Impact of age on associations between weight and mortality.

The effect of age on the weight associated with the lowest mortality and the effect of age on the mortality risk associated with obesity are issues fraught with methodologic complexities. Current evidence supports the notion that the body mass index associated with the lowest mortality falls within the range of 18.5 to 24.9 in men and women between the ages of 30 and 74. The impact of age on the mortality risk associated with obesity changes with age, however, and the direction of the trend depends upon the measure used.