Background: Globally, type 2 diabetes mellitus (T2DM) is one of the most common diseases, and the incidence is gradually increasing. Diet management could improve the elevated HbA1c levels. Aim: This review aims to examine the effects of different types of diets on glycemic control in patients with T2DM. Methods: PubMed and Google scholar databases were searched. Reports published from the years 1991 to 2021 that focused on the effect of different diets on diabetes control were selected. Results: All the studies reported that the type of diet can affect insulin secretion and glycemic control in patients with diabetes. The recommended macronutrient distribution for patients with diabetes is 30% of fat, 45-60% of carbohydrates, and 15-35% of protein. Consuming more or less of these macronutrients may lead to changes in glucose metabolism and may affect insulin secretion. In fact, following alow-fat diet improves glycemic control and decreases HbA1c levels. Studies reported that a low-carbohydrate diet had the greatest effect on improving glycemic control and insulin parameters. A low-calorie diet reduced fasting plasma glucose, while a very low-calorie diet resulted in a long-term decrease in HbA1c level. A healthy diet free of processed foods and sugar, and rich in nutrients such as fiber, vitamins, and minerals contributed to maintaining controlled blood sugar and lipid plasma levels. Although studies show a low-salt diet improves blood pressure, which is common inT2DM, other findings show that restricting salt intake is associated with increased sugar consumption. Conclusion: Healthy diet with adequate intake of energy and low-fat and low-sugar foods can enhance the glycemic control and reduce T2DM complications.
Keywords: HbA1c; Type 2 diabetes mellitus; dietary habits; glycemic control; low-carbohydrate diet; low-fat diet; very low-caloric diet.