Fasting and Diabetes

Learn about fasting safely with diabetes.

Research shows fasting offers many health benefits in both humans and animals. A fast is simply a period of time in which you don’t consume any food. There are variations of this definition based on the type of fast you’re doing.

Different variations of fasting include:

  1. Water Fasting: Only water is permitted
  2. Liquid Fasting: Certain liquids, such as tea, coffee, or bone broth, are allowed
  3. Juice Fasting: Vegetable or Fruit Juices are allowed
  4. Partial Fasting: Certain foods are eliminated, such as processed foods, meat, or caffeine
  5. Calorie Restriction: Not a true fast, but restricting calories on certain days

Fasting can lead to an electrolyte imbalance and needs to be done with caution. If at any point you aren’t feeling well, stop fasting. If implementing an extended fast, be sure to talk to your doctor and refeed. Refeeding is an intentional process in which certain types and amounts of food are reintroduced into your diet slowly to avoid serious health complications.

You should not fast if you are pregnant, breastfeeding, under the age of 20, have type 1 diabetes, or have an eating disorder.

History of Fasting

Hippocrates, the father of medicine, image from a sculpture.Fasting has been intentionally applied for therapeutic reasons since about 500 BC. Hippocrates, a Greek physician known as “The Father of Medicine,” has approximately 60 medical documents tied to his name. “Let food be thy medicine and medicine be thy food” is one of his most famous quotes. In respect to fasting, he also said, “To eat when you are sick is to feed your illness.” Humans and animals alike do not eat when they are sick. This temporary fast helps the body to heal and recover.

When thinking about the very nature of fasting, there is no original point of origin. Early humans would often go days without any food. If the body were to become less alert and less able to perform at a high level, humans would have starved when unable to find food. However, the opposite is true when looking at how the body functions during a fasting period.

Health Benefits of Fasting

Fasting has many health benefits. Here are some of those benefits:

Changes the Functions of Hormones, Cells, and Genes

When fasting, your body will undergo many healthy changes. For example, your body will change hormone levels to make stored body fat more accessible, which in turn initiates very important cellular repair processes.

Insulin levels drop significantly, which promotes the body burning fat. Human growth hormone (HGH) levels may increase, which facilitates fat burning and muscle gain. Wastes are removed from cells, improving the efficiency and effectiveness of important cellular repair processes. Many beneficial changes in genes and molecules that occur when fasting are believed to extend life expectancy and help protect you from disease.

Helps Control Blood Sugar Levels

Studies show that people with prediabetes and type 2 diabetes who use intermittent fasting significantly reduce blood sugar levels. Because type 2 diabetes is a metabolic disease where insulin resistance is the primary concern, fasting can help reduce insulin resistance. This, in turn, can increase your body’s sensitivity to insulin. Insulin sensitivity allows your body to use insulin much more efficiently when transporting glucose from your bloodstream to your cells.

As a result, more steady blood sugar levels are often experienced. Dramatic blood sugar spikes and crashes can be prevented with fasting if done correctly. If diagnosed with prediabetes or type 2 diabetes and you want to consider fasting, be sure to consult with your doctor to ensure that your fast is done safely.

Fights Inflammation

Inflammation has several health consequences: heart disease, cancer, multiple sclerosis, depression, Alzheimer’s, and arthritis. Fasting helps reduce inflammation within the body, which also helps protect the body against the aging process.

Fasting reduces the pro-inflammatory cells (monocytes) in blood circulation. These cells go into a deep sleep mode because they aren’t being “fed.”

Protects Your Heart

3D rendered illustration of human body showing the heart and blood vessels.Improves Blood Pressure – Ultra-processed foods, a high-calorie diet, and high-carbohydrate foods contribute to obesity and high blood pressure. Eating a healthy diet and fasting can help reduce insulin. Elevated insulin can accumulate fluid and salt in the body, which increases blood pressure.

Lowers Bad Cholesterol and Triglycerides – A poor diet can lead to high cholesterol. Fasting helps reduce calorie intake, which can lower your low-density lipoproteins (LDL or bad cholesterol).

