Like the rest of us, you were likely taught that exercising with type 1 diabetes requires carbohydrates. “Eat 15 grams of carbs before exercising, and you’ll be fine.”

It only takes a few weeks of actually living with type 1 diabetes to learn how over-simplified this advice truly is.

Instead of feeding your body carbohydrates before you hit the gym, go for a run, or sweat it out at your favorite yoga studio, I have a suggestion for you.

Don’t eat breakfast until after you exercise

What? Exercise on an empty stomach? But I’ll surely go low!”

That’s what you’d think based on the over-simplified diabetes management education we all received when we were diagnosed, but hear me out.

If you don’t consume calories first thing in the morning, your body remains in a “fasted” state, burning fat primarily for fuel. The moment you drink or eat calories, you are switching the flip that tells your body it’s no longer fasting and can now burn glucose in your bloodstream for fuel. 

The second perk to exercising before breakfast is that it means you don’t have a big dose of rapid-acting insulin in your bloodstream either. When you combine that insulin for your breakfast with exercise, you increase the chances of hypoglycemia tremendously because the exercise increases the amount of glucose your cells can take in. 

What about your coffee? Drinking black coffee really doesn’t translate to your body as a source of fuel. If you can’t drink it black, you might want to start experimenting with getting your tastebuds more used to the flavor of black coffee! I swear, once you give it a couple of weeks to adjust, you might really start to appreciate the real flavor of your coffee! (Do keep in mind, too, that coffee can trigger your liver to produce more glycogen and glucose, too, adding to your need for a little bit of insulin even if you don’t eat breakfast.)

Two Things That Can Raise Your Blood Sugar if You Exercise Before Breakfast

There are a few things that can actually cause your body to need a small dose of rapid-acting insulin prior to exercising before eating breakfast.

1. Dawn phenomenon: This pesky physiological detail of the human body is a surge of hormones (cortisol, glycogen, and growth hormone) that help your body function in the morning. It’s natural. It’s healthy. But it can cause a big blood sugar spike for many. (Personally, I never had a problem with this until my 30s!) If you’re going to exercise first thing in the morning on an empty stomach, you’ll likely need even just a ½ unit of rapid-acting insulin to account for this early morning hormone surge. I know my body needs 1 unit of insulin the moment I get out of bed if I’m not going to exercise. If I plan to exercise before breakfast, I cut that 1 unit dose down to a ½ unit. (Read more about managing dawn phenomenon.)
2. Anaerobic exercise (weights, spinning, sprinting) can raise your blood sugar: If you’re headed to Cross Fit or a spinning class, you may already know this type of exercise can easily spike your blood sugar at any time of day. This is because your body is breaking down muscle and stored glycogen, converting it into glucose and trying to cycle it back to your muscles to be used as fuel — over and over and over while you workout. If you try to do this type of exercise before eating breakfast, you could easily see a big spike in your blood sugar which means you’ll likely need a small bolus of rapid-acting insulin to counteract this effect. (Read more about why lifting weights spikes your blood sugar during and after your workout.)

Real-Life Examples of Exercising Before Breakfast

Here are two examples of making this pre-breakfast exercise approach part of my real life.

A 60-minute walk before breakfast

Scenario One

It’s 7 a.m. on Saturday morning. I’m out of bed, and I’ll be going for an hour-long walk (aerobic exercise) at 8 a.m. with my best friend. My blood sugar is 95 mg/dL. If I do nothing, I know from past experiments that my blood sugar will have spiked all on its own to 160 mg/dL from the effects of the dawn phenomenon.

If I continue to do nothing, that 160 mg/dL will rise to 250 mg/dL by 9 a.m.

But I also know, if I take my usual 1-unit of rapid-acting insulin immediately before an hour-long power-walk, I’ll end up low by 8:30 a.m.

Instead, I’ll take a ½ unit to prevent that spike, and let the exercise do the rest of the work to keep me in my goal blood sugar range.

Scenario Two

Now, what if I were to wake up at 7 a.m. and plan on exercising at 10 a.m.? That’s a bit of stretch — and really starts to approach an “intermittent fasting” schedule because you likely won’t be eating anything until closer to noon.

If this was my plan, I would take my full 1-unit dose of rapid-acting insulin at 7 a.m. because it will be mostly out of my system by the time I’m exercising at 10 a.m. 

Then, because I still haven’t eaten, I could walk for an hour with my friend without my blood sugar really fluctuating much at all. If anything, it might start to rise again because the liver will release more glycogen, to convert into glucose, to use as fuel because I still haven’t fed it calories. (Read more about intermittent fasting with type 1 diabetes.)

A 60-minute weightlifting workout before eating breakfast 

It’s 6 a.m. and I’m headed to the gym to lift weights (anaerobic) starting at 6:30 a.m.

If my blood sugar was 110 mg/dL and I headed straight to the gym, I would definitely be 250 mg/dL by the end of that weightlifting workout. This is the result of two issues: dawn phenomenon and the effects of anaerobic exercise explained above.

Instead, I take the entire 1-unit insulin dose which is my normal approach to managing dawn phenomenon because I’m adding anaerobic exercise to the dawn phenomenon! This is a double-whammy of glucose being produced by my body, all on its own, without food.

This is what works for my body

I learned this approach to treatment by studying human physiology and combining it with studying my body’s own insulin needs.

Take good notes. Always keep fast-acting glucose within reach in case you do go low. And try to control as many variables as you can. Exercising with type 1 diabetes is complicated, but if you can figure out the basics of physiology, you can make it much more manageable.