Dr. Dennis Van Hoof, PhD, CLC
“Master your diabetes management with proper timing.”
Timing for excellent diabetes management
When you start exercising, your muscles will first use the glycogen that they have already stored inside (see Blog post “The bitter-sweet truth” about glycogen) to generate energy (green lines in the graph below); high-intensity activities (dark green) will deplete these stores faster than low-intensity activities (light green). At the same time, your muscles will start taking up the glucose that is circulating in the blood stream, which will lower your blood glucose level (dotted purple line). This is a signal for your liver to release sugar into the blood stream to increase it again and regain the balance (solid purple line). Besides sugar, fat is also made available as a secondary fuel source (orange line).
All these processes are initiated as soon as you start exercising. However, some of these processes happen instantly, like burning up the glycogen stores inside the muscles, whereas others take time to reach their max, like mobilizing and burning fat. High-intensity exercise will burn up the glycogen stores in muscles faster than the liver can supply it to the muscles through the blood stream. This makes you feel exhausted before you reach optimal fat-burning mode. So if you want to burn fat, then take it easy in the beginning of your physical activity, so that your body can transition from glucose burning to fat burning mode.
Timing of eating sugary/carb-rich foods – It is best to eat sugary/carb-rich foods primarily before and right after physical activity, so that these sugars will be used to fuel your muscles and replenish the depleted glycogen stores. If you eat them when you are not going to be physically active (for instance before you start your desk job or go to sleep), the sugar is likely to be converted into fat and ends up in your body where you don’t want it.
When planning to do a short, high-intensity exercise, it is OK to eat something with a relatively high glycemic index (see Blog post “The bitter-sweet truth” for more information about glycemic index). When you plan to go for a long hike or other low-intensity endurance exercise, it is best to choose something with a low(er) glycemic index to keep you fueled for a longer time.
Important notes to Diabetics – If you have Diabetes, you must always carry extra sugar-rich foods with a high glycemic index (for instance dextrose tablets or honey pouches) in case of a hypoglycemic event.
You may allow your blood glucose level to be slightly elevated above what is considered the healthy upper limit of 130 mg/dL before starting your exercise to prevent dipping below 80 mg/dL. However, do not allow your blood glucose to rise to the point where ketoacidosis occurs.
Timing of insulin administration for Diabetics – Since fast-acting insulin types peak after 15-20 minutes of administration (see Blog post “Insulin and Diabetes“), avoid strenuous activities at that time. Keep in mind that the blood glucose lowering effect of “fast” insulin can linger for 4 hours after injection or bolus administration; its activity will slowly dwindle over time until it is cleared from the blood stream. It is best to start your exercise far beyond the peak activity of insulin; preferably 3-4 hours after insulin administration, so that there is no overlap. You may have to (temporarily) adjust your basal insulin level as well. But do not completely go without insulin, as this may trigger dangerous ketoacidosis (even when your blood glucose levels appear to be in a healthy range of 80-130 mg/dL).
With all this information, you can understand that timing is a crucial factor for scheduling your daily food consumption, physical activities, and regulating your blood glucose. But because we are all unique, we all like to do and eat different things, and we all want to live our own personal lives, there is no “one size fits all” plan.
The key to harmonizing a healthy and active lifestyle with excellent diabetes control is timing.
Timing of the right choices and portions of food with insulin administration to support your physical activities. And we are all familiar with the additional health benefits of exercise in addition to the double-punch effect on blood glucose lowering (see Blog post “Insulin and Diabetes“).
Keep an eye out for my next blog, and I hope to see you soon to get you started on the journey to your new life!
Dr. Dennis Van Hoof is a Certified Life Coach (CLC) with an academic PhD degree in Biochemical Physiology. By combining 20 years of first-hand personal diabetes experience with his in-depth scientific background, he developed a method to efficiently manage his own diabetes in a sustainable way. To learn how you can do this too, reach out for personal Diabetic Lifestyle Coaching or follow a group workshop that is specifically tailored to people with Type 1 or 2 Diabetes as well as pre-Diabetics and those at risk due to being overweight or obese. His clients thrive with their challenges and become an inspiration™ to others — with or without diabetes.