Why does exercise sometimes raise your blood sugar?

The short answer is that your body does what it is designed to do. But the mechanics behind it can be difficult to understand.

The first official directives for a safe exercise have been published in The Lancet reviewed in 2017. And more recently, in 2020, experts published a international position statement on Managing Blood Glucose For Exercise Using Continuous Blood Glucose Monitoring (CGM) In Type 1 Diabetes.

These guidelines note in particular that “weight lifting, sprinting and intense aerobic exercise can promote an increase in blood sugar which can last for hours”, but there is little explanation as to why this occurs. . And overall, the information can be overwhelming and difficult to follow.

So, DiabetesMine turned to several diabetes and exercise experts to help explain what’s going on here.

“It is essential that your brain and nervous system have access to blood sugar at all times. Because of this, the body has redundant hormones that increase blood sugar, like glucagon and adrenaline, ”explained Sheri R. Colberg, PhD, Emeritus Professor of Exercise Science at Old Dominion University in Norfolk, Va., And creator of Diabetesmotion.com. “What happens with exercise is that blood sugar increasing hormones are released to help increase the amount of BG released to match what your active muscles are using.”

Colberg admits, “The system is not perfect, however, and doing strenuous activity causes these hormones to be exaggeratedly released. So when someone is doing strenuous but short activities, blood sugar levels often rise due to the release of too many hormones.

Ginger Vieira, health coach, advocate and author of several diabetes books, used her experience as a competitive power lifter, personal trainer, and Ashtanga yoga instructor to describe the effect of some of the more common mechanisms of glucose spikes during intense exercise: lactic acid, adrenaline and fasting exercise.

Lactic acid. The process of gluconeogenesis converts lactic acid into glucose and recycles this glucose in your muscles for fuel, ”Vieira said. “This is how the body provides fuel to your muscles when you work too hard to circulate oxygen and glucose through your cells like your body would during general aerobics. [cardio] exercise.”

Adrenaline. As often happens when participating in competitive sports, “your body releases adrenaline for that ‘fight or flight’ burst of energy,” Vieira described. “Adrenaline tells your liver to release stored glucose as glycogen to provide the extra fuel it needs for the ‘fight’… or the football game. This can easily spike your blood sugar over 100 points.

Exercise on an empty stomach. Exercising on an empty stomach can cause blood sugar levels to spike, especially right after waking up. This is because exercise can further exaggerate what is called the dawn phenomenon, when early in the morning, “your liver releases glucose stored with morning hormones, to give your brain the fuel it needs to function,” Vieira explained.

Obviously, there are many mechanisms that can cause blood sugar levels to spike during exercise. No wonder, it can be so hard to know what to do to bring blood sugar down.

One of the first things you might ask is if there are “good” and “bad” exercises for people with diabetes… like in “Maybe I should avoid the“ bad ”ones”.

Christel Oerum, certified personal trainer and founder of Strong diabetes and Diabetic gourmet, proposed another way of approaching this question. “Think of it like this: your body just wants to help you, it wants you to be successful. So when you do certain types of workouts, mainly anaerobic exercises, your body is trying to make sure that you have the energy to be successful. It does this by releasing hormones that allow energy, in the form of glucose, to be released into your bloodstream. And it can increase blood sugar.

This response is not unique to people with diabetes. Vieira confirmed that “in a non-diabetic body, the exact same process occurs, but their body produces extra insulin to process the extra glucose.”

“Just because blood sugar rises during certain types of exercise doesn’t mean that it is bad exercise or that the rise is happening for the wrong reason,” Vieira added. “This is the body’s normal reaction to several factors that can occur primarily during anaerobic exercise, such as weight lifting, sprinting, spinning classes, times of competition, etc.”

Since it’s anaerobic exercise that causes blood sugar spikes during activity, you might think that simply avoiding sprints, resistance training, or other anaerobic activities might be the answer.

“But that would be a shame, because resistance training is fantastic for managing diabetes,” Oerum noted. “Most people will see their insulin sensitivity increase later on, and more often than not their blood sugar will drop on its own.”

Oerum suggests combining anaerobic exercise with aerobic exercise. This approach will balance the effects and generally lower blood sugar levels soon after you finish exercising.

Of course, if your exercise goal is to lower your blood sugar immediately, then aerobic exercise like walking, swimming, or skipping rope will be the effective choice.

Ultimately, it is the presence of insulin that determines when and how quickly blood sugar levels drop.

So try to assess the situation in terms of insulin intake, or on-board insulin (IOB). Maybe you didn’t take enough insulin to cover a meal before your workout, or maybe you are exercising soon after waking up when BIO is at its natural low.

Spikes in blood sugar caused by adrenaline rushes can be difficult to anticipate, as they most often occur in the middle of a workout. This means that rather than treating the peak immediately, you will likely have to wait and take extra insulin afterwards.

More insulin is also needed when the spike results from exercise on an empty stomach. Some extra insulin will be needed, but not to the point of causing an episode of hypoglycemia during or after exercise.

Unfortunately, there are no hard and fast rules for making these insulin dosage adjustments. Each situation for each person will require an individualized response. It is best to work with your medical team to determine the best response for you.

That being said, Vieira and Oerum suggest taking notes and tracking your experience so you can learn from it. You may find that for you personally, particular activities have a predictable spike in blood sugar. Over time, you can develop a routine that allows you to both get the exercise you need and anticipate those frustrating peaks.

Many people who wear an insulin pump learn to use personalized “temporary basal” settings to increase (or decrease) background insulin during specific training routines. This can help compensate for the spike so you don’t have to deal with a huge dose of bolus insulin afterwards.

You can also experiment with your own ideal “starting glucose level” before you begin to exercise. The Guidelines 2017 give general recommendations of “at-target” levels of 126 to 180 mg / dL, and to consume 10 to 20 grams of fast-acting glucose before starting. You will need to monitor your own experience to find out what is best for you.

Once you understand why blood sugar levels rise during exercise and accept that this isn’t necessarily a bad thing, you will hopefully notice a mental shift from being frustrated and disappointed to appreciate what. you can do in response.

While there are no one-size-fits-all guidelines, be aware that over time you can create an exercise routine that includes small amounts of glucose and insulin, which helps keep your blood sugar levels down. reasonable.