Seven key issues were outlined for classifying overweight and obesity in adults. Of those issues, body mass index (BMI) was suggested as a way to measure obesity. BMI is a simple measurement that looks at the correlation between weight and height and measures it by a simple mathematical formula of weight in pounds divided by the square of your height in inches. That number is then multiplied by 703 and the resulting number is classified as obese if it is greater than or equal to 30.
BMI =(Mass(lb)/(height(in)2)) x 703
The National Institute of Health (NIH) provides a calculator on their website.
Those individuals who are young or are in midlife and having a BMI of 30 and over have shown a propensity to having a higher mortality rate but there is an ongoing discussion whether those numbers are also true for those who are old (70 to 79) or very old (80+). The study’s authors concluded that in the case of the old and the very old, BMI is a less effective assessment of body fat in old age and that for individuals classified as overweight there was a lower mortality rate than those whose BMI measured less than 25 (considered normal for other age groups). Gerontologists (experts in the field of aging) have tentatively concluded that the WHO recommendations are overly restrictive, that in fact the evidence suggests instead that lower BMI rather than higher BMI contributes more to mortality rates and that changes in BMI rather than BMI itself may drive mortality rates in those two age brackets. The authors of the study suggest that BMI stability in old age is a sign of health and recommended that clinicians should pay as much attention to fluctuation as they do to BMI as a shifting of BMI is more likely a sign that the (body’s) system is breaking down.