What is obesity - definition

Published on January 31, 2016   13 min

Other Talks in the Series: Obesity: Science, Medicine and Society

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Hello, my name is Dr. Andrew Walley. I'm senior lecturer in Human Genomics at St. George's University of London, and I am going to talk to you about how we define obesity.
In summary, I'm goint to talk to you about measures of obesity and the body mass index specifically, how we define obesity using BMI. The current population trends in BMI, so that you can see the global problem of obesity. The drawbacks of using BMI as a measure of obesity, and the other measures that are available to us within the field of obesity for measuring.
So how can we measure obesity? Well, the most obvious would be by weight, but you will see in a little while that body mass index is a preferred measure. Alternatives such as waist/hip ratio are used, and then we start moving into more accurate measures but more time consuming measures like skinfold thickness, impedance, air displacement, and imaging. And I'll talk to you about all of those later on.
So body mass index.
Why do we choose BMI? The main reason we choose BMI is because it's appropriate for large scale epidemiological studies. It can be measured very quickly, it's relatively reproducible, and most importantly it requires no expensive equipment. In addition, most genetic studies out there will measure weight and height as part of their basic measurements. So those studies can be incorporated into meta-analyses of BMI giving tens of thousands of subjects for analysis.
The body mass index is relatively simple to calculate. It's your weight in kilograms divided by your height in meters squared. So for example, I am 1.78 meters tall and I weigh 90 kilos, and that gives me a BMI of 28.4 kilograms per meter-square.