Characteristics of fat-free mass among middle and high school adolescents in Yinchuan City

Objective To elucidate age-and sex-specific characteristics in fat-free mass (FFM) among middle and high school adolescents in Yinchuan City, China, and to provide a scientific basis for healthy development, chronic disease prevention and intervention in children and adolescents. Methods Using a convenient cluster sampling method, 1 175 middle and high school adolescents, aged 10 to 20 years old, from Yinchuan, China, were selected to participate in a questionnaire survey and physical examination, which involved body composition by bioelectrical impedance analysis (BIA). Results For adolescents aged 12 to 18 years, FFM and the fat-free mass percentage (FFMP) of boys increased with age (from 39.78 to 52.63 kg; 77.51% to 83.80%, respectively), the age trends of the FFM and FFMP of body parts were in the similar pattern, and were significantly higher than those of girls (all P<0.05). In girls, the FFM reached a peak of 40.96 kg at 15 years old, and decreased slightly between the ages of 15 and 18 years, the age trends of the FFM of body parts were in the similar pattern, and the FFMP decreased with age (from 75.63% to 71.91%). In addition, in girls, the age trends of the FFMP of left and right legs were the same as the general trend, while the FFMP of left and right arms increased with age. The FFMP of the trunk reached a minimum of 29.93% at 15 years old and increased from 15 to 18 years old (all P<0.05). Conclusion For middle and high school adolescents aged 12 to 18 years old in Yinchuan City, China, the distribution of FFM changed in accordance with age and gender differences, in accordance with the characteristics of the adolescents’ growth and development. 【摘要】 目的 了解银川市中学生瘦体重分布的年龄变化趋势和性别差异, 为儿童青少年健康发育、预防慢性疾病和制 定干预措施提供科学依据。 方法 于 2017—2019 年 9—12 月使用方便整群抽样的方法, 随机抽取银川市 1 175 名 12~18 岁中学生进行问卷调査、体格检査, 米用生物电阻抗分析法 (bioelectrical impedance analysis, BIA) 测量其体成分。 结果 男生总瘦体重 (fat free mass, FFM) 和总瘦体重率 (fat free mass percentage, FFMP) 随年龄增加而增加 (39.78 ~ 52.63 kg, 77.51%~83.80%), 身体各部分 FFM、FFMP 年龄趋势同总趋势, 且均髙于女生 ( P 值均<0.05); 女生 FFM 15 岁达峰值 40.96 kg, 15~18 岁略有下降, 身体各部分 FFM 年龄趋势同总 FFM 趋势, FFMP 随年龄增加呈下降趋势 (由 75.63% 下降至 71.91%)、左右下肢 FFMP 的年龄趋势同 FFMP, 左右上肢 FFMP 随年龄增加而增加, 躯干 FFMP 在 15 岁达最低值 29.93%, 15~18 岁上升 ( P 值均<0.05)。 结论 银川市 12~18 岁中学生瘦体重随年龄变化特点及性别差异, 符合其生长发育特征。