Prevents Neurodegenerative Disorders and Depression

Not only does fasting help protect brain health, but intermittent fasting over long periods increases the generation of nerve cells that help enhance cognitive function. In addition, because fasting reduces inflammation, it can also help prevent neurodegenerative disorders, such as Alzheimer’s disease.

Fasting increases levels of a brain hormone called brain-derived neurotrophic factor (BDNF). A deficiency of BDNF can cause depression and other problems in your brain.

Helps with Weight Loss

Fasting helps reduce calorie intake, which can lead to weight loss. Because many fasts include healthy foods during eating windows, a change from unhealthy to healthy foods can also aid in weight loss.

Neurotransmitter norepinephrine levels may increase due to a boost in your body’s metabolism. This boost in metabolism can enhance weight loss. Fasting is typically more effective at weight loss than is calorie restriction.

Helps with Muscle Strength

Human growth hormone (HGH) is a protein hormone that is a primary aspect of health. The hormone helps with growth, metabolism, weight loss, and muscle strength. Fasting increases levels of HGH.

Delays Aging and Extends Life Expectancy

Not only can fasting help improve your quality of life as you age, but it can also extend your life expectancy. Because fasting helps eliminate or reduce the effectiveness of the pro-inflammatory cells (monocytes), serious health complications are less likely to occur, which also helps extend and increase the quality of life.

Reduces the Risk of Cancer and Aids with Chemotherapy

Exposing cancer cells to several cycles of fasting can be as effective as chemotherapy in delaying tumor growth and increasing the effectiveness of chemotherapy drugs on cancer patients. Fasting by cancer patients undergoing chemotherapy can lead to a higher tolerance to chemotherapy, fewer side effects, and increased energy levels.

How Fasting Affects Diabetes

Graph showing blood sugar readings during and after eating.Type 2 diabetes patients can experience significant health gains from both intermittent fasting and extended fasting. Not only do patients lower their blood sugar, but they also lose weight.

When you have type 2 diabetes, your insulin resistance is high, which results in your pancreas making more insulin. The more insulin the pancreas creates, the more resistant your cells become to insulin. Fasting improves glucose (sugar) sensitivity, which means that your cells respond better to insulin. The more sensitive your cells are to insulin, the less resistant they are to insulin. As a result, the pancreas makes less insulin, improving your overall blood sugar levels.

Fasting can have significant health benefits for people with prediabetes and type 2 diabetes. If you have type 1 diabetes, LADA, or another less common type of diabetes, fasting can be dangerous because your body produces little to no insulin. Fasting can lead to dangerously low or high blood sugar if not carefully monitored. Please consult your doctor before starting any fast.

Cautions for Fasting

Who Shouldn’t Fast?

You should not fast if you are:

  • Pregnant
  • Breastfeeding
  • Under the age of 20
  • Have type 1 diabetes
  • Have an eating disorder.

Before considering a fast, Total Diabetes Wellness recommends asking your doctor about potential health concerns of implementing a fast.

Nutrients While Fasting

Electrolyte imbalance can occur when you don’t receive proper nutrients during a fast. Electrolyte imbalance usually results from not staying hydrated during your fast, fasting too long, or training too intensely on your fast. Malnutrition can also occur, causing imbalances in essential nutrients your body needs to remain in a healthy state.

Ending an Extended Fast

Many people are unaware of a refeeding process that needs to occur when ending an extended fast. Refeeding syndrome is one of the most severe complications that can result from extended fasting. Fortunately, it is a rare complication. Refeeding syndrome is the “potentially fatal shifts in fluids and electrolytes that may occur in malnourished patients receiving artificial refeeding.” The longer you fast, the more critical this process becomes.

Types of Fasting

Intermittent fasting is fasting during certain hours of the day or certain days of the week. Extended fasting is fasting for 36 hours or longer.

Intermittent Fasting (16:8, 5:2, 4:3)

There are two main types of intermittent fasting. In one method, you are fasting for certain hours of the day. The two numbers used in these fasts will add up to 24 since there are 24 hours in a day. An example is a 16:8 fast. In the other method, you are fasting for certain days of the week. The two numbers used in these fasts will add up to 7 since there are seven days in a week. An example is a 5:2 or 4:3 fast.

