 11 and metabolic health before adulthood 57 .…”

“…Therefore, the vicious cycle of reduced muscle mass and increased adiposity contribute to lower relative muscle mass also in adolescents, which can potentiate the inadequate metabolic profile 25 , as well as the early onset of hypertensive measures 26 . Recent studies focus on reduction in muscle quantity and cardiometabolic alterations 16 , 23 , as well as understanding the mediating role of muscle quantity in relation between adiposity and bone mineral content 27 . However, there is a scientific gap on the mediating role of muscle quantity, according to adiposity, components of physical fitness and the presence of cardiometabolic factors in this age group.…”

Showcasing the Chilean Cogni-Action Project: Connections between physical, cognitive and socioeconomic factors in a large sample of schoolchildren

“…(ix) How muscular fitness can mitigate the impact of fatness on bone health. This, the most recently published Cogni-Action study by Cristi-Montero et al (2022), focused specifically on physical health-related variables in the school context 48 . It examined the relationship between four different measures of adiposity, bone mineral content and appendicular skeletal muscle mass index.…”