Study after study has shown a clear link between overweight and obesity, as defined by a high body mass index (BMI), with an increased mortality risk. However, new research indicates using BMI as a tool to measure health risk in older individuals may not be so accurate.
What is BMI
Body mass index is calculated using an individual's height and weight. Weight in kilograms is divided by height in centimeters squared. BMI is frequently used to assess overall health. The World Health Organization currently sets four categories for BMI measurements:
Under 18.5 = underweight
18.5-24.9 = normal weight
24.9-29.9 = overweight
Greater than 30 = obese
Researchers point out that these categories were determined based on studies of consisting of mostly younger and middle-age adults.
BMI May Not the Perfect Tool for the Elderly
An Australian study followed 9,240 men and women between the ages of 70 and 75. The study found individuals who were overweight according to their BMI had a 13% reduced risk of mortality for all causes. These findings are consistent with observations that weight loss in the elderly is linked to greater mortality. It's suggested that as we age nutritional reserves in the form of fat is protection in the case of illness.
A 2005 Canadian study followed 11,000 participants and found underweight adults had a 73% greater mortality risk versus those of normal weight. Interestingly, those who were overweight had a 17% reduced risk.
Also, a 2007 CDC study indicated overweight adults were at reduced risk of dying from infections, lung disease, and Alzheimer's.
Recommendations
Now, I in now way want to convey that being overweight is good for your health. I'm sharing these studies to show how BMI is just one tool for assessing your overall health and it's not perfect. Body fat plays a key role in your health risk and this is a factor BMI does not measure. An accurate evaluation of your health risk requires a variety of measurements, such as BMI, body fat percent, waist-to-hip ratio, etc.
Even though BMI recommendations for those over 70 may not need to be as "strict", it is still critical for elderly individuals (and everyone!) to remain physically active. Being sedentary doubles mortality risk for women and increases the risk for men 28%.
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