In a recent study published in Nutrients, researchers elucidate various exercise parameters, such as timing, type, intensity, and volume, influence post-meal glucose responses in healthy and diabetic individuals.

Study: Exercise Prescription for Postprandial Glycemic Management. Image Credit: C_Production / Shutterstock.com

Does exercise timing affect postprandial glucose responses? 

Exercise improves blood flow in active muscles and microvascular recruitment, thereby increasing glucose uptake and reducing its levels in the blood. However, nutritional state at the time of exercise is a crucial factor in the fluctuation of blood glucose levels.

Pre-meal exercise induces insulin sensitivity and fat oxidation by promoting glycogenolysis, which subsequently stabilizes blood glucose levels and prevents hypoglycemia. In the prandial state, glucose is primarily derived from exogenous sources.

The timing of exercise after meals plays an important role in managing blood glucose levels after eating. Recent physical activity guidelines for people with type 2 diabetes (T2D) recommends exercising after meals to efficiently control postprandial glucose levels.

The effect of exercise, especially when performed 12-16 hours before eating, is significantly less for acute blood glucose management. However, moderate-intensity aerobic or resistance exercise 20-45 minutes before a meal leads to significantly lower post-meal glucose levels. 

Thus, the performance of exercise closer to any meal leads to optimal benefits in glucose management. As compared to pre-meal exercise, post-meal exercise has greater benefits in controlling blood glucose levels for both non-diabetic and diabetic individuals. Several factors, such as exercise intensity and volume, and nutrition status, are responsible for the differential effects of pre- and postprandial exercise.

For healthy individuals, glucose levels peak 30-60 minutes after eating. However, glucose levels peak 60-120 minutes after a meal in people with T2D. Considering findings from multiple studies, postprandial exercise before glucose levels peak has been recommended at approximately 15 and 30 minutes in healthy individuals and people with diabetes, respectively.

Which exercise type Is most effective in maintaining blood glucose levels?

Both aerobic and resistance exercises, particularly in combination, play a significant role in the long-term management of glucose levels in people with T2D. In fact, any form of exercise is recommended to people with T2D to improve their glucose response after a meal. 

Among the various forms of exercise, cycling at varied intensities significantly reduces post-meal glucose excursions. Furthermore, a 30-minute moderate-intensity walking, elliptical exercise, cycling, or jogging lowers post-meal glucose peak and three hours of postprandial glucose levels in non-diabetic/healthy people. Alternative exercises, such as stair climbing and descending, also have beneficial effects on glucose management in people with diabetes.

Circuit and traditional resistance training significantly reduce postprandial blood glucose levels. After breakfast, 15-30 minutes of circuit resistance training significantly reduces blood glucose levels in both healthy and diabetic individuals.

Alternative muscle training programs, such as neuromuscular electrical stimulation (NMES), also decrease glycemic levels in both healthy individuals and those with T2D. For optimal benefits, 30 minutes of passive NMES followed by 30 seconds of work with 60 seconds of rest has been recommended. Voluntary muscle contractions in the lower limbs also reduce glucose peaks.

Exercise duration and intensity for optimal postprandial glycemic levels

Exercise volume, duration, and intensity must be suitably customized to accommodate an individual’s capacity. To date, no clear guidelines have been published on the optimal exercise volume to control post-meal glucose levels.

Exercise intensity must be tailored in terms of exercise duration, health condition, personal capacities, and p. For example, some people prefer shorter durations of high-intensity exercise, whereas others enjoy a longer session of moderate-intensity exercise.

The most recent guidelines for diabetic people are 45 minutes of exercise at any intensity to improve post-meal glucose management; however, there are many limitations to this recommendation. For example, high-intensity exercise could be challenging to perform shortly after a meal, which could increase gastrointestinal disturbances and hepatic glucose production. Therefore, a better exercise volume prescription is required to improve postprandial glucose responses.

Several studies have shown that exercise duration of 10-120 minutes can positively affect post-meal glucose responses in both non-diabetic and healthy individuals. Exercise sessions of 30-60 minutes have been consistently associated with improvements in postprandial blood glucose levels.

Likewise, 30-minute moderate-intensity aerobic exercise significantly improves postprandial glucose responses similar to that of a 45-minute session. A shorter duration of light-intensity exercise also has beneficial effects on blood glucose levels and glucose peaks, which is comparable to longer durations of exercise.