Introduction: In this secondary analysis of the Metformin and AcaRbose in Chinese as the initial Hypoglycaemic treatment (MARCH) trial, we evaluated what demographic and clinical factors were associated with reduction in weight. We also assessed the effects of acarbose and metformin treatment on weight reduction. Material and methods: We analyzed the demographic and clinical laboratory values from the 784 patients with type 2 diabetes of the MARCH study who were treated for 48 weeks with acarbose or metformin. We determined the association of the different parameters with a weight reduction of >= 2 kg in patients using univariate and multivariate analysis. Results: In patients treated with acarbose, males were less likely than females to lose >= 2 kg of weight (p = 0.025). Higher baseline HbA(1c) levels and lower decreases from baseline in fasting plasma glucose (FPG) levels after 48 weeks of treatment were negatively associated with losing = 2 kg of weight (both, p < 0.05). Higher baseline glucagon AUC was also positively associated with reducing weight by >= 2 kg (p = 0.010). In patients treated with metformin, change from baseline in whole body insulin sensitivity increased the odds of having a weight reduction of >= 2 kg (p = 0.014). Conclusions: This study found that for both acarbose and metformin, control of FPG significantly impacted weight loss. Baseline AUC for glucagon in patients treated with acarbose and an increase of whole body insulin sensitivity after 48 weeks of treatment with metformin were important factors for weight reduction.