Assessment of percent body fat content in young and middle aged men: skinfold method v/s girth method.SS Hegde, SR Ahuja
Dept of Physiology, Grant Medical College, Byculla, Bombay, Maharashtra.
Percent body fat content was found in apparently normal healthy 30 young (17-20 Yrs.) and 30 middle aged men (30-46 Yrs.) by measuring the skinfold and girth. None of the subjects were athletes or did regular physical exercise. Body density was calculated using mean of the four skinfold measurements as per the equations advocated by Durnin and Womersley, while percent body fat content was calculated from the body density by the Siri's equation. The mean % body fat content by this method in young men was 15.87 +/- 3.85% and in middle aged men was 24.75 +/- 3.55%. Ten percent of the young subjects and 90% of the middle aged subjects were found to be obese. Percent body fat content was also calculated from the girth measurements as advocated by McArdle et al. The mean of % body fat content with this method was 14.91 +/- 3.82% in young men and 24.30 +/- 3.35% in middle aged men. On comparison, the difference in percent body fat content calculated by both the methods was found to be significant in young men but not for middle aged men. The correlation, coefficient between girth method and skinfold method was 0.95 in case of young men and 0.90 for middle aged men. Therefore, we advocate that girth measurements can be used to determine percent body fat content, main advantage being simplicity of technique and requirement of inexpensive instruments for measurement.
Keywords: Adipose Tissue, Adolescent, Adult, Age Factors, Anthropometry, methods,Body Composition, Body Constitution, Human, Male, Middle Age, Obesity, diagnosis,Reproducibility of Results, Skinfold Thickness,
Obesity has been recognised as a major health problem in the past two or three decades. A male having a percentage body fat content of more than 20% is labelled as obese and in case of females, it is 30%. The fat content of the human body has physiological and medical importance. Recent evidence indicates that it is excess fat and not body mass percent that drives the relationship between body mass and increased risk for various diseases,. Hence early recognition and assessment of obesity is important. The traditional method of assessing obesity by comparing the individuals weight for the same age, sex and weight has been shown to be unsound. By this method an individual with good muscular development but little fat can be classified as obese. A more desirable alternative is to determine body fat, for which simplified methods have to be developed, stressing validity and reliability to large segments of population.
Anthropometry is a common field method for measuring body density, which includes measurement of skin-fold thickness and girth. A high degree of correlation exists between body density and measurements of skin-folds, and girth.
The purpose of this study is to determine percent body fat content in a group of young (1720 years) and middle aged men (above 30 yrs) by measuring both, skin-fold and girth and comparing the results obtained.
The study was carried out on apparently normal healthy, 30 young (17-20 Yrs.) and 30 middle-aged men (30-46 Yrs.). The subjects varied in body type, degree of physical activity and nutritional status. None of the subjects were athletes or did regular physical exercises. The measurements of skin-fold and girth were taken by an expert in the field.
Measurements of Skin-fold: Recommendations published by the committee on nutritional, Anthropometry of the Food and Nutrition Board of the National Research Councils were followed. A Lange's calliper was used with a constant calliper pressure of 102 g/MM2. The calliper had rectangular jaw faces measuring 40 mm. Three to five replicate measurements were taken on the right side of the body with subjects standing and mean of this was expressed as skin-fold score. The skin-fold thickness was measured to the nearest mm. except for low values (usually less than 5 mm or less), in which case it was taken to the nearest 0.5 mm. Four sites chosen were biceps, triceps, sub-scapular and suprailiac. Body density in gms/cc derived from the sum of these four skin-fold thickness scores using the equations of Durnin and Wornersley. Percent body fat content was then calculated from the body density values using the Siri's equation. The precision of this method in estimating percent body fat content is reported to be ± 3.5% body fat.
Measurements of Girth: Measurements were made according to the specifications given by McArdle et al. A flexible plastic measuring tape was used for measurements. To avoid skin compression, the tape was applied lightly to the skin surface so that it remains taut but not light. Thus, errors in recording with the subject standing in a relaxed position and rounded up to the nearest 1/4th inch. Duplicate measurements were taken at each site to calculate mean.
The sites measured for each age group were different and were as follows:
(a) Young age group - Upper arm (RUA)
- Forearm (RFA)
- Abdomen (ABD)
(b) Middle age group - Buttock (B)
- Abdomen (ABD)
- Forearm (RFA)
Percent body fat content was calculated directly by using prediction equations add constants presented by McArdle et al. The error in prediction is generally between ? 2.5 to 4.0%. To find out differences between two groups, the data (mean and standard deviations for all the variables) were compared using an unpaired ‘t’ test. The results of both the methods in a particular group was compared using paired ‘t’ test and correlation coefficient was calculated.
As illustrated in [Table - 1], the skin-fold and girth measurements were found to be significantly greater (p < 0.05).
The two variables indicate mean and standard deviation in the middle-aged men as compared to young men. The greatest difference in measurements was for abdominal girth and suprailiac skin-fold. Similarly, percent body fat content calculated by both the methods was significantly higher (p < 0.01) in the former group of middle-aged subjects.
According to the [Figure:1], in the younger males, the % body fat content, by girth method was less except in two cases and the difference of 0.96%. In case of middle-aged men [Figure:2], the % body fat content by girth method was less, except in thirteen cases. The difference in % body fat content obtained by both the methods ranged from a low of 0.07 to 2.8%, with a mean difference of 0.47% The girth method gave lesser values than the corresponding values obtained from skin-fold method in 15 out of 60 cases. The correlation coefficient of the two sets of values obtained by the two methods was r = 0.95 for young subjects and r = 0.90 for middle aged subjects. Further analysis of the data showed that the mean of % body fat content obtained by the girth was significantly lesser (t = 8.36, P<0.01) than the corresponding values obtained from skin-fold measurements in case of young men. But the difference between the values obtained by both the methods was statistically insignificant (t =1.47, P>0.05) in case of middle-aged men.
Body density and percent body fat content of young and middle-aged men in various geographic regions of the world are compared with the results obtained in the present study in the [Table - 2].
As seen in [Table - 2], the subjects from young age group included in our study had less body density whereas their percent body fat content was high as compared to the other studies. The only exception was the study carried out by Katch and McArdle where the results were comparable.
In case of middle aged men, the subjects in the study done by Pollock et al were less fat and that done by Jackson and Pollock  were more fat as compared to the subjects, in the present study. The middle-aged men in the study done by Katch and Behnke had a very low % body fat content (19.8%) probably because it was done on military personnel who underwent rigorous training routine. Climatic and seasonal variations, as well as genetic factors, probably account for the difference observed in body composition measurements between groups.
As we have said earlier, a person is termed as obese it he has more than 20% of his body weight as fat in case of males, In the present body study, in case of young subjects 10% of them were obese and in case of middle aged men 90% of them were obese. The tremendous increase in the percentage of obese people in the older age group can be noted. This is definitely going to influence the morbidity and mortality.
From the results of this study, it is not possible to conclude which of the two methods is more valid for the measurement of body fat. This can only be answered by following each measure with a direct chemical analysis. However, this method is impracticable for human subjects. The percent body fat calculated using skin-fold measurements along with Siri's equations is reported to have a precision of + 3.5%. Our results show that girth method is comparable to skin-fold method, and therefore we feel that it can be recommended for regular use in our population.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]