It is generally accepted that exercise can improve blood glucose control and enhance insulin sensitivity. Several physiological processes may be responsible for these improvements, including the following:
- Adaptations in muscle insulin signaling[1]
- Glucose transporter type four (GLUT-4)[2] protein expression, content, and action
- Enhanced intramyocellular oxidative enzyme capacity[3]
- Increased muscle capillary density.[4]
However, it is not entirely clear whether exercising in the fasted state may be better than exercising in the fed state. Based on the available scientific evidence, it seems that being physically active and losing weight (through a hypocaloric diet) are the most important factors[5] for improving glycemic control and insulin sensitivity, while performing exercise in a fasted vs. fed state plays a minor role at most. However, the research comparing the effects of fed vs. fasted exercise on glycemic control and insulin sensitivity is still in its infancy, so it’s probably best to wait until there is more research before drawing definitive conclusions.