广州市中老年人体脂率与常规肥胖指标相关性及其对应值的研究

Correlation between body fat percentage and general obesity indexes in middle aged and old people in Guangzhou

目的 探讨广州市中老年人体脂率（BFP）与BMI、腰围（WC）和腰臀比（WHR）等常规肥胖指标的相关性，并推算BFP相应切点值。方法 基于“广州生物库队列研究”（GBCS）平台，选择3 490名50岁及以上相对健康者随机分成两组，一组用于曲线拟合分析，确定BFP与BMI、WC和WHR间的相关方程，然后再引入性别、年龄、体力运动、吸烟、饮酒等因素进行逐步回归分析，建立预测方程，进而推算反映肥胖程度的BMI、WC、WHR各切点值对应的BFP切点值，然后与另一组进行验证。结果 BFP随BMI、WC和WHR的增加而增加，与WC、WHR相比，BMI能更好预测BFP，其回归方程为BFP=（-23.47-8.87×性别）＋2.94×（BMI）-0.024×（BMI）2，决定系数R2=0.805。根据回归方程，超重（24 kg/m2≤BMI 〈 28 kg/m2）对应的BFP分别男性为24.3%≤BFP 〈 31.1%，女性为33.2%≤BFP 〈 40.0%。与WC、WHR对应的BFP判定肥胖的一致性相比，BMI所对应的BFP判定肥胖的一致性较好，其ROC曲线下面积最大，男性为0.909，女性为0.919，灵敏度和特异度分别男性为70.3%、85.5%；女性为75.2%、93.0%。结论 BFP与BMI的相关性较好。广州市中老年人BFP对应于超重/肥胖（BMI≥24 kg/m2）的切点值男性为24.0%，女性为33.0%。

Objective To examine the correlation between body fat percentage （BFP） and general obesity indexes, including body mass index （BMI）, waist circumference （WC） and waist to hip ratio （WHR） and calculate the corresponding BFP cutoff values in the middle aged and old people in Guangzhou. The corresponding cut-point of optimal body fat percentage for Guangzhou older population. Methods Based on the Guangzhou Biobank Cohort Study （GBCS）, 3 490 relatively healthy Guangzhou residents aged ≥50 years were selected and were randomly divided into 2 groups. The equations between BFP and BMI, WC, WHR were set up with Curve fitting analysis in one group. The multiple regression analysis was undertaken to establish predictive equations between BFP and BMI, WC, WHR with stepwise model for adding gender, age, physical activity, drinking and smoking. Then, the optimal cut-points of BFP corresponding to BMI, WC and WHR to reflect the degree of obesity were calculated. The equations were then validated with another group. Results BFP increased with the increase of WHR, WC and BMI. BMI was a better predictor of body fat percentage than WC and WHR. The final regression equation was BFP=（-23.47-8.87×sex）＋2.94×（BMI）-0.024×（BMI）2,the coefficient of determination was 0.805. Based on the equation, the BFP corresponding to overweight/obesity （24 kg/m2 ≤ BMI 〈 28 kg/m2） were 24.3% ≤ BFP 〈 31.1% in men and 33.2% ≤ BFP 〈 40.0% in women, respectively. BMI had a better consistency with BFP in identify obesity compared with WC and WHR, obtained the area of ROC 0.909 in men and 0.919 in women respectively. The sensitivity and specificity were 70.3% and 85.5% in men; and 75.2% and 93.0% in women respectively. Conclusion BFP has a better correlation with BMI. The study results indicated that BFP for middle aged and old males and females in Guangzhou corresponding to overweight/obesity （BMI≥24 kg/m2） were 〈 24.0% and 〈 33.0% respectively.