CLASSICS IN OBESITY

THE SPECIFIC GRAVITY OF
HEALTHY MEN
BODY WEIGHT + VOLUME AS AN INDEX OF OBESITY

A. R. Behnke, JK,M.D.
Lieutenant Commander, M. C., U.S. Navy

B. G. Feen, M.D.
Lieutenant, M.C., U.S. Navy

AND

W C. Welham, M.D.
Lieutenant, M.C., U.S. Navy

The fundamental biologic determination of corporeal specific gravity, essentially a relationship between weight and unit volume, has been neglected in the modem classification of healthy persons. Stern (1) and
Spivak (2) emphasized the value of the measurement of corporeal density, but their experimental data are not conclusive. Of especial interest is the relationship between gravity and the fat content of the body.
The presence of an indeterminate amount of excess adipose tissue renders difficult any precise computation, for example, of metabolic rate or dosage of drugs in terms of total body weight. The important consideration should be the weight of the lean body representing the active mass of protoplasm.
In this paper the data support the concept that the comparatively low specific gravity of fat makes the measurement of the specific gravity of the body mass valid for the estimation of fat content.
The comprehensive, statistical analysis of Boyd (3), however, covering seven hundred and eighty-seven values reported since 1906 does not permit a classification of individuals with respect to obesity. The analyzed results (3). moreover, obtained by different investigators
Behnke AR, Feen BG, Welham WC. The specific gravity of healthy men.
JAMA. 1942;118:495-498.
Copyright 81942. American Medical Association. Reprinted with permission from the American Medical Association,515 N. State St., Chicago, IL 64610.
Special thanks to Judy Roberts of the Pennington Information Center for help in acquiring this and reference documents.

elude comparison by reason of the unknown quantity of air present in the !ungs when the measurements were made. In tile present investigation the values of specific gravity obtained on ninety-nine healthy naval men in the
20 to 40 year age group were corrected by determining the residual air volume. The results obtained permit the classification of individuals as to degree of obesity and serve as a single index of physical fitness to supplement the standard age-height-weighttables which frequently lead to a designation of overweight for well developed men in contrast with a designation of normal weight for more obese individuals who fall into a lower weight group. METHOD OF PROCEDURE
The essential measurement is that of body volume, which, based on Archimedes’ principle, can be conveThe material in this article should be construed only as the personal opinion of the writers and not as representing the opinion of the writers and not as representing the opinion of the Navy Department officially.
1. Stern, H.: Investigations on Corporeal Specific
Gravity and on the Value of This Factor in Physical
Diagnosis, M. Rec. 59: 204-207, 1901.
2. Spivak, C. D.: The Specific Gravity of the Human
Body, Arch. Int. Med. 15: 628-642 (April) 1915.
3. Boyd, Edith: The Specific Gravity of the Human
Body, Human Biology 5: 646-672 (Dec.) 1933.

OBESITY RESEARCH Vol. 3 No. 3 May 1995 295

Classics in Obesity

TABLE
1 .-Example Illustrating the Method of Computing Specific Gravity
Pounds

Kilograms

183.00
14.20
23.20

83.20
6.45
10.55

13.75

6.25

Corrections
Gross weight in water...............................................................................................
Weight of belt ...........................................................................................................

23.20
13.75

10.55
6.25

Weight in water, not corrected for residual air.........................................................
Correction for residual air (1,200/453).....................................................................

9.45
2.65

4.30
1.20

Net weight in water