A Few Extra Pounds Can Benefit Older People

Overweight participants in the cohort study had the lowest 10-year mortality. Normal-weight and obese participants ages 70 to 75 had a similar and slightly higher risk of death, Leon Flicker, PhD, of the Western Australian Center for Health and Aging in Perth, and colleagues found.

The findings add to evidence suggesting that being overweight in older age is not such a bad thing and might even be beneficial.

"These results lend further credence to claims that the body mass index [BMI] thresholds for overweight and obese are overly restrictive for older people," the researchers concluded in an article in the Journal of the American Geriatrics Society.

The authors also found that a sedentary lifestyle doubled the mortality risk for older women but did not affect survival of older men.

The World Health Organization has established four BMI thresholds to characterize body weight:

• <18.5 kg/m², underweight
• 18.5 to 24.9 kg/m², normal weight
• 25 to 29.9 kg/m², overweight
• ≥30 kg/m², obese

The authors noted that the thresholds were derived primarily from studies of younger and middle-age adults. Whether the cut points for overweight and obese are appropriate for older individuals has remained unclear.

Two systematic reviews and a meta-analysis showed no increased mortality risk associated with a BMI in the overweight range for older people (Arch Intern Med 2001; 161: 1194-1203, Obesity Rev 2007; 8: 41-59). However, methodologic differences complicated the comparison of different studies, Flicker and colleagues wrote.

So they sought to address some of the uncertainty by analyzing data from two large Australian cohort studies involving more than 9,000 individuals ages 70 to 75 (4,677 men, 4,563 women). The principal objectives were to determine the BMI threshold associated with the lowest mortality in older people and to determine whether the relationship between BMI and mortality differed between men and women.

Data for the analysis came from self-reported measures of height and weight, which the authors used to calculate BMI for the study participants. Participants also provided demographic, lifestyle, and health information.

Using the WHO criteria for BMI, the authors found that 1.3% of men and 3.1% of women were underweight; 43.5% of men and 50.3% of women were normal weight; 44.3% of men and 33.5% of women were overweight; and 11% of men and 13.1% of women were obese.

During 10 years of follow-up, overweight study participants had a 13% lower risk of death compared with normal-weight participants (HR 0.87, 95% CI 0.78 to 0.94). Obese participants had a mortality risk similar to that of normal-weight participants (HR 0.98, 95% CI 0.85 to 1.11).

Self-reported sedentary lifestyle doubled the mortality risk for women across all BMI categories. In contrast, sedentary lifestyle increased the mortality risk for men by 28%. Separate analyses involving common causes of death, such as cardiovascular disease and cancer, showed similar relationships between BMI and mortality risk. "Even after removing the effects of early mortality, those who were overweight were still at lowest risk, a finding consistent with the observation that weight loss in older age groups is associated with greater mortality," the authors wrote.

"Overweight older people are not at greater mortality risk, and there is little evidence that dieting in this age group confers any benefit," they added.

Flicker L, et al "Body mass index and survival in men and women aged 70 to 75" J Am Soc Geriatr Soc 2010; DOI: 10.1111/j.1532-5415.2009.02677.x.