Optimal BMI With Lowest Mortality Has Shifted to Higher Weight

MedicalResearch.com Interview with:
Shoaib Afzal, MD, PhD
Department of Clinical Biochemistry
Copenhagen General Population Study
Herlev and Gentofte Hospital,
Faculty of Health and Medical Sciences
University of Copenhagen, Copenhagen, Denmark

MedicalResearch.com: What is the background for this study? What are the main findings?

Dr. Afzal: Previous findings indicate that while average BMI has increased over time in most countries, the prevalence of cardiovascular risk factors may be decreasing among obese individuals. Thus, the BMI associated with the lowest all-cause mortality may have changed over time. This study included three cohorts from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13,704) and 1991-1994 (n = 9,482) and the Copenhagen General Population Study in 2003-2013 (n = 97,362).

The increased risk for all-cause mortality that was associated with obesity compared to normal weight decreased from 30% in 1976-1978 to 0% in 2003-2013, that is, over a 30-year period. In addition, the optimal BMI for lowest all-cause mortality increased by 3.3 from 23.7 in 1976-1978 through 24.6 in 1991-1994 to 27 in 2003-2013. Another interesting finding in this study is that the optimal BMI in relation to lowest mortality is placed in the overweight category in the most recent 2003-2013 cohort.

MedicalResearch.com: What should readers take away from your report?

Dr. Afzal: Compared to in the 1970’ies, today overweight individuals have lower mortality than so-called normal weight individuals. The reason for this change is unknown, and its implications needs further investigations. However, these results would indicate a need to revise the categories presently used to define overweight, which are based on data from before the 1990s.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Dr. Afzal: Future research should focus on confirmation of our findings and on possible reasons for the shift seen in optimal BMI. Could it be due to improved treatment of hyperlipidemia, hypertension and diabetes caused by obesity? Or are general improvements in public health driving these changes?   

MedicalResearch.com: Is there anything else you would like to add?

Dr. Afzal: These results could only be obtained due to the 100% complete data in Danish national registries with respect to all-cause mortality. 

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.


Afzal S, Tybjærg-Hansen A, Jensen GB, Nordestgaard BG. Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013. JAMA.2016;315(18):1989-1996. doi:10.1001/jama.2016.4666.

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Last Updated on May 12, 2016 by Marie Benz MD FAAD