Independent and combined effect of diet and exercise in adults with prediabetes

Prediabetes is defined as impaired fasting glucose and/or impaired glucose tolerance. Impaired fasting glucose is usually defined as fasting blood glucose between 5.6 mmol/L and 6.9 mmol/L (100.8-124.2 mg/dL), and impaired glucose tolerance is the 2-hour oral glucose tolerance test of 7.8-11.0 mmol/L (140.4-198.0 mg/dL). Most individuals with prediabetes are overweight or obese and are at greater risk of type 2 diabetes (T2D). The first line of treatment for individuals with prediabetes is lifestyle modification, including diet and exercise. The aim of this review, through the revision of primarily randomized control trials, is to discuss the independent and combined effect of diet and exercise on the incidence of T2D, glycemic control, and weight loss in adults with prediabetes. Based on the available literature, lifestyle modification combining both diet and exercise is effective at reducing the incidence of T2D and improving glycemic control, even without a significant reduction in body weight. Thus, it is unclear whether weight loss, through lifestyle modification, is a cornerstone for improving glycemic control in individuals with prediabetes. The independent effect of diet or exercise alone on the improvement in glycemic control and/or reduction in body weight in individuals with prediabetes still requires more studies to draw a clear conclusion, considering the quality and quantity of available studies. As of now, the best diet and/or exercise program to improve glycemic control and body weight in adults with prediabetes is unknown.