How to Workout Without Causing Hypoglycemia

Learn the best time of day to exercise to avoid blood sugar-related interference.

fasted cardio workoutIf you have type 1 diabetes, working out before breakfast may help you get a workout in without causing hypoglycemia.

There are very few things as frustrating in an otherwise ordinary day with type 1 diabetes as finding yourself collapsed in a chair chugging apple juice in the middle of your workout. Low blood sugars are the evil intruder of any power-walk or cross-fit workout, yoga class, bike ride or even half-marathon!  You name the type of workout; diabetes will find a way to interrupt it.

Low blood sugars force you to stop, eat, wait, and wait some more. Even when your blood sugar does stabilize 20 minutes later, you may have run out of time to finish your workout, or—if the low was severe enough—you’re completely drained of energy and the workout is over.

While there are a variety of ways you can adjust your insulin doses and time your carbohydrate intake to hopefully prevent low blood sugars during exercise, there is also one time of day you can exercise that is least likely to let diabetes get in the way.

Walking (or the exercise of your choice), on an empty stomach, first thing in the morning, with an in-range blood sugar. Also known as “fasted cardio.”

Running on Empty

This probably sounds crazy to you—I know. You’re probably thinking, “How could exercising without eating anything actually keep my blood sugar from plummeting?” I thought the same thing when this was first suggested to me 10 years ago by my former powerlifting coach, Andrew Berry—but I’m here to tell you that not only does it work, it’s based on basic human physiology, whether or not you have diabetes.

“Fasted cardio” is actually a weight-loss method that bodybuilders have been using for decades to ensure they are burning body fat for fuel rather than glucose during their cardio workouts as they prep to get on stage in nothing but a speedo.

But even if you’re not training to be the next Schwarzenegger, fasted-cardio or fasted__insert exercise choice here___ is incredibly helpful if you take insulin or other medications that lower blood sugar.

Why Fasted-Cardio Works

When you wake up, your body is in a fasted-state because you haven’t eaten for nearly 8 hours. This means your body is burning body fat for fuel, not glucose. If you were to step on a treadmill, without having consumed any calories (some can get away with black coffee), your body will continue to burn body fat for fuel—not glucose in your bloodstream—thus not causing your blood sugar to drop.

Alternatively, the moment you eat (even the cream in your coffee contains enough calories to trigger the switch), your body will begin to burn glucose primarily for fuel and your blood sugar will drop when you exercise unless other precautions with insulin and carbohydrate doses are taken.

This can be applied to cardio, yoga, strength-training, etc. Keep in mind that for many, a truly anaerobic strength-training workout can actually raise blood sugar, so you might actually need a dose of insulin if you find that fasted strength-training raises your blood sugar slightly in the morning. This isn’t a bad thing! It’s simply normal human physiology breaking down glycogen in your muscles, converting it to glucose and cycling it back to your muscles for fuel during your strength-training workout.

New Exercise Guidelines for Type 1s

In January 2017 a team of international researchers and clinicians led by York University (Toronto) Professor Michael Riddell published the first set of guidelines to help people with type 1 diabetes exercise safely. The research was funded by the Juvenile Diabetes Research Foundation (JDRF).

“Regular exercise can help individuals with diabetes achieve their blood lipid, body composition, fitness and blood sugar goals but for people living with type 1 diabetes, the fear of hypoglycemia, loss of glycemic control and inadequate knowledge around exercise management are major barriers,” say Professor Riddell in a press release adding that this is the first ever consensus guidelines from leading experts intended to help type 1s.

The authors noted that today there are more T1Ds that do not maintain a healthy body mass (BMI) or adhere to the minimum amount of recommended moderate-to-vigorous aerobic activity (150 minutes per week). The benefits of exercise include lower average blood glucose levels, requiring less daily insulin, less risk of cardiovascular disease, diabetic eye disease and other health issues.

In addition, the new report suggests that exercises helps people with type 1 diabetes achieve target levels of glycated hemoglobin (HbA1) levels, blood pressure levels and healthier BMI compared to inactive people with type 1.

3 Important Points to Keep in Mind Before Trying a Fasted-Cardio Workout

  1. The number one rule when performing fasted exercise, however, is that you begin your workout with an in-range blood sugar and accurate insulin doses. If you wake up low or you wake up high, that out-of-range blood sugar would need to be addressed appropriately, thus complicating and probably preventing your ability to perform fasted exercise of any kind. This is a great motivation for fine-tuning your nutrition and insulin doses before bed and through the night, to ensure your blood sugar doesn’t get in the way of your ability to workout first thing in the morning.
  2. If your have type 2 diabetes and are someone who doesn’t take insulin based on carb-quantities, but simply prescribed to take your fast-acting insulin “in the morning,” you would not take fast-acting insulin until you do eventually eat your breakfast. Taking your fast-acting insulin before your fasted exercise will lead to a low blood sugar.
  3. Lastly, because every human body has its exceptions and your medications and insulin doses may not be perfectly accurate, check your blood sugar before, during and after your first fasted exercise experiment to see what’s happening within your own body. And always keep fast-acting glucose nearby, such as a juice box or glucose tabs.

Want to learn more about balancing your blood sugar during exercise? Speak to a certified diabetes educator.

Updated on: February 7, 2019
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