An individual-participant data meta-analysis of prospective studies revealed that all-cause mortality was minimal at body-mass index (BMI) of 20•0–25•0 kg/m2, and increased significantly both below and above this normal range. The analysis included 3 951 455 never-smokers (without chronic diseases at recruitment who survived 5 years, median follow-up 13•7 years) in 4 continents from 189 prospective studies, of whom 385 879 died. The primary analyses are of these deaths, and study, age, and sex adjusted hazard ratios (HRs), relative to BMI 22•5–<25•0 kg/m2. For BMI over 25•0 kg/m2, mortality increased approximately log-linearly with BMI; the HR per 5 kg/m2 units higher BMI was 1•39 in Europe, 1•29 in North America, 1•39 in East Asia, and 1•31 in Australia and New Zealand. This HR per 5 kg/m2 units higher BMI (for BMI over 25 kg/m2) was greater in younger than older people (1•52 for BMI measured at 35–49 years vs 1•21 for BMI measured at 70–89 years), greater in men than women (1•51 vs 1•30), but similar in studies with self-reported and measured BMI. The HR was 1•13 for BMI 18•5–<20•0 kg/m2; 1•51 for BMI 15•0–<18•5; 1•07 for BMI 25•0–<27•5 kg/m2 and 1•20 for BMI 27•5–<30•0 kg/m2. The HR for obesity grade 1 (BMI 30•0–<35•0 kg/m2), grade 2 (35•0–<40•0 kg/m2) and grade 3 (40•0–<60•0 kg/m2) was 1•45, 1•94, and 2•76, respectively. There was no evidence for so called ‘obesity paradox’. BMI above 25 was correlated with coronary heart disease, stroke, and respiratory disease; it was also moderately correlated with cancer. Source: http://www.thelancet.com/
一项对前瞻性研究的个体参与者数据的荟萃分析表明，体重指数20•0-25•0公斤/平方米的全因死亡率最小，低于或超过这个正常范围则死亡率均显著升高。该分析包括4大洲189个前瞻性研究中的3 951 455不吸烟者（加入时无慢性疾病，存活5年以上，中位随访13•7年），其中385 879人死亡。相对于体重指数22•5- <25•0公斤/平方米，主要分析经校正研究，年龄和性别后的死亡风险比。对于体重指数25•0公斤/平方米以上，死亡率增加与体重指数约呈对数线性关系;体重指数每增加5公斤/平方米单位的风险比为欧洲的1.39，北美的1.29，东亚的1.39及澳大利亚和新西兰的1.31。较年轻者该体重指数每增加5公斤/平方米单位的风险比（体重指数25公斤/平方米以上）较年老者更高（35-49岁测得体重指数为1•52，而 70-89岁测得体重指数为1.21），男性比女性风险更大（1•51对1•30），但在自我报告和测量体重指数研究中相似。 风险比分别为体重指数 18•5- <20•0公斤/平方米的1.13; 体重指数 15•0- <18•5公斤/平方米的1.51; 体重指数 25•0- <27•5公斤/平方米的1.07和体重指数 27•5- <30•0公斤/平方米的1.2。一级（ 体重指数30•0- <35•0千克/平方米），二级（体重指数35•0- <40•0公斤/平方米）和三级（体重指数40•0- <60•0公斤/ 平方米）肥胖的风险比分别为1•45，1•94和2•76。无任何证据支持所谓的“肥胖悖论”。体重指数超过25与冠心病，中风，和呼吸系统疾病相关;也与癌症适度相关。来源：http://www.thelancet.com/