Accuracy and Usefulness of BMI
Introduction
The Body Mass Index (BMI) is the most well known measurement of an individual’s
body fat content based on height and weight, yet it has come under recent criticism
for being unreliable and inaccurate. This experiment was conducted in order to
determine if the BMI is an accurate, consistent measurement of an individual’s body
fat content. Students of Clemson University participated in the study during a month
long period and results indicate that the Body Mass Index is not an accurate
indicator of body fat content and may be a misreading of data. Further studies are
currently in process with a larger simple random sample in order to draw stronger
conclusions and reduce bias.
Procedures
In this experiment, two researchers went to Fike Recreational Center in Clemson
University and randomly selected students to participate in the experiment.
Participants volunteered anonymously with no external reward. For each individual
student their height was measured in meters and weight was recorded in kilograms
by the researchers. These two values measured by the researchers were used to
calculate the student’s BMI using the following equation:
BMI = weight (kg)
height (m)2
The student’s body fat content was then measured by the skin fold caliper and
recorded. These two measurements for body mass content were grouped according
to gender and then analyzed to draw conclusions.
Results and Discussion
The experiment went as expected with no unusual events or unpredictable data
points. A total of 57 men and 44 women measured to find the following data:
Men
Women
Body Mass Index
27.6
26.1
Skin Fold Caliper
22.2
23.9
Given our sample, we concluded that the Body Mass Index was significantly higher
than the body fat content measured using the Skin Fold Caliper. There are many
explanations for this; however, exact cause of the misreading using BMI can only be
determined with further studies and research.
Upon further literary research, we found that others studies concluded that
BMI is an inaccurate indicator of body fat content. BMI does not take into account
muscle mass, bone density, overall body composition and racial and sex differences
during calculation. Even though it takes an individual’s raw data and translates it
into a scale of numbers used to compare body fat content, these raw data points are
biased and therefore lead to an inaccurate number. An individual’s muscle mass and
bone density are mistranslated as fat content in the individual and give an
inaccurate reading. Even though Body Mass Index seems like an accurate
measurement of body fat content, current literature and studies have found that
many other measurements are more accurate.
Although the results found were statistically significant, they may have been
drawn from an unrepresentative sample. The sample used to measure BMI was
taken from students at the Fike Recreational Center at Clemson University, which is
the local gym on the college campus. It may be assumed that these students are
more conscientiously aware of their weight and body fat content and therefore will
have lower BMIs. In experiments it is normally best to draw data from a simple
random sample, where each individual in the population has an equally likely
chance of being picked to participate in the student. Samples with a larger sample
size, or more participants, are generally more valid due to the large number of
participants being able to outweigh potential outliers in analysis. It is likely that bias
was introduced into the sample due to convenience sampling and having a smaller
sample size. Although the bias may not be apparent and cannot be directly
measured, it may be in the sample and could affect the outcome of the study.
Conclusion
Overall, the experiment succeeded in measuring the body fat content of 101 college
students at Clemson University using both the Body Mass Index and Skin Fold
Caliper methods. The two methods were compared, with the Skin Fold Caliper
method being the accepted true value, and it was found that the BMI was inaccurate
and a misrepresentation of the individual’s true body mass content. Further
research on this subject is being planned with a larger sample size and simple
random sample in order to reduce bias and produce stronger data.
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