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What Is Intermittent Fasting and Is It Right for You?

For many of us, our lives revolve around certain hours of the day, such as work hours, happy hours and sleep hours. But have you heard of eating hours?

You may not have heard it mentioned quite like this but limiting your mealtimes to certain hours of the day is a growing trend known as intermittent fasting. Some people swear by this eating pattern, finding that it helps their weight and appetite and supports overall health.

Is intermittent fasting all hype or is there some truth to these feeding windows? Read on to better understand intermittent fasting, the most popular types of fasting and the advantages and disadvantages associated with each.

What is intermittent fasting?

Intermittent fasting is when you alternate between periods of eating and not eating each day or week. While the word “fasting” may conjure fears of starvation, it’s usually just a period of time between 12 and 40 hours.

“The belief behind this is that by restricting foods to a small window of time, your body will use up glucose and glycogen (glucose storage in the body) and turn to energy reserves stored in fat,” said Beril Hezer, a registered dietitian at Banner Health. “Glucose requires insulin to enter our cells. Between meals, insulin levels start to decrease, which causes fat cells to release energy. The idea of intermittent fasting is to allow the insulin levels to decrease far and long enough to burn fat.”

Types of intermittent fasting

How does intermittent fasting work? There are several ways you can go about intermittent fasting—it just comes down to your personal preference. Some popular approaches and forms of intermittent fasting include:

Daily time restrictions (16/8 or 14/10)

Since most of us “fast” in our sleep, this method is popular. You eat a normal diet within an 8-hour window or 10-hour window each day. This can be done every day or even once or twice a week—whatever you prefer.

“For example, if you finish dinner at 6 p.m. on Tuesday, you won’t eat again until 10 a.m. or 8 a.m. Wednesday,” Hezer said.

Twice a week method (5:2)

You eat a normal diet five days a week and fast and eat roughly 500 calories for two days. You can choose which two days you want to fast, either consecutively or on different days.

Alternate day fasting

You eat normally one day and fast the next day, alternating between the two during the week. You can completely fast or eat roughly 500 calories on your fasting days.

Eat stop eat method

You fast for a complete 24 hours one to two times a week, such as breakfast to breakfast, then eat normally on your non-fasting days. This method is the most extreme and may be difficult to maintain long term or if you’re new to fasting.

Besides feeling pangs of hunger, fasting can have side effects, including headaches, insomnia, fatigue, nausea and changes to your overall mood.

“Low blood and brain glucose levels are associated with a poor mood,” Hezer said. “Irritability and anxiety are classic symptoms of low blood sugar levels. Prolonged fasting can cause significant hormonal changes as well.”

Benefits of intermittent fasting

Research shows that intermittent fasting periods do more than burn fat. There is a range of other health benefits associated with this practice. Intermittent fasting can help you lose weight because it may help you eat less overall, as well as protect against chronic diseases.

“Studies have shown that alternate fasting over 8 to 12 weeks decreases LDL (low density lipoprotein), or bad cholesterol, and total cholesterol, as well as triglycerides in normal weight, overweight and obese people,” Hezer said. “It can also improve blood sugar levels and decrease inflammation, which are two big contributors to heart disease and diabetes.”

Intermittent fasting isn’t right for everyone

Skipping meals may not be the best for those taking certain medications or who have certain conditions. You should talk to your health care provider or a registered dietitian before starting intermittent fasting, especially if you’re pregnant or breastfeeding, have a history of eating disorders, have diabetes or blood sugar problems, are taking certain medications, like NSAIDs (nonsteroidal anti-inflammatory drugs), or supplements or are under age 18.

Fasting can also be exhausting. During times of fasting, you may have low energy, not want to go out or be out or feel like you need to rest to conserve your energy.

What should you eat while intermittent fasting?

During times of fasting, it’s recommended you drink water and zero-calorie beverages such as black coffee and tea.

When you are in periods of eating, consume healthy foods and drinks, such as water, fruits, vegetables, whole grains, lean meats, plant proteins and non- or low-fat dairy and products or dairy alternatives.

Avoid things like high-calorie junk foods, fried items, sweet treats and soft drinks.

And remember to listen to your body and focus on mindful eating.

“If you’re used to relying on your intuition to decide when to eat, intermittent fasting might feel unnatural at first,” Hezer said. “Listen for body signals that tell you that you are no longer hungry. Observe the signs that show that you are comfortably full. Pause in the middle of a meal or snack and ask yourself how the food tastes and what your current fullness level is.”


Intermittent fasting is a weight loss tool that works for some but not everyone. Keep in mind that it can have different effects on different people. Talk to your health care provider or a dietitian before starting any new diet. They can review your health history and provide you with guidance.

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