Intermittent Fasting for Type 2 Diabetes: What You Need To Know

In 1915, Dr. Frederick Allen and Dr. Elliot Joselin began using therapeutic fasting to treat patients with diabetes.[*] They had success, but their efforts were soon displaced (and forgotten) with the introduction of supplemental insulin in 1921. 

After nearly a century, science is back on track. We now have promising (if not preliminary) evidence that intermittent fasting may treat type 2 diabetes.[*][*][*] 

So, why does fasting help with diabetes? What are the risks? And how can you get started?

We’ll answer all these questions shortly, but first, let’s cover some background.

Intermittent Fasting 101

If you want to practice intermittent fasting (IF) or time-restricted eating, you need only take regular breaks from calories. These breaks can last anywhere from 12 to 36 hours—anything longer is generally considered an extended fast. 

The breaks don’t need to be zero-calorie breaks. For example, many IF protocols—like 5:2 and ADF (alternate-day fasting)—allow for limited calories on fasting days. 

If you’re following a common protocol like 16:8, you’re eating in an 8-hour window (i.e. 12-8PM) and fasting for 16 hours overnight. Fasting can be as simple as skipping breakfast! Outside of that eating window, it’s okay to consume very low calorie liquids like black coffee, black/herbal tea, water, and broth.

The goal of intermittent fasting isn’t to maximally limit calories but to get you burning body fat for energy. And the key to burning fat is the suppression of insulin.[*] 

When you don’t eat food (or eat a Keto diet), the hormone insulin gets a break from managing your blood sugar. The good news: this low insulin state may promote fat loss, more stable energy, better cognition, and many other health benefits. This is most noticeable in folks with type 2 diabetes, a condition marked by high insulin levels.

The Type 2 Diabetes Crisis

Type 2 diabetes is a metabolic disorder defined by high blood sugar, high insulin, high triglycerides, high blood pressure, and high waist circumference.[*] People with type 2 diabetes are at higher risk for most chronic diseases, with heart disease topping the list. 

We’re in the middle of a diabetes health crisis. Over 10% of people have diabetes in the US, and more than 1 in 3 adults (93 million Americans) are prediabetic.[*] These figures were about seven times lower in the 1950s.[*][*]

What’s driving the shift? Genes haven’t changed, but diets and lifestyles have. We’re moving less and eating more processed foods than ever before.   

Sugar is a big offender. The average American consumes the equivalent of 17 teaspoons per day![*]

By consuming empty carbs, blood sugar stays high, and insulin must stay high to clean it up. Chronically elevated glucose and insulin basically puts your body into a permanent fat-storage mode, and it’s why so many folks stay obese and diabetic. 

What Effect Does Intermittent Fasting Have on Diabetes?

When you eat less frequently, you give your metabolism a break. This allows blood sugar and insulin levels to fall—and fat to be burned—both primary goals of diabetes therapy. 

Much of this effect may be due to calorie restriction. Although intermittent fasting doesn’t always demand you cut calories, it often happens naturally. Less snack time means less food down the gullet, and less food causes a smaller spike in blood sugar and insulin levels. 

In one 2018 study, researchers looked at continuous vs. intermittent calorie restriction in 137 people with type 2 diabetes.[*] Both groups saw significant reductions in HbA1C, an average blood sugar metric used to assess diabetes risk. 

The problem with continuous calorie restriction is that you’re always hungry (probably cold and tired too.) Intermittent fasting helps circumvent this problem by letting you eat your fill, then fast, then eat your fill, and so on. It’s more sustainable. 

Can Intermittent Fasting Treat Diabetes?

The evidence for IF treating type 2 diabetes is promising but preliminary. Let’s review a few data points:

• A 2021 review looked at seven randomized controlled trials using IF to treat type 2 diabetes. Compared to a regular eating program, IF was associated with greater weight loss but reductions in blood sugar were not observed.[*] 
• A 2018 study found that 5:2 intermittent fasting led to significant blood sugar reductions in people with type 2 diabetes.[*] 
• A 2018 review of four studies found that IF was effective for weight loss irrespective of BMI.[*]
• Dr. Jason Fung has successfully treated diabetes with therapeutic fasting in his Toronto clinic.[*] 

Fasting may also help with other forms of diabetes:

• Researchers believe that time-restricted feeding (eating within a compressed daily window) may effectively prevent type 2 diabetes and prediabetes, but more research is needed.[*] 
• Intermittent fasting led to significant weight loss in women with a history of gestational diabetes.[*]
• People with type 1 diabetes fasted safely during Ramadan with proper glucose monitoring.[*] 

Let’s talk more about IF risks now. 

Risks of IF for Diabetes

People with diabetes often take medications (insulin, metformin, etc.) to lower their blood sugar. Doctors generally prescribe these medications in the context of a standard diet. 

Intermittent fasting also lowers blood sugar. So when you combine IF with diabetes medications, you run the risk of pushing blood sugar too low. 

This dangerous condition (hypoglycemia) is the leading risk for people with diabetes practicing IF.[*] The symptoms include fatigue, shakiness, sweating, irregular heartbeat, hunger, irritability, and—in severe cases—death. 

That’s why it’s crucial to seek out medical guidance before fasting with diabetes. Your clinician will likely adjust the drug regimen to minimize hypoglycemia risk. 

Furthermore, any individuals who are pregnant, breastfeeding, currently undergoing chemotherapy, or have a history of disordered eating should consult their physician before starting any intermittent fasting or time-restricted eating protocol.

How To Get Started With IF

Getting started with IF can be as simple as committing to a daily overnight fast. (Even a 12 or 13-hour fast has some metabolic benefits.) From there, you can work your way up to longer fasts if you like. 

Want to make your fasting journey as smooth as possible? Carb Manager premium helps you:

• Know whether it’s time to fast or feast with the daily fasting widget
• Count down the seconds to your next meal with the intermittent fasting timer
• Understand and crush science-backed fasting programs like 16:8, 5:2, OMAD, and others with our extensive article library
• Create a custom IF program to suit your needs and health goals. 
• Track nutrition and fasting simultaneously, all in one app

Using Carb Manager is like transporting yourself to the future. And as science continues to march on, the future of IF for diabetes looks bright.