Aims/IntroductionThe impact of body mass index on mortality among patients with diabetes remains controversial. Therefore, we carried out a meta-analysis of pertinent studies. Materials and MethodsWe searched OVID/MEDLINE, EMBASE and Cochrane databases for all reported studies, which investigated the relationship between body mass index and mortality in patients with diabetes. Summary estimates of hazard ratios (HRs) were obtained with a random effects model. Univariate meta-regressions were carried out. ResultsA total of 20 studies including 250,016 patients with diabetes were identified. The results of the present study showed a significantly reduced risk of all-cause mortality in overweight patients (HR 0.82, 95% CI: 0.74-0.91, P < 0.0001, and I-2 = 91.6%) as compared with normal weight patients. The survival benefits of obesity were only observed in the elderly patients (HR 0.69, 95% CI: 0.63-0.75, P < 0.0001, and I-2 = 50.4%), but not in the younger patients (HR 1.01, 95% CI: 0.84-1.20, P = 0.96, I-2 = 80.1%). Furthermore, the beneficial prognostic impacts on overweight (coefficient = 0.030, P = 0.041) and obesity (coefficient = 0.032, P = 0.010) were attenuated with clinical follow-up duration. ConclusionsThe present meta-analysis showed a significantly lower risk of all-cause mortality in overweight patients with diabetes compared with normal weight patients. However, the survival benefits of obesity were only observed among the elderly patients.