Posted Thursday, 4 February
Revise Body Mass Index for seniors
Adults aged 70 and over who are classed as overweight under the current Body Mass Index (BMI) definition are less likely to die over a 10 year period than their normal weight counterparts according to Professor Leon Flicker, director at Western Australian Centre for Health and Ageing (WACHA).
He is calling for a revision of BMI for this group so it more accurately reflects lowest mortality risk.
He suggests people who live to their 70s and beyond may have a different relationship between body fat and risks to health than younger people.
The findings of the 10 year research project have been published online in the January issue of The Journal of the American Geriatrics Society.
BMI is a simple ratio of weight to height that is commonly used to classify underweight, overweight and obesity in adults: it is widely used in research and also in clinical practice, for instance in helping to explain concepts of obesity and overweight to patients.
Professor Flicker said that concerns are being raised about whether older people should be encouraged to lose weight, and so they wanted to address the question: "What level of BMI is associated with the lowest mortality risk in this group?"
For the study, Professor Flicker and colleagues examined health and lifestyle data on 9,200 men and women who were already enrolled in the Health in Men Study and the Australian Longitudinal Study of Women's Health.
They found that participants aged 70 and over whose BMI fell into the overweight range (as per the current WHO thresholds) were less likely to die in a 10 year period from all causes of death than counterparts whose BMI fell into the normal weight range.
This was also the case for common causes of death such as cancer and cardiovascular disease.
Being sedentary doubled the risk of death for women but only increased the risk by a quarter for men.
"Overweight older people are not at greater mortality risk than those who are normal weight. Being sedentary was associated with a greater risk of mortality in women than in men," the research concluded.
The BMI thresholds for overweight and obese are overly restrictive for older people.
The researchers pointed out that the survival benefits were only seen in the overweight category and not in those people who were classed as obese.
"The study shows that those people who survive to age 70 in reasonable health (and hence participate in these studies) have a different set of risk and benefits associated with amount of body fat compared with younger people,” Professor Flicker said.
