Intermittent fasting is an eating pattern that involves periods of voluntary fasting. Several methods exist, each with various time frames for fasting and eating. Intermittent fasting may benefit people with type 2 diabetes.
Many people believe that intermittent fasting can aid weight loss and offer other health benefits.
This article examines whether this eating pattern might benefit people with type 2 diabetes.
Intermittent fasting is an eating regimen that cycles between periods of eating and voluntary fasting or very low calorie intake. Researchers believe intermittent fasting leads to a metabolic switch from using glucose as the primary energy source to using fat.
Intermittent fasting can also positively affect the circadian rhythms of gut biology and the release of insulin and growth hormone. In this way, it can improve energy metabolism and weight regulation.
Intermittent fasting methods involve fasting for different periods:
Time-restricted feeding
This involves eating within a particular time frame each day. A popular plan is the 16:8 method, which requires a person to fast for 16 hours and eat during an 8-hour window.
Alternate-day fasting
People following this pattern alternate between a “fast day,” when they consume no or minimal calories (up to 500), and a feasting day when they can eat as much as they want.
Periodic fasting
This type of fasting involves no or minimal calorie intake for 24-hour periods. Examples are the 5:2 diet and Eat Stop Eat.
With the 5:2 method, a person eats as they typically would on 5 days of the week and then eats about 500 calories during each of the two fasting days, which should not be consecutive.
The Eat Stop Eat regimen requires people to refrain from consuming food and calorie-containing drinks for 24 hours once or twice per week. However, on the other days of the week, it is important they follow a nutritious, balanced diet containing food from all five food groups rather than treating them as feast days.
Learn about other ways to do intermittent fasting.
Intermittent fasting can have various
- promoting weight loss
- improving insulin sensitivity, thus leading to lower insulin requirements
- normalizing fasting blood glucose levels
- reducing hemoglobin A1c levels
Many people with type 2 diabetes also have metabolic syndrome, high blood pressure, or hyperlipidemia (high cholesterol). Intermittent fasting may improve these metabolic markers.
Learn about what foods to avoid with type 2 diabetes.
When a person is fasting, their blood glucose levels decrease. This triggers the pancreas to make and release more glucagon, a hormone that keeps glucose from dropping too low.
Glucagon does this by causing the liver to break down glycogen (stored glucose) and release the glucose back into the bloodstream. Glucagon also stops the liver from taking in and storing glucose, so more glucose stays in the blood.
A feedback system lets the body know when no more glucagon is needed. When everything works correctly, the body will produce insulin to move glucose out of the blood and into the cells to rebalance the increased glucose levels.
However, in someone with diabetes, the pancreas does not make enough insulin, or the body does not use insulin effectively. As a result, the increased levels of glucose stay in the bloodstream.
Read more about how insulin and glucagon regulate blood sugar.
Most research has involved animals rather than humans. The evidence to support health improvements in people is promising, but many of the clinical studies to date have been relatively short-term interventions over a period of months.
A 2018 review article stated that nearly all intermittent fasting studies resulted in some degree of weight loss, ranging from
The use of an intermittent fasting diet may also benefit blood pressure. In one
In a
They concluded that intermittent fasting can help with weight loss and improve specific cardiometabolic health markers, such as fasting glucose and total cholesterol. It may also lead to a reduction in body weight and BMI when compared to calorie restriction.
Scientists know that insulin resistance improves with calorie restriction. After a period of fasting, insulin sensitivity increases, and insulin levels decrease. These changes result in improved blood sugar levels both during fasting and shortly after eating.
Learn about some of the benefits of intermittent fasting.
Intermittent fasting can cause various side effects in people with type 2 diabetes, such as:
- dizziness
- nausea
- insomnia
- syncope (fainting)
- falls
- migraine
- weakness that limits daily activities
- excessive hunger pangs
There is also a
Dehydration is another potential risk of intermittent fasting. Even though a person can consume calorie-free liquids on “fasting days,” it is essential they drink additional fluids to avoid dehydration.
Dehydration can then lead to hypotension (low blood pressure). People may need to reduce or completely stop some medications on fasting days. These include diuretics, antihypertensives, and diabetes medications that can lead to dehydration, such as SGLT-2 inhibitors.
However, it is essential never to stop taking a medication or change the dosage without speaking with a doctor first.
In one small case series, three males reversed their insulin resistance with intermittent fasting. They managed their blood sugar levels after ceasing insulin therapy, experienced weight loss, a reduction in waist circumference, and a decrease in hemoglobin A1c levels.
However, because relapse of diabetes is a possibility, it is more accurate to say that these individuals are in remission.
In a Diabetes Remission Clinical Trial (DiRECT), researchers randomized participants into one of two groups: weight management and pharmacological therapy. They found that
Still, the research is limited, and further studies are necessary.
Learn more about diabetes and weight loss.
Intermittent fasting may worsen symptoms in people with hard-to-regulate blood sugar levels and in those with labile diabetes, which some may also refer to as brittle diabetes.
Minimal research exists on the effects of intermittent fasting in certain populations, such as pregnant or lactating women.
People at higher risk of developing side effects, such as low blood sugar, dehydration, and high blood pressure, should also avoid intermittent fasting. This category includes older adults, people with compromised immune systems, and those with a history of traumatic brain injury or dementia.
Deliberately engaging in fasting can also worsen the challenges that people with eating disorders face.
Learn more about different types of eating disorders.
A person with diabetes should consult their doctor before starting intermittent fasting to ensure that it is safe for them. A person will also need their doctor’s guidance on adjusting the dosages and timing of their medications to reduce the risk of low blood sugar.
Individuals trying intermittent fasting should check their blood sugars more frequently — ideally, every 2 to 4 hours — especially at first.
People with hypoglycemia should break their fast immediately and treat their low blood sugar with 15 grams (g) of carbohydrates in the form of glucose tablets or gels. It is essential to consult a doctor before restarting the fast.
Drinking additional fluids during the fasting period is also important to reduce the risk of dehydration and hypotension. A doctor may recommend stopping or reducing the dose of some diabetes medications, diuretics, and antihypertensives.
People should eat a balanced diet on nonfasting days and avoid processed, fatty, and sugary foods. Doing so will maintain the positive effects of the fasting days.
Read about what you can and cannot consume while fasting.
There are a few diet takeaways from the science of intermittent fasting. Insulin sensitivity changes with a circadian rhythm, decreasing throughout the day and night. Therefore, meals that a person consumes at night are associated with higher glucose and insulin levels.
Limiting the hours of eating to a time earlier in the day — for example, selecting an 8-hour window between 7 a.m. and 3 p.m. or even 10 a.m. and 6 p.m. — may effectively boost metabolism and aid in weight loss.
People should also try to avoid eating and snacking shortly before going to bed. Not snacking between meals will facilitate the metabolic switch from using glucose for energy to using fat.
A balanced diet is also important. People should avoid excessive consumption of sugars and processed carbohydrates, focusing instead on fruits, vegetables, whole grains, lean meat, and healthy fats.
However, the most important factor is that people choose an eating plan they can sustain long term.
Learn about 10 ways to lose weight successfully.
Intermittent fasting involves periods of not eating or drinking beverages with calories. Intermittent fasting can help with weight loss and reducing BMI in people with type 2 diabetes. It can also improve blood glucose levels and total cholesterol.
Intermittent fasting can carry some risks, so a person must talk with their doctor about how to try it safely.
