Intermittent Fasting 101: What You Need to Know Before Starting

By Alex Hoffmann on April, 28 2021
Nutrition
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Alex Hoffmann

Dr. Alex Hoffmann is the President of the College of Exercise Science. He earned a doctorate in Sports Management from the United States Sports Academy, a master's degree in kinesiology from California State University, Fullerton, and a bachelor's degree in exercise science from Central College. Prior to his career in academia, Dr. Hoffmann worked as Master Fitness Trainer course instructor for the United States Army, and as a strength and conditioning coach, personal trainer, and nutritionist.

If you search Google, you’ll find hundreds of “intermittent fasting 101” articles. It’s become more mainstream as a dietary lifestyle, but if you’re new to the practice you may be wondering how it works, if it’s safe, or how long you need to follow the regimen to see results. 

Our intermittent fasting 101 guide breaks down the science of intermittent fasting and how to do it correctly so you can get the most out of this powerful dietary shift. The more you understand upfront, the more empowered you’ll be to make an informed decision about intermittent fasting as part of your nutrition plan.   

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What Is Intermittent Fasting?

The goal of intermittent fasting is to keep your food intake to a specific period of time, not eating for a certain number of hours—or even days—in succession. For instance, the New England Journal of Medicine suggests that you might start by consuming one meal each day within a 6-hour period, then fasting for the remaining 18 hours.

Intermittent fasting teaches you to be mindful of when you eat. The human body functions on a natural circadian rhythm of 24-hour cycles that regulate both the intake and output of energy. Consistent intervals of feeding and fasting work with this circadian rhythm to ensure the body metabolizes nutrients in the most optimal time-frame, explains the Cell Metabolism Journal.  

In other words, intermittent fasting promotes balance and efficiency for your metabolism. When the body is at its peak energy state, a prolonged fast will not only burn off the calories from your last meal, but will also convert existing fat stores into burnable energy. 

Conversely, eating at numerous, frequent and irregular points in the day with no pattern of consistency can throw off circadian rhythms, suggests Cell Metabolism Journal. If that disruption becomes chronic, you can put yourself at an increased risk for metabolic syndrome, insulin resistance, hypertension, inflammation, high cholesterol or obesity.     

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What Are the Potential Health Benefits?

Intermittent fasting provides a wide range of health benefits that may be challenging to experience otherwise. While it’s often used as a way to moderate calories for weight loss, intermittent fasting can also lead to a host of other physical and cognitive benefits too. 

According to the same research from the New England Journal of Medicine, this dietary lifestyle can:

  • Improve working memory
  • Strengthen cardiovascular function
  • Lower oxidative stress markers
  • Reduce inflammation levels
  • Minimize risk of diabetes 
  • Help manage autoimmune symptoms
  • Delay onset of neurodegenerative illness
  • Optimize and protects organs 
  • Boost athletic endurance
  • Increase healthy gut microbiota  
  • Promote cell regeneration
  • Decrease blood pressure
  • Decrease abdominal fat loss
  • Elevate human growth hormone

 

The data goes on to reveal that some of these potential health outcomes are also influenced by other factors such as personal genetics. Meaning, you may not experience all the benefits listed when you start intermittent fasting, but if done correctly—as is explained below—your health and well-being will significantly improve.

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Intermittent Fasting 101: How to Do It

There are four main styles of intermittent fasting and can take some trial and error to determine which method works best for you, explains Anna Taylor, registered dietitian at The Cleveland Clinic. This is not a “one-size-fits-all approach,” she continues, so experiment with the following techniques until you find what meets your goals or preferences.  

 

Twice a Week (5:2) Method

Eat your typical amount of food five days a week and switch to just 500 calories on the other two days. Make sure the two fasting days are non-consecutive, and aim to portion out your 500 calorie allotment into one 200 calorie meal and one 300 calorie meal. Choose nutrient-dense foods with fiber and protein, which will satiate you longer during the fasting periods.  

  

Alternate Day Fasting Method 

The goal is to alternate between eating one day and fasting the next. On fasting days, eat about 25 percent of your regular food intake (not to exceed 500 calories) and resume your regular meals on non-fasting days. For a more rigorous approach, you can also choose not to eat on fasting days—just check with a doctor first to make sure this is a safe option for your health.

 

Time Restricted (16/8 or 14/10) Method

Eat within a certain window of time, then fast for the remaining hours left in the day. There are two common frameworks you can use to practice this method:

  • 16/8: eat for 8 hours, then fast for 16 hours. For example, you might eat from 11am to 7pm or 12pm to 8pm.
  • 14/10: eat for 10 hours, then fast for 14 hours. For example, you might eat from 10am to 8pm. 

 

24-Hour Fast (Stop-Eat-Stop) Method

Restrict food intake entirely for a full 24 hours once or twice a week. On non-fasting days, eat your regular amount of food at standard intervals. Side-effects on fasting days can be painful or uncomfortable until the body acclimates, including headaches, fatigue, irritable mood, or lack of energy, so this approach should be used while working with a health professional.

 

Are There Any Risks to Be Aware Of?

While there are clear benefits to intermittent fasting, this practice is not healthy or safe for everyone. Certain groups of people should not attempt this unless under clinical supervision, explains Christie Williams, registered dietitian at Johns Hopkins Medicine. She recommends the following individuals refrain from intermittent fasting:

  • Children under the age of 18
  • People who already have diabetes
  • Women who are pregnant or breastfeeding 
  • People with a history of eating disorders

Whether you fall into one of these categories or not, it’s still a smart idea to talk about this with a health professional before starting. The goal is to create a sustainable, effective plan that aligns with your specific wellness needs.    

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Intermittent Fasting Could be for You

Intermittent fasting may be the missing piece you’ve been looking for to take your healthy journey to the next level. Our intermittent fasting 101 guide is meant to inform and educate, but we ask that you always consult with a health professional before restricting food intake for any period of time. With the right support and tools, intermittent fasting could be the right lifestyle change for you.

Want to become a fitness expert? Check out our programs for fitness professionals

 

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Alex Hoffmann

Dr. Alex Hoffmann is the President of the College of Exercise Science. He earned a doctorate in Sports Management from the United States Sports Academy, