Fasting and diabetes: Risks and benefits for people with T1D

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Julie Cunningham, MPH, RDN, CDCES, IBCLC

Though some people with diabetes may not think of voluntarily fasting, others are curious about its possible benefits. There are a number of reasons why someone living with diabetes might choose not to eat or drink for a certain period of time — but fasting and diabetes can be a risky combination if not approached thoughtfully.

If this is something you've been thinking about, we've got you covered! Keep reading to learn more about the potential risks and benefits of fasting with type 1 diabetes.

Common types of fasting

  • Religious: For thousands of years, people all over the world have been fasting for religious reasons. Fasting is considered a traditional way to refocus or regain spirituality in some faiths. Examples include the month-long period of Ramadan, in which Muslims do not eat or drink anything between sunrise and sunset; Yom Kippur, the holiest day on the calendar for people of the Jewish faith (no food or drink is consumed for a 25-hour period); and Lent, a 40-day period when Catholics fast by avoiding meat.
  • Intermittent: People who participate in intermittent fasting limit their food intake to a specific time period during the day (16:8 is the most common schedule, fasting for 16 hours with an 8-hour eating window), but they don't necessarily limit the type of food they eat. This type of fasting is popular among people who want to manage their weight, but can be beneficial for people with diabetes who are simply trying to get better control over their glucose levels.
  • Dietary: Dietary fasting refers to completely avoiding food or severely limiting the number of calories eaten for several days or more. This type of fasting varies based on the end health goal and will look different for everyone. For example, a person who is fasting might not eat at all every other day while eating very few calories (about 500) on the opposite days.
  • Medical: A short-term (24 hours or less) medical fast might be necessary prior to getting blood work done, surgery requiring anesthesia, or before a gastrointestinal procedure such as a colonoscopy.

Health benefits of traditional fasting

While intermittent fasting has been getting more than its fair share of publicity in recent years, traditional fasting — which includes religious, dietary and medical fasting — has been practiced and celebrated for millennia.

When done properly, traditional fasting can provide many benefits, including the following:

  • Improved metabolism.
  • Loss of fat (as opposed to the loss of muscle).
  • Lower blood pressure.
  • Lower LDL levels (which relates to your "bad" cholesterol).
  • Reduced inflammation.
  • Increased insulin sensitivity (this improves your body's ability to use available insulin to process carbohydrates).
  • Improved repair and removal of damaged cells (the scientific name of this process is apoptosis).
  • Changes in gene expression (this relates to the way your body uses its DNA to make protein, which may lead to a longer life).

As you can see, there are numerous health benefits of fasting. More research is being done to determine exactly how fasting causes all of these benefits — with a special focus being put on the connection between fasting and diabetes. For now, it's safe to say that fasting can "reset" many of the body's processes.

Risks of fasting with diabetes

Fatigue, irritability, and headaches are common side effects of fasting that can occur in people with and without diabetes — and are sometimes unpleasant enough to make fasting a short-lived experience. Nutrient deficiency is also a potential risk for anyone who fasts for a significant period of time. Specific to people with diabetes, the main risk of fasting is hypoglycemia (severely low blood sugar).

If you live with type 1 diabetes, hypoglycemia can occur when your carbohydrate intake decreases significantly or drops to none at all. In turn, your need for insulin will drop as well. You may need to decrease (or altogether skip) your mealtime insulin dose, depending on your carbohydrate intake.

People with diabetes will need to discuss their plans for fasting with their healthcare teams to ensure that they have a solid plan for modifying insulin schedules. Blood sugar levels will need to be closely monitored, as fasting can affect individuals differently.

Putting safety first with fasting and diabetes

When living with diabetes, your priority health goal is to keep your blood sugar in range. Generally, that range is about 70-180 mg/dL, depending on whether or not you've eaten and how tightly you want to control your blood glucose.

While fasting, monitoring your blood glucose carefully is just as important as when you're eating regular meals. It's possible that in addition to changing your mealtime insulin dose, you'll also need to change the way you dose your long-acting insulin. In situations like this, continuous glucose monitors can be extremely valuable, as they allow users to review their blood sugar levels in real-time and spot potential trends to take action.

Before deciding to fast, it's best to talk with your healthcare provider. You may also want to get advice from your registered dietitian or certified diabetes educator before deciding whether or not fasting is right for you.

Curious to learn more about the ins and outs of living with diabetes? Useful tips and advice can be found by exploring more on the Edgepark Health Insights blog.

Julie Cunningham, MPH, RDN, CDCES, IBCLC

Julie Cunningham is a Registered Dietitian Nutritionist and a Certified Diabetes Care and Education Specialist. Julie provides online nutrition programs for people who want to end their struggle with diabetes. She can be found at juliecunninghamrd.com and at TameType2.

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