Intermittent Fasting and Blood Sugar

intermittent fasting blood sugar
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Eat all you want one day, and cut back the next? Intermittent fasting is all the rage, but what about your blood sugar? If you’ve wanted to try fasting but already have concerns about your glucose levels, you might be hesitant to give it a try. So, what controls your blood sugar, and how does fasting affect it?

When your blood sugar levels are high, your pancreas releases the hormone insulin, which removes the glucose from your bloodstream and sends it to your liver to be stored. If your glucose levels stay elevated, your pancreas can’t produce enough insulin to keep up, and that can cause a whole host of health issues, including Type 2 diabetes.

Long-term elevated blood sugar can also induce atherosclerosis or the hardening of your arteries. When your blood vessels, like your arteries, get damaged, you may experience a heart attack, stroke, kidney failure, nerve damage, blindness, poor circulation, or the inability to heal your wounds. 

Fortunately, there’s scientific evidence to suggest that intermittent fasting is a useful tool in the fight against chronically elevated blood sugar. 

Intermittent Fasting Reduces Blood Sugar 

intermittent fasting and high blood sugar

The benefits of intermittent fasting extend far beyond weight loss. Studies show it can reduce your risk for type 2 diabetes and heart disease because it improves the regulation of your blood sugar, increases your resistance to stress, and suppresses inflammation.

A case study published in the US National Library of Medicine showed patients with type 2 diabetes who participated in an intermittent fasting protocol lost weight and managed to stop insulin therapy. In studies where weight loss didn’t occur, fasting still improved the glucose levels of participants. 

This latter finding is significant because it confirms that a reduction in bloodstream glucose is not a secondary benefit of weight loss, but a direct result of intermittent fasting. This reduction in blood sugar could be due to the changes in signaling pathways and metabolic rhythm that fasting invokes, as well as an increase in ketones. 

Improvements in blood sugar tend to be dependent on fasting. Your blood sugar will typically improve after 2-4 weeks of compliance with a fasting protocol, and it dissipates if you return to eating three meals or more per day. 

You may be able to maintain your weight loss after you stop fasting, but long-term fasting is recommended if you need to continue to regulate your blood sugar. If you are not sure what fasting plan is best for you, check out our quiz and find out.

Studies on Blood Sugar and Fasting

Not all studies show that intermittent fasting is a magic wand when it comes to reducing your blood sugar levels. Research indicates daily caloric restriction and diets that mimic fasting also have a positive effect on blood glucose levels.

A 12-month study that compared alternate-day fasting to daily caloric restriction found both methods of calorie reduction lowered fasting glucose levels. Other studies also support the theory that it’s the caloric restriction that reduces fasting glucose and the risk for atherosclerosis. 

However, intermittent fasting may still be among the easiest ways to restrict your caloric intake. You may find it’s easier to limit your calories for a few hours or a few days per week versus every day. 

If you already have insulin resistance, or if your intermittent fasting protocol causes you to stress, fasting can cause an increase in your blood sugar. 

A Brazilian study suggests the stress of fasting might increase the production of free radicals. These stress-induced free radicals can harm the cells in your pancreas, which is the organ responsible for insulin production. Damage to your pancreas can inhibit your ability to reduce glucose in your bloodstream and can lead to an increase in your belly fat. The Brazilian study, however, is an outlier. 

It’s possible that in the Brazilian study, stress increased as a result of excess nourishment on the non-fasting days. Fluctuating blood glucose levels can also increase oxidative stress. One of the reasons why it’s crucial for you to maintain a healthy diet while your fasting is to avoid a blood sugar yo-yo effect. 

Most studies connect intermittent fasting to stress reduction, and to improve cardiovascular health. A study published in Cell Metabolism demonstrates intermittent fasting decreases your oxidative stress and improves your insulin sensitivity. 

How to Control Blood Sugar with Intermittent Fasting

intermittent fasting effect on blood sugar

If you’d like to try intermittent fasting for blood sugar control, there are a few things for you to consider, especially if you have diabetes.

Choose an intermittent fasting plan that won’t cause you stress. During your fast, your insulin levels decrease. In response, your body releases hormones from your liver, one of which is the stress hormone, cortisol. Cortisol tells the liver to release more glucose. So if you’re in a state of stress, or if you have diabetes, your liver is more likely to over-react and release more glucose than you need. As a result,  your blood sugar levels will increase.

If you’re your blood sugar goes up, and you haven’t eaten, it’s likely your liver release glucose into your bloodstream. Exercise is a vital way to utilize sugar in your blood and help your body return to a fat-burning state. 

It’s uncommon, but fasting can cause you to experience hypoglycemia or low blood sugar. If you have diabetes, this can potentially be dangerous since diabetes medications already put you at risk for low blood sugar. Talk to your doctor about your intent to start a fast, especially if you’re on diabetes medications. It’s possible for you to fast safely when your doctor manages your diabetes medications appropriately.

There’s ample evidence intermittent fasting can improve your insulin sensitivity and decrease your fasting glucose levels. These findings are significant since low blood sugar is vital to reduce your risk of cardiovascular disease and diabetes and for more excellent long-term health.

Author's bio


Sara-Mai Conway

Sara-Mai is a writer who specializes in physical and mental health, nutrition, and fitness. She has 20 years of professional experience in the health and wellness industry and is a certified yoga instructor.