To better quantify the health risks associated with obesity, the Pitt researchers, collaborating with researchers from six other institutions, examined the rates of death and of newly diagnosed coronary heart disease over a seven year period of 90,185 women in five specific weight categories. The women, all participants of the Women's Health Initiative-Observational Study, were assigned to the weight categories based on the weight-to-height ratio known as body mass index (BMI): normal (BMI 18.5 24.9), overweight (BMI 25.0 29.9), obesity 1 (BMI 30.0 34.9), obesity 2 (BMI 35.0 ¨C 39.9) and extreme obesity (BMI 40).
The study showed that white women in the obesity 1 category (approximately 60 pounds above a normal weight for a 5-foot, 5-inch tall woman) to have a 12 percent higher risk of death over the seven year follow-up period, but extremely obese women (approximately 110 pounds above a normal weight for a 5-foot, 5-inch tall woman) had an alarming 86 percent higher risk of death than their normal weight counterparts.
Death rates increased substantially with increasing weight category, ranging from 68.39 deaths per 10,000 person-years in women with normal BMIs to 116.85 deaths per 10,000 person-years in extremely obese women.
The study findings, according to lead author Kathleen McTigue, M.D., M.P.H., assistant professor of medicine and epidemiology, division of internal medicine, University of Pittsburgh School of Medicine, suggest that the particularly rapid rise in extreme obesity in the U.S. may exacerbate the health effects and health-related expenditures of the ongoing obesity epidemic.
Although one of the national health objectives for the year 2010 is to reduce the prevalence of obesity among adults to less than 15 percent, current data indicate that the situation is worsening rather than improving, Dr. McTigue points out. During the past 20 years, obesity rates among U.S. adults have skyrocketed with 30 percent of adults 20 years of age and older over 60 million people now categorized as obese and 9 million as severely obese. Over the past 25 years, the percentage of young people who are overweight or obese has more than tripled.
The prevalence of extremely obese women in the U.S. differs among racial and ethnic groups, with Asian Americans in this study having the lowest prevalence and African-Americans having the highest. The researchers note that they found no difference in the weight-related risk for death from all causes, death due to heart disease, and new onset of heart disease across the diverse racial and ethnic groups, although, they point out that the relatively small number of women from certain racial/ethnic groups limited their ability to examine these outcomes within all groups in detail.
The investigators also examined African-American and Caucasian women more closely, finding that both groups experienced increased risks of mortality and new onset of coronary heart disease with increasing weight category. In addition, the risk for diabetes and hypertension increased as excess weight became more extreme, and even women who were overweight but not obese experienced significant weight-related health consequences.
According to Dr. McTigue, these results suggest that degree of obesity has a major impact on health risk. "When a woman and her physician are choosing treatment options for obesity, they should carefully consider the degree of obesity, not just think of obesity as an overall entity. The degree of obesity will influence how likely it is that her health will be harmed by her current weight. These findings also underscore the importance of learning more about the best treatments for extremely obese women, as well as the need for aggressive diagnosis and treatment of diabetes, high blood pressure and high cholesterol in the obese," said Dr. McTigue.
The study was funded in part by the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH). In addition to Dr. McTigue, others involved in the study include Alice Valoski, M.S., R.D., and Lewis Kuller, M.D., Dr.P.H., University of Pittsburgh; Joseph Larson, M.S., Fred Hutchinson Cancer Research Center; Greg Burke, M.D., M.S., Wake Forest University; Jane Kotchen, M.D., M.P.H., Medical College of Wisconsin; Cora E. Lewis, M.D., M.S.P.H., University of Alabama at Birmingham; Marcia Stefanick, Ph.D., Stanford University; and Linda Van Horn, Ph.D., R.D., Northwestern University.
The University of Pittsburgh School of Medicine is considered among the nation's leading medical schools, renowned for both its curriculum that emphasizes both the science and humanity of medicine and for its remarkable growth in NIH grant support which has more than doubled since 1998. For fiscal year 2005, it ranked eighth among schools of medicine and, together with its university and hospital affiliates, ranked seventh among educational institutions, according to preliminary data. As one of the university's six Schools of the Health Sciences, the School of Medicine is the academic partner to the University of Pittsburgh Medical Center. Their combined mission is to train tomorrow's health care specialists and biomedical scientists, engage in groundbreaking research that will advance understanding of the causes and treatments of disease, and participate in the delivery of outstanding care.
Note to media: To view an interview of Dr. McTigue with comments about obesity from Madelyn Fernstrom, Ph.D., C.N.S., founder and director of the University of Pittsburgh Medical Center Weight Management Center and associate director of the UPMC Center for Nutrition, go to http://www.jama-archives.org/media/pastreleases.dtl.