Patients with type 2 diabetes who are overweight/obese have lower all-cause mortality rates compared with those who have normal body mass indexes (BMIs) because of the obesity paradox, according to results published in Diabetes Care.
This effect was more pronounced among current smokers.
With the obesity paradox, being overweight/obese is associated with mortality benefits and is believed to be explained by confounding and reverse causality, rather than a genuine benefit of being overweight.
The study included the general UK Biobank population (n=502,631) and 3 subgroups of patients with type 2 diabetes (n=23,842), coronary heart disease (CHD; n=23,842), and cancer (n=45,790) at baseline. The researchers considered participants’ BMI (continuous and categorical), waist circumference, body fat percentage, and waist-to-hip ratio. The primary outcome was all-cause mortality.
When considering participants’ BMI, the researchers observed the obesity paradox among participants with type 2 diabetes, with an adjusted hazard ratio of 0.78 for obese vs normal BMI. However, they did not observe this effect among participants with CHD (adjusted hazard ratio, 1.00).
After adjusting for smoking status, the researchers found that the obesity paradox could still be observed in current smokers, but was absent in never smokers.
When the researchers considered other adiposity measures, they found less evidence for the obesity paradox. However, smoking status consistently affected the adiposity-mortality relationship.
“These data provide further insight into the potential mechanisms that link adiposity and mortality and deepen our understanding of the obesity paradox,” the researchers wrote. “However, more research is required to understand the true causal nature of these relationships before clinical guidance is modified.”
Jenkins DA, Bowden J, Robinson HA, et al. Adiposity-mortality relationships in type 2 diabetes, coronary heart disease and cancer subgroups in the UK Biobank, and their modification by smoking [published online July 3, 2018]. Diabetes Care. doi: 10.2337/dc17-2508.