Obesity and mortality: are the risks declining? Evidence from multiple prospective studies in the United States

Summary We evaluated whether the obesity‐associated years of life lost ( YLL ) have decreased over calendar time. We implemented a meta‐analysis including only studies with two or more serial body mass index ( BMI ) assessments at different calendar years. For each BMI category (normal weight: BMI 18.5 to <25 [reference]; overweight: BMI 25 to <30; grade 1 obesity: BMI 30 to <35; and grade 2–3 obesity: BMI  ≥ 35), we estimated the YLL change between 1970 and 1990. Because of low sample sizes for African–American, results are reported on Caucasian. Among men aged ≤60 years YLL for grade 1 obesity increased by 0.72 years ( P  < 0.001) and by 1.02 years ( P  = 0.01) for grade 2–3 obesity. For men aged >60, YLL for grade 1 obesity decreased by 1.02 years ( P  < 0.001) and increased by 0.63 years for grade 2–3 obesity ( P  = 0.63). Among women aged ≤60, YLL for grade 1 obesity decreased by 4.21 years ( P  < 0.001) and by 4.97 years ( P  < 0.001) for grade 2–3 obesity. In women aged >60, YLL for grade 1 obesity decreased by 3.98 years ( P  < 0.001) and by 2.64 years ( P  = 0.001) for grade 2–3 obesity. Grade 1 obesity's association with decreased longevity has reduced for older Caucasian men. For Caucasian women, there is evidence of a decline in the obesity YLL association across all ages.