Why exercise before breakfast may not be for diabetes patients

A 2013 review concludes that postmeal exercise is better than premeal exercise for managing hyperglycemia. The ideal scenario for diabetes patients is to use up the glucose from the meal as fuel for exercise rather than bring additional endogenous glucose into the blood. This is readily done by timing the exercise tactically: let a physical activity of moderate intensity coincide with the build-up of glucose in the blood from the meal. At this time insulin-to-glucagon ratio is high and hepatic glucose production is inhibited. Data scattered over several studies, when considered together, show that about 30 minutes postmeal is the time to start a moderate-intensity exercise for optimal efficacy. Exercising at other times--before breakfast, right after a meal, or late in the postprandial period--leads to exertion-related glucose elevation and the patients miss a unique opportunity to blunt the meal-related glucose peak.