Total body nitrogen in health and disease: effects of age, weight, height, and sex.

Total body levels of nitrogen were measured by prompt-gamma neutron activation analysis in 136 healthy adults in the general population (age 20 to 80 years), in 55 cancer patients, and in 20 obese subjects. In order to evaluate the TBN values for the patients, it was necessary to normalize the data for possible differences due to body habitus. This normalization was defined as the ratio of the measured nitrogen level to a predicted nitrogen level derived from the normal population. The parameters of sex, age, Ht, Wt, and fat were used to calculate expected "normal" values of nitrogen. For the cancer patients, an average TBN deficit of less than 10% was observed. Individual patients, however, showed deviations from the TBNp value as large as 28%. For obese patients, the TBN values were normal to slightly high. When adjusted for body size, the deficit of TBN in the cancer patients was approximately half that observed for TBK.