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To the Editor.—
I wish to comment on a recent letter by Antonio Boba, MD (235:2476, 1976) and on two recent articles on the evaluation of obesity (234:1158,1190,1975). In general practice, the use of the ponderal index (PI) is the most convenient method of setting weight standards. Dr Carl Seltzer (N Engl J Med 274:254-259, 1966) relates PI to mortality rates. He plots a curve of mortality risk that becomes asymptotic at a PI value of 12.3. He states "The ratio of actual to expected mortality does not appreciably increase beyond 100 until the ponderal index is approximately 12.3 or lower. Below that level the mortality ratio rises at all ages."Reworking the equation for ponderal index, we have derived the following formula:We have calculated a standard of weight that can be labeled "threshold weight" (TW). This is defined as the crucial weight, above which the mortality for the
Shemesh A. Threshold Weight and Ponderal Index. JAMA. 1976;236(19):2173. doi:10.1001/jama.1976.03270200013011