The In’s and Out’s of Intermittent Fasting

Intermittent fasting (IF) continues to have its moment. Click around the internet and you’ll find that it lands in nearly every top diet trends round-up. Albeit popular, it isn’t new.

Fasting is one of the oldest dietary interventions and healing traditions known to us. It’s been part of human culture and religion for thousands of years.

Today, intermittent fasting has arguably helped people lose weight, gain muscle, improve heart health, combat brain fog, and feel healthier overall. Before you try it out, get to know the intermittent fasting basics. Find out what exactly it is, how the various methods differ, if the benefits of intermittent fasting are backed by research, and, most importantly, if it’s right for you.

What Is Intermittent Fasting?

Put simply, IF is strategic occasional starvation. Intermittent fasting calls for cycling through periods of regular eating and fasting. During fasting periods, you either drastically restrict your calorie intake or don’t eat at all.

What Are the Various Types of Intermittent Fasting?

People approach IF in a variety of ways. Think of the following as your intermittent fasting guide.

1. The 16/8 Method

This method is also known as the Leangains method, which was popularized by fitness expert Martin Berkhan—and actor Hugh Jackman reportedly used this method to get in shape for his role as Wolverine in the X-Men films.

Essentially, the 16/8 method involves time-restricted eating: fasting every day for 14 to 16 hours and limiting your daily eating window to 8 to 10 hours. Some people do this by not eating anything after dinner and then skipping breakfast. However, some will still drink water, coffee, and other low-caloric beverages during the fast to stay hydrated and to help mitigate hunger. Some find this method to be the simplest to adopt, especially those who aren’t naturally hungry in the morning and prefer to skip breakfast.

2. The 5:2 Method

British journalist and doctor Michael Mosley is known for using the 5:2 method, aka Fast Diet, which calls for eating normally five days of the week and restricting calories to 500 (for women) and 600 (for men) two days a week. For example, a woman might eat her regular diet every day except Tuesdays and Fridays, when she eats two, small 250-calorie meals.

3. The 24-Hour Method

Fitness expert Brad Pilon developed this method, which is sometimes called Eat-Stop-Eat. It involves a 24-hour fast, either once or twice a week. Whether it’s done from breakfast to breakfast, lunch to lunch, or dinner to dinner, the end game is the same: you don’t eat for a total of 24 hours. Water, coffee, and other non-alcoholic, low-caloric beverages are allowed during the fast. Solid food is not. 

4. The Alternate-Day Method

Just as the name implies, alternate-day fasting means alternating fast days and feed days. Some versions allow 500 calories on fasting days; others don’t. Experts warn that this one isn’t for first-time fasters because some find it difficult to stick to the extremes—one day you’re eating either nothing or next to nothing and the next day you’re eating more than normal amounts.

5. The Warrior Method

Fitness expert and author Ori Hofmekler popularized the Warrior Diet. Essentially, during the day fast, you can eat small amounts of raw fruits and vegetables. At night during a four-hour period, you feast on one large meal that consists of whole, unprocessed foods—similar to those eaten on a paleo diet.

5 Intermittent Fasting Benefits

1. Weight Loss

Because calories are restricted during IF periods, fewer calories are consumed overall, which can cause you to lose weight. Intermittent fasting benefits may include lowering insulin levels, which may propel weight loss. Insulin is a hormone that allows cells to take in glucose. The body breaks down carbohydrates into glucose, which cells either use for energy right away or convert to body fat and store for future use. When you don’t eat, insulin levels drop and that causes cells to release their glucose stores as energy. Regular repetition of this process may result in weight loss.

One clinical trial compared intermittent fasting and a traditional calorie-restriction diet, and the effects both had on weight loss over one year. The result? It was a tie. Researchers determined that both fasting methods were similarly effective in helping participants shed pounds. There also weren’t tremendous differences in other health markers, such as blood pressure and heart rate.   

2. Reduced Risk of Type 2 Diabetes

More than 30 million people in the U.S. have diabetes, and 90 percent to 95 percent of them have type 2 diabetes, according to the Centers for Disease Control and Prevention.

