A woman's weight in middle age -- especially pounds put on after age 18 -- appears to determine her health in old age, according to a new study.
Compared with women who were lean at age 50 and maintained a healthy weight as they aged, women who had a BMI of 30 or more had only about a 20 percent chance of being a healthy, disease-free septuagenarian, wrote Dr. Qu Sun, of the Harvard School of Public Health.
The findings, based on analysis of data from the Nurses Health Study, were published in BMJ Online First.
The researchers also found that women who were overweight (meaning a body mass index greater than or equal to 25) at age 18 and gained more than 22 pounds between 18 and 50 had the worst odds of healthy survival.
Moreover, "with each BMI category at age 18, those who gain more weight had lower odds of healthy survival," the authors wrote.
"Since body weight is a modifiable factor, the good news is that healthy aging is not purely the consequence of good genes or other factors that one cannot change. If women maintain a healthy weight as adults, they may increase their odds of enjoying a healthy life in their later years," Sun said in a statement.
In addition to overall weight gain, having more fat around the waist was also identified as a risk factor for unhealthy aging.
After adjusting for smoking, diet, and education, "increased waist circumference and hip circumference were each associated with reduced odds of healthy survival," the researchers wrote.
Of the 17,065 participants in the Nurses Health Study who survived until age 70, the authors identified 1,686 whom they dubbed "healthy survivors."
These women were free of 9 chronic diseases or conditions; cancer, diabetes, congestive heart failure, COPD, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis. Healthy individuals also had no evidence of cognitive impairment or limitations on physical function.
The other 15,379 Nurses Health Study participants who lived to age 70 were defined as "usual survivors," a mixed group of which 3.3 percent had chronic diseases but no limitations, 59.5 percent had cognitive, physical, or mental health impairments but did not have any major chronic disease, and 37.1 percent who had chronic conditions as well as cognitive, physical, and mental health limitations.
Dr. Mitchell Roslin, of Lenox Hill Hospital in New York City, said the study quantified "what should be obvious. While we think that obesity is inert, and other conditions deadly, the truth is that obesity and being sedentary is the major health problem in the U.S."
Roslin, who was not involved in the study, said "if we really want healthcare reform and healthier people, we need to curb obesity. Otherwise, the incidence of chronic disease will continue to increase, and no system will be able to contain costs."
The authors acknowledged a number of limitations in the study, including a primarily white study population, so the results may not be generalized all populations.