214 A BIOMETRIC STUDY OF BASAL METABOLISM IN MAN. 



We now apply a further test of the existence of a sexual differentia- 

 tion with respect to metabolic activity in the human adult. In Chapter 

 VI the value of multiple-regression equations, involving both stature 

 and body-weight, for purposes of prediction has been conclusively 

 demonstrated. We may now make use of equations of this type for 

 predicting the amount of heat in calories per 24 hours which a woman 

 would produce if she were a man of the same stature and body-weight. 

 We shall thus avail ourselves of all the advantages of the selected-group 

 method employed in earlier papers from the Nutrition Laboratory, 14 

 but by the use of suitable statistical methods shall avoid certain real 

 difficulties encountered, but not overcome, by them. 



What we have done is in effect this : We have expressed the rela- 

 tionship between heat-production and stature and weight in men as 

 a mathematical plane, the coordinates of which give the most probable 

 heat-production in individuals of any combination of stature and 

 weight. Using this plane to predict the heat which a woman of given 

 weight and stature would produce if she were a man, we have a series 

 of check or control values which is free from the disadvantages of the 

 empirical selected-group system. 



Using the equation 



h = -314.613+13.129 w+6.388 s 



based on men we have computed the theoretical heat-production for 

 each woman. 



We have treated the differences between the actual and the cal- 

 culated heat-production in three ways. 



The distribution of the deviation of the actual heat-production of 

 each woman from her computed production is shown in table 84, to 

 be discussed below. 



The mean theoretical and actual heat-productions for groups of 

 individuals classified by age, stature, body-surface by the Du Bois 

 height-weight chart, and body-weight have been calculated, and the 

 differences between theoretical and actual heat-production are recorded 

 under the caption "Prediction from weight and stature" in tables 

 77, 79, 80, and 81. 



Without a single exception the 39 comparisons indicate a lower 

 metabolism in women. The differences between observed and theo- 

 retical values range from 1.5 to 18.6 per cent in the case of groups 

 classified according to age, from 0.9 to 27.0 per cent in the case of 

 women grouped according to stature, from 2.9 to 25.8 per cent in the 

 case of subjects arranged according to their body-surface, and from 

 3.8 to 25.8 per cent in the case of groups of women assembled on the 

 basis of body-weight. 



14 Benedict and Emmes, op. cit. 