A 16:8 fast refers to fasting for 16 hours (typically from dinner to early lunch) and eating during an 8-hour window during the day. Under this regiment, you have an 8-hour window in which you can eat. Be sure not to overeat during these 8 hours. Some people will eat just two meals (one meal at the beginning of the 8-hour eating window and the second meal at the end. Others may eat three times in that 8-hour window, such as three light meals or two meals with a snack in between.

A 4:3 fast refers to eating 4 days out of the week and fasting for 24 hours (1 day) for 3 days of the week. Fasts are typically completed on alternating days. For example, you would eat on Monday, Wednesday, Friday, and Sunday, while fasting on Tuesday, Thursday, and Saturday.

A 5:2 fast refers to eating 5 days out of the week and fasting for 24 hours (1 day) for 2 days of the week. Fasts are typically not done back to back but rather during two days out of the week. This fasting schedule allows more flexibility than the 4:3 fasting schedule.

Intermittent fasting 16:8 showing eating and fasting windows of when to eat.

There isn’t a best way to fast or a best fast. You could implement one fasting method one week and then implement another type of fasting the following week. Mixing up things is important for your body, as the body tends to resist change. Maintaining a stable (homeostasis) and relatively stable internal environment is important to the body.

The best fast is the fast that works the best for your schedule and is sustainable for you.

Homeostasis causes your body to plateau in making gains. This includes weight loss, muscular gains, and insulin resistance. For example, if you’re not making desired gains, try a different fasting schedule or eliminate fasting for a while. If weight loss is no longer taking place, consider changing your macros in your diet.

Extended Fasting

Extended fasting switches your body from a sugar-burning state to a fat-burning state. The longer you fast, the more likely you are to reduce the effects of pro-inflammatory cells (monocytes) in blood circulation.

Although a 36 hour fast is on the shorter side of an extended fast, an extended fast typically becomes easier after the 48-hour mark. This is because of how your body adapts to the fast.

When implementing an extended fast, talk to your doctor to ensure that the fast is done safely. If fasting for 7 days or more, be sure to plan and implement safe refeeding when ending the fast.

Tips for Fasting

Tips for intermittent fasting with diabetes.

  1. Be prepared. – Make sure to consider all aspects of your fast, such as hydration, electrolytes, exercise, length, and refeeding.
  2. Stay hydrated. – Be sure to drink plenty of fluids during your fast, such as water, tea, black coffee, and bone broth.
  3. Plan your last meal. – Eating an unhealthy meal before starting your fast will make the fast more difficult. Choosing a meal that is high in fat will help in feeling full for a longer period when starting your fast.
  4. Track the fast. – Track both the time of your fast and key health metrics throughout your fast. Consider getting an app to help track these metrics.
  5. Track ketones and blood sugar levels. – The longer you fast, the more you need to be aware of your ketone and blood sugar levels. Ketone levels will rise, and blood sugar levels will fall. So be sure to keep them in a healthy range.
  6. Get through the hunger. – Hunger will come and go during your fast and typically is the worst during the second day (24-48 hour mark) of your fast. Keep yourself busy during times of hunger and get through the periods of hunger. The feeling of being hungry will subside.
  7. Fast with others. – Surround yourself with either people who also fast or are sensitive to your fasting schedule. Fasting with others helps with motivation and accountability.
  8. Listen to your body. – It is important to listen to your body while on a fast and ending your fast if you start to feel unwell. For example, feeling weaker than usual, being unable to concentrate, and/or feeling sick are all reasons to end your fast.
  9. Plan your first meal. – Use the length of your fast to determine an appropriate meal or starting point when reintroducing food to the body.

The Bottom Line

Fasting is proven to have significant health benefits. A combination of intermittent and extended fasts can help address multiple health concerns. Be sure to talk to your doctor before fasting. Don’t fast if you are pregnant, breastfeeding, under the age of 20, have type 1 diabetes, or have an eating disorder.

Fasting can help in losing weight, controlling blood sugar levels, and improving metabolism. For people with type 2 diabetes, fasting can help improve insulin sensitivity and reduce or eliminate the need for medication. Always talk to your doctor before starting a fast, ESPECIALLY if you are taking any medications.

It may be helpful to practice fasting by starting with a shorter length fast before you try a longer fast. If you begin to feel sick or have health concerns at any time during your fast, stop the fast and try again later.