Bioelectrical impedance analysis of body composition indicators in healthy young people depending on the initial somatotype

Abstract

Body mass index (BMI) remains the most common indicator of body weight assessment, but it does not take into account the ratio of fat and muscle components, the level of visceral fat and hydration of the body. This limits its informativeness for early detection of metabolic disorders, sarcopenia and hidden obesity, especially in young people with normal BMI. In this regard, the use of bioimpedance analysis (BIA) taking into account somatotype and gender is relevant. Purpose. The aim of the study was to conduct a bioelectrical impedance analysis of body composition parameters in healthy young people depending on the initial somatotype. Materials and methods. 307 practically healthy students aged 18–22 (228 girls and 79 boys) were examined. Body composition was determined by bioimpedance analysis using a TANITA MC-780 MA analyser (Japan). BMI, percentage of fat mass (BF, %), visceral fat (VF, conventional units), relative muscle mass (MM, %), skeletal muscle mass (SM, %), sarcopenic index (SI), total water content (TBW, %) and phase angle (PA) were determined. Somatotypes were classified according to the 9-level Physique Rating scale. To interpret the obtained data, we used reference values for indicators based on age and gender, as recommended by the equipment manufacturer (Tanita, Japan) and international standards for body composition assessment. Statistical processing was performed using the Minitab 21.3.1 package. To describe the data, mean values and standard deviations (M ± SD) were calculated. Results. It was found, that 37.5% of boys and 52.6% of girls have a standard somatotype, which is characterised by a balanced ratio of fat and muscle mass. Students with increased fat content (“High Fat/ Average Muscle” and “High Fat/ High Muscle” somatotypes) showed an increase in BMI, BF% and VF, especially in boys, indicating a risk of developing metabolic disorders at an early young age. At the same time, a significant proportion of students with „Average Fat/Low Muscle“ and „Low Fat/Low Muscle“ somatotypes were found to have a body mass index within the normal range, but they had a reduced ratio of muscle mass, as confirmed by a decrease in percentage of skeletal muscle, sarcopenic index and phase angle, an indicator, that is associated with impaired cell membrane integrity, muscle strength and quality. According to the European consensus EWGSOP2 (European Working Group on Sarcopenia), a sarcopenic index < 7.0 kg/m² in young men and < 5.5 kg/m² in young women is considered as sarcopenia. Our study found a critical decrease in SI in boys with the „Average Fat/Low Muscle“ and „Low Fat/Low Muscle“ somatotypes (SI = 7.0 and 6.8 kg/m2). As for young women, the signs of sarcopenia were found in girls with the same somatotypes (SI = 5.3 and 5.1 kg/m²). Conclusions. Bioelectrical impedance analysis, accounting for somatotype and gender, is an informative tool for detecting hidden imbalances in the fat-to-muscle ratio in young, practically healthy individuals. The use of BIA allows to identify sarcopenic states, reduced cellular functional activity and increased metabolic risks by the excess visceral fat which are not determined when using BMI alone. The results justify the feasibility of implementing body composition analysis into routine preventive screenings for the student population.