Major studies have denoted an association between poor glycemic control and the development of micro- and macrovascular complications in type 1 and type 2 diabetes mellitus. Current strategies aim to achieve the best possible control include a nonpharmacological approach consisting of lifestyle intervention using physical exercise, modification of nutritional intake and smoking cessation, combined with pharmacotherapy. Such an approach is also potent in preventing type 2 diabetes in patients with impaired glucose tolerance. This chapter will emphasize on the nonpharmacological approaches that are part of the therapy for both the diabetic and the prediabetic state. The main issues being considered are medical nutrition therapy, physical activity and exercise, behavioral therapy and smoking cessation and the issues are well explicated. Additionally, topics such as diet prescription, evaluation and progress, effectiveness of MNT, glycemic index of foods, practising carbohydrate counting in diabetes, fibre intake, clinical implications and yoga in patients with diabetes mellitus are discussed.