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I'm Rob Logan, Ph.D. senior staff National Library of Medicine for Donald Lindberg, M.D, the Director of the U.S. National Library of Medicine.
An intriguing meta-analysis of prior clinical research — recently published in the Journal of the American Medical Association — suggests overweight adults may have less risk of death than normal weight persons. While the research’s methods and findings were criticized by some nutrition and health experts, an accompanying editorial in JAMA suggests confirming an association between overweight and a reduced mortality risk requires more comprehensive clinical research.
First, the meta-analysis of 141 studies — with a combined sample of 2.88 million persons and more than 270,000 deaths — found adults with an overweight body mass index (a BMI of 25 to 29.9) experienced a significantly reduced statistical risk of all-cause mortality compared to normal weight adults. These findings remained consistent even after the researchers adjusted for participants’ smoking status, pre-existing diseases, and some other potentially confounding variables.
All-cause mortality also was statistically similar for the lowest obesity level (a BMI between 30-34.9) compared to normal weight adults (a BMI between 21-24.9). In contrast, the JAMA meta-analysis found higher levels of obesity and underweight were associated with a significantly increased risk of mortality.
BMI is a number calculated from one’s weight and height. A tool that calculates your BMI is available within the ‘health check tools’ section of MedlinePlus.gov’s weight control health topic page.
Immediately after the findings were published, some leaders in the field of nutrition and health questioned the methods used in the JAMA meta-analysis, and challenged the study’s overall conclusions. For example, Walter Willett M.D., Harvard School of Public Health, told NPR that BMI may not be the best measure to assess the relationships among health, weight, and mortality rates. Willett explained using BMI as a primary measure obscures the impact of a person’s overall health and fitness — and the inclusion of the latter could alter the conclusions made in the current JAMA meta-analysis.
Conversely, an accompanying editorial in JAMA notes the meta-analysis is based on (and we quote): ‘rigorous study selection criteria and statistical methods’ (end of quote). Two of the study’s primary authors are researchers at the highly-regarded National Center for Health Statistics within the Centers for Disease Controls and Prevention.
The editorial’s authors note the JAMA meta-analysis’ findings are consistent with similar, less comprehensive research.
The editorial’s authors add the JAMA meta-analysis (coupled with recent, similar findings) suggest but do not demonstrate an inverse relationship between overweight, lower obesity levels, and mortality that they call (and we quote) ‘the obesity paradox or reverse epidemiology’ (end of quote). The editorial’s authors explain recent, aggregate research additionally raises the question (and we quote): ‘Can overweight as defined by BMI actually have a protective association with mortality?’ (end of quote).
The editorial’s authors note the answer to the latter question is yet to be determined and add assessing the links among weight, health, fitness, and other characteristics with illness and mortality will require more comprehensive, refined analyses. They conclude (and we quote):’ Establishing BMI is only the first step towards a more comprehensive risk evaluation’ (end of quote).
Meanwhile, MedlinePlus.gov’s weight control health topic page provides an overview of weight and health risks in the ‘diagnosis/symptoms’ section (from the National Heart, Lung, and Blood Institute). An easy-to-understand, narrated introduction to weight management (provided by the Patient Education Institute) is available within the ‘tutorials’ section of MedlinePlus.gov’s weight control health topic page.
MedlinePlus.gov’s weight control health topic page also contains links to the latest pertinent journal research articles, which are available in the ‘journal articles’ section. Links to related clinical trials that may be occurring in your area are available in the ‘clinical trials’ section. From the weight control health topic page, you can sign up to receive email updates with links to new information as it becomes available on MedlinePlus.
To find MedlinePlus.gov’s weight control health topic page, just type ‘weight control’ in the search box at the top of MedlinePlus.gov’s home page. Then, click on ‘weight control (National Library of Medicine).’ MedlinePlus also contains several other related health topic pages, including obesity and diets.
We should add while the JAMA meta-analysis was released at a time of the year when many commit to losing weight, its results and timing are not intended to undermine your commendable resolve.
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A disclaimer — the information presented in this program should not replace the medical advice of your physician. You should not use this information to diagnose or treat any disease without first consulting with your physician or other health care provider.
I hope you have a very happy holiday season and enjoy a healthy New Year. The National Library of Medicine and the ‘Director’s Comments’ podcast staff, including Dr. Lindberg, appreciate your interest and company — and we hope to find new ways to serve you in 2013.