Intermittent Fasting and Diabetes: The Safety and Possible Benefits of Timed Eating

People who practice intermittent fasting (IF) only eat during a small period of time. Outside of this "eating window," they don’t consume any calories. IF is growing in popularity due to its range of potential health benefits, but it’s not safe for everyone.

For example, researchers are still studying its safety and benefits for people with diabetes. Potential benefits may include more stable glucose levels, decreased insulin resistance, and improvements in metabolism. But the American Diabetes Association does not have recommendations for intermittent fasting with diabetes. 

So, if you live with diabetes and are interested in IF, consider reaching out to your care team. Receiving tailored support and guidance will help you meet your goals safely. 

How does intermittent fasting work?

Simply put, IF is focused on “when” you eat rather than “what” you eat. People who follow an IF plan can choose from a few different approaches: 

• They may schedule hours during the day to eat and hours to fast.

• They may alternate between “regular” eating days and “IF” days.

• They may restrict calories during IF “eating windows.”

While the focus is more on “when” you eat than “what” you eat, eating well-balanced and nutritious meals (like in the Mediterranean diet) is encouraged.

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Researchers do not completely understand how IF works in the body. One proposed mechanism is that by fasting regularly, your body switches from using glucose as a fuel source to burning fat stores. This “metabolic switch,” or “metabolic reprogramming,” may affect the hormones involved in regulating metabolism and appetite. 

Evidence shows that IF can help:

• Boost weight loss

• Improve visceral (deep) fat loss

• Lower glucose levels

• Reduce systemic inflammation

• Optimize insulin sensitivity 

IF also has better adherence than traditional calorie-restricted diets, meaning that people are able to stick to it longer term. 

Types of intermittent fasting methods for people with diabetes

Finding a balance between an IF eating plan and your diabetes management plan may be challenging at first. That’s why it’s important to talk with your diabetes care team before you get started. They can help you choose an option that’s best for you and adjust your medications as needed. 

While there are different IF methods, they all have one thing in common — regular time periods to eat and to fast. 

Popular IF examples include:

• Time-restricted feeding: There’s no caloric intake for 12 to 20 hours at a time, then there’s a short period of normal food intake. For example, someone may eat only between 12PM and 8PM and fast during the hours outside this period.

• Alternate-day fasting: There’s no caloric intake for 24 hours every other day, with normal caloric intake on the day in between.

• Eat Stop Eat Method: There’s no caloric intake 1 to 2 days per week. 

• Modified fasting, or the 5:2 diet: There are very low amounts of calorie consumption for a few days per week and then normal food intake on the days in between. For example, someone may consume only 500 to 700 calories on their “fasting” day.

How IF affects your metabolism

Regardless of the method you choose, IF will affect your body’s metabolism. Here’s why. During fasting hours, your body breaks down its fat stores to use as energy. This produces ketones — an alternative source of fuel for the body when sugar (glucose) isn’t available.

During this process, blood glucose levels usually decrease — especially if someone is taking diabetes medications. Without fast treatment, low blood glucose (hypoglycemia) can become a medical emergency. 

That's why having the support of your diabetes care team is the safest approach. They'll help you adjust your diabetes treatment plan along the way. 

What are the benefits of intermittent fasting?

Some studies show that IF can help with weight loss in people with diabetes. These studies compared IF to traditional calorie-restricted diets. An analysis of several studies found that people with Type 2 diabetes lost more weight with IF than with continuous calorie restrictions.

Researchers looked at other measurements in people with diabetes, too. They found that IF also helped improve blood sugar and cholesterol levels. But it was not any better than the classic calorie-restricted diet for these factors.

What are the risks of intermittent fasting for someone with diabetes?

Potential risks of IF for people with diabetes include:

• Hypoglycemia: This is a serious risk. That’s because the brain needs glucose to function. Low blood glucose can cause confusion, lightheadedness, or loss of consciousness.

• Diabetic ketoacidosis (DKA): This is when ketones in the blood rise to unsafe levels. DKA is a life-threatening condition that’s more common in people with Type 1 diabetes. But it can also affect people with Type 2 diabetes.

• Dehydration: People with diabetes have an above average risk of dehydration. This is because high blood glucose levels can cause increased urination. If you drink less fluid and urinate more, your risk of dehydration rises even more. 

People with diabetes may be more susceptible to risks than those who do not have diabetes.

How to safely start intermittent fasting when you have diabetes

Limiting your daily calorie intake or skipping meals altogether can be challenging with diabetes. That’s why it’s important to approach fasting with care. 

If you have diabetes, consider these tips to safely get started with IF:

• Talk with your diabetes care team before starting.

• Know your glucose target range, and follow your diabetes management plan. 

• Check your blood glucose at home more frequently and/or wear a continuous glucose monitor.

• Always treat low blood glucose — even if you are fasting.

• Alert your healthcare provider if you’re having patterns of lows or highs.

• Drink fluids throughout the day to avoid dehydration.

• Adjust your medications as your care team suggests.

• Choose nutritious options during your eating window — it’s not a time to overeat.

• Schedule regular appointments with your healthcare team.

Are there better dietary options for someone with diabetes?

There’s not enough research to say that intermittent fasting is a good option for diabetes. Some studies do show that people with diabetes might lose more weight with IF than a regular calorie-restricted diet.

But IF is not necessarily better for improving blood sugar or cholesterol levels. That’s because other calorie-restricted diets have similar benefits, and they may be safer. Research is mixed on whether this pattern of eating is easier to maintain over the long term than other forms of calorie restriction.

People with diabetes who want to try IF should talk with their healthcare team about the decision. That way, their medications and treatment can be changed to minimize the risks.

Why trust our experts?

Written by:

Joanna Jan, MD

Joanna Jan, MD, is board-certified in internal medicine and licensed to practice medicine in the state of Pennsylvania. In 2017, she received her board certification from the American Board of Internal Medicine.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Jewels Doskicz, RN, BA

Jewels Doskicz, RN, BA, is an Arizona-based registered nurse with 22 years of hospital-wide clinical nursing experience and 11 years of medical writing and editing experience. She was a former healthcare content creator for a digital health tool at HealthLoop and director of clinical content operations at GetWellNetwork.

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