Being overweight or obese is a primary risk factor for developing type 2 diabetes. People with type 2 diabetes experience insulin resistance. In other words, their bodies still produce insulin, but they’re unable to use it effectively.

One study examined whether intermittent fasting can lower insulin levels and blood glucose levels. The researchers found that the evidence was inconclusive and that further research is needed.

Another study looked at three men between the ages of 40 and 67 with type 2 diabetes who tried IF for approximately 10 months. Two of the men fasted every second day for 24 hours. The other fasted for three days a week. On days when the men fasted, they were allowed to drink water and low-calorie drinks such as tea, coffee, and broth. They could also eat a low-calorie meal at night.

All of the men were able to stop insulin treatment within a month. One was able to stop insulin treatment after five days. Dr. Jason Fung, the author of the study and director of the Intensive Dietary Management Program, acknowledged that his study was small and that more research would be needed.

3. Brain Health

Some animal studies show that intermittent fasting improves brain health. One study found that memory and learning were improved in mice that were on brief intermittent fasting diets vs. those that were given unlimited access to food. Other animal studies showed that IF can suppress brain inflammation, which has links to neurological conditions.

Dr. Mark Mattson, a professor of neuroscience at the Johns Hopkins School of Medicine, and his colleagues found that IF may help the brain ward off neurodegenerative diseases like Alzheimer’s and Parkinson’s while also improving memory and mood. How? After glycogen is used up, your body burns fat, which is converted to ketones that are used by neurons as energy. Ketones promote positive changes in the structure of synapses—or connecting points—that affect learning, memory, and overall brain health. However, if you eat three meals a day with snacks between, your body never gets the chance to deplete the glycogen stores and, therefore, ketones aren’t produced. Exercise also influences your body to lower its glycogen levels and has been shown to have the same positive effects on the brain as fasting.

4. Reduced Cancer Risk

A JAMA Oncology study examined the relationship between 2,413 women who were diagnosed with early-stage breast cancer and nightly fasting. Researchers found that women who fasted for fewer than 13 hours a night had a greater risk of breast cancer reoccurring. The researchers acknowledged that fasting for more than 13 hours has benefits because of a correlation between caloric intake and tumor growth. Lower blood sugar levels and reduced inflammation are associated with slowing the growth of some types of tumors.

Because studies have also found a link between obesity and a higher risk for different types of cancers, weight loss that can be associated with IF could help to reduce this risk.

5. Heart Health

Heart disease remains the leading cause of death for men and women in the U.S., according to the Centers for Disease Control and Prevention. The four major risk factors in heart disease are high blood pressure, cholesterol, diabetes, and weight. Fasting can lower blood pressure, heart rate, cholesterol, and triglycerides, which are a kind of fat in the blood that is linked to heart disease.

However, health care practitioners caution that fasting can also lead to an electrolyte imbalance, which can make the heart unstable and prone to arrhythmias, also known as an irregular heartbeat.

Is Intermittent Fasting Healthy for You?

A lot more research needs to be done to determine if intermittent fasting is any healthier than other eating and health practices.

When it comes to weight loss, some people find intermittent fasting easier than other forms of calorie restriction, while others don’t. However, because IF typically focuses on when and how much rather than what to eat, some nutrition experts aren’t on board. After all, not all calories are created equal, and what you eat can also have a significant impact on overall health.

The bottom line: One health regimen does not fit all. If you’re curious about trying IF, ask your health care practitioner to help you design an individualized intermittent fasting plan for you that adds the right foods to both your fasting and non-fasting days to ensure you stay in good health.

*Editor’s Note: The information in this article is intended for your educational use only; does not necessarily reflect the opinions of the Chopra Center's Mind-Body Medical Group; and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition and before undertaking any diet, supplement, fitness, or other health program


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About the Author

Nicole Leatherman

Nutrition Writer and Editor
Nicole believes in the Hippocratic philosophy, “Let food be thy medicine,” and her passion is creating content that helps others learn about self-healing through eating real foods and living an intentionally balanced life. When she isn’t writing or editing, she spends time in the yoga studio, on the mountain trails in Colorado, and in the kitchen creating recipes packed with nutrient-rich foods. She has a bachelor’s degree in journalism, and has been a professional writer and editor for more than 15 years.Read more