COMPARISON BETWEEN DIFFERENT METHODS FOR MEASURING BODY FAT AFTER A WEIGHT LOSS PROGRAM

ABSTRACT Introduction Accurate and sensitive measurement of body composition is an important tool in the diagnosis and control of obesity. Objective To compare body fat changes measured by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), and skinfolds (SK) in healthy overweight adults in order to evaluate whether all three methods can be used during a weight loss program (WLP). Methods Eighty-four men (n=36) and women (n=48), body mass index 25–29.9 kg/m2, aged between 18-50 years, non-smokers and sedentary, were randomly assigned to strength, endurance, combined strength plus endurance, or physical activity recommendations groups. All subjects followed a hypocaloric diet (25-30% decrease in energy intake in terms of the total daily energy expenditure). The intervention lasted 22 weeks. Results The highest correlation was obtained between DXA and SK when men and women were studied together (r=0.864, p&lt;0.01). In women, significant differences were found between DXA and BIA in fat percentage (underestimation of BIA 2.4%, p&lt;0.05). The underestimation was more determinant for both fat percentage and fat mass in men, 13.2% versus 10.2%, and 6.8 kg versus 4.2 kg between BIA and SK respectively (p&lt;0.05). All the procedures obtained similar results (p&gt;0.05) when changes in body fat caused by intervention were analyzed. However, considering results of the minimal difference compared to DXA, BIA showed the greatest sensitivity to detect changes in fat percentage and fat mass, while SK underestimated the changes, with a significantly lower percentage considered real (p=0.01). Conclusion The SK method seems to underestimate real changes, therefore DXA and BIA can serve as more effective tools to measure the change in fat percentage and fat mass during WLP. Level of evidence II, Diagnosis.摘要：精准且灵敏的身体成分检测是肥胖诊断与病情管控的重要手段。本研究旨在对比双能X线吸收测定法（dual-energy X-ray absorptiometry, DXA）、生物电阻抗分析（bioelectrical impedance analysis, BIA）与皮褶厚度测量法（skinfolds, SK）对健康超重成年人体脂变化的检测结果，以评估三种方法是否均可应用于体重减轻计划（weight loss program, WLP）中。 研究方法：纳入84名受试者，其中男性36名、女性48名，体质指数为25~29.9 kg/m²，年龄18~50岁，均为非吸烟者且日常久坐不动，随机分为力量训练组、耐力训练组、力量联合耐力训练组以及遵循体力活动推荐指南组。所有受试者均遵循低热量饮食方案，即相较于每日总能量消耗，能量摄入减少25%~30%，干预周期共计22周。 研究结果：合并分析男女受试者数据时，DXA与SK的检测结果相关性最高（r=0.864，p<0.01）。女性受试者中，DXA与BIA的体脂百分比检测结果存在显著差异，BIA较DXA低估了2.4%的体脂百分比（p<0.05）。对于男性的体脂百分比与体脂质量，两种检测方法的低估差异更为显著：BIA与SK的体脂百分比低估率分别为13.2%与10.2%，体脂质量低估量分别为6.8 kg与4.2 kg（p<0.05）。分析干预所致体脂变化时，三种检测方法的结果均无显著差异（p>0.05）。但相较于DXA的检测结果，以最小差异为参照时，BIA检测体脂百分比与体脂质量变化的灵敏度最高；而SK则会低估体脂变化，其检测所得的真实变化占比显著更低（p=0.01）。 研究结论：皮褶厚度测量法似乎会低估真实的体脂变化，因此在体重减轻计划中，DXA与BIA可作为检测体脂百分比及体脂质量变化的更有效工具。证据等级：Ⅱ级，诊断类研究。