"Body-Mass Index and Mortality among Adults with Incident Type 2 Diabetes"
NEJM
http://www.nejm.org/doi/full/10.1056/NEJMoa1304501
"CONCLUSIONS

We observed a J-shaped association between BMI and mortality among all participants and among those who had ever smoked and a direct linear relationship among those who had never smoked. We found no evidence of lower mortality among patients with diabetes who were overweight or obese at diagnosis, as compared with their normal-weight counterparts, or of an obesity paradox. (Funded by the National Institutes of Health and the American Diabetes Association.)"