Engeland et al analyzed prospective data for over 2 million Norwegians ages 20-74 years with measured heights and weights who were followed up for 22 years. Those researchers suggested that the normal range of BMI should be shifted upwards because higher mortality rates were observed in the lower part of the normal range than in the lower part of the overweight range.
These examples are not just results from a “handful” of studies. In 2001, Heiat and colleagues evaluated the published literature on weight and mortality in the elderly (among whom more than 70% of all deaths occur) and concluded that “studies do not support overweight, as opposed to obesity, as conferring an excess mortality risk.” More recently, Janssen analyzed data from 26 published studies and similarly found no evidence of excess mortality associated with overweight among the elderly.
These are just a few examples from many studies that report results similar to ours. These show that our findings should not be considered “startling.” Our article takes its place in a long line of studies that have come to similar findings – that the mortality risk of people in the overweight category is pretty much the same as the mortality risk of people in the normal weight category. Some studies show a modestly higher mortality risk for people in the overweight category and others show a slightly lower risk.
Raeburn quotes Harvard professors Walter Willett and Meier Stampfer as stating that because our national sample included current and former smokers and people with chronic illness, we used the “wrong comparison group.” However, in our study we controlled for factors like smoking and illness that might confound the relationship between weight and mortality. In addition we ran several analyses to check whether our results could have been affected by smoking or pre-existing chronic illness. These analyses were published by CDC on its website in 2005. We also ran yet more detailed analyses that were posted on-line by the American Journal of Epidemiology in August, 2007, before Mr. Raeburn’s article appeared, followed by a print version in October. The analyses show that after the exclusion of smokers and those with possible illness-induced weight loss (as recommended by Drs. Willett and Stampfer), overweight was still not associated with excess mortality risk. This refutes the idea that we used the “wrong comparison group” or that our results would have been appreciably different if we had followed the procedures recommended by Drs. Willett and Stampfer and discarded most of our data.
Katherine M. Flegal, Ph.D.
Centers for Disease Control and Prevention
Barry I. Graubard, Ph.D.
National Cancer Institute
David F. Williamson, Ph.D.
Visiting Professor, Rollins School of Public Health
Mitchell H. Gail
National Cancer Institute
Disclaimer: The findings and conclusions in this commentary are those of the authors and not necessarily those of the agency.
Excess Deaths Associated with Underweight, Overweight, and Obesity. Katherine M. Flegal et al. in Journal of the American Medical Association, Vol. 293, No. 15, pages 1861–1867; April 20, 2005.
Cause-Specific Excess Deaths Associated with Underweight, Overweight, and Obesity. Katherine M. Flegal et al. in Journal of the American Medical Association, Vol. 298, No. 17, pages 2028–2037; November 7, 2007.
The Effect Of Obesity On Disability Vs Mortality In Older Americans. Soham Al Snih et al. in Archives of Internal Medicine, Vol. 167, No. 8, pages 774-80; April 23, 2007.
Associations Between Body Composition, Anthropometry, And Mortality In Women Aged 65 Years And Older. Chantal M. Dolan et al in the American Journal of Public Health, Vol. 97, No. 5, pages 913-8; May 2007.