Patients with type 2 diabetes who are overweight but not obese live longer than those who are underweight or normal-weight, according to a study is published in Annals of Internal Medicine. Researchers call this effect the "obesity paradox."
Obesity is a known risk factor for cardiovascular disease and type 2 diabetes. Studies show that overweight patients with cardiovascular disease live longer than normal-weight patients with cardiovascular disease. To determine if the same could be true about patients with diabetes, researchers followed more than 10,500 patients with type 2 diabetes and no known cardiovascular disease for a median of 10.6 years and collected information about cardiovascular events and all-cause mortality. The overweight and obese patients had an increased risk for cardiovascular events, but those who were overweight had better survival rates compared to those who were underweight or normal-weight.
The authors offer a few possible reasons for the obesity paradox in type 2 diabetes. First, type 2 diabetes induced by the metabolic stress of obesity may fundamentally differ from that which develops in the absence of obesity. Second, patients with type 2 diabetes and a low BMI might have higher tobacco and alcohol consumption, contributing to both the development of diabetes and a lower BMI. Finally, obese patients may be more likely to be checked for diabetes, leading to earlier diagnosis. The researchers caution that these results do not suggest an ideal BMI and should not discourage patients from adopting a healthy lifestyle.
The Obesity Paradox in Type 2 Diabetes Mellitus, Annals of Internal Medicine, doi: 10.7326/P15-9015, published 4 May 2015.
The Obesity Paradox in Type 2 Diabetes Mellitus: Relationship of Body Mass Index to Prognosis: A Cohort Study, P. Costanzo, J.G.F. Cleland, P. Pellicori, A.L. Clark, D. Hepburn, E.S. Kilpatrick, P. Perrone-Filardi, J. Zhang, and S.L. Atkin, Annals of Internal Medicine, doi: 10.7326/M14-1551, published 4 May 2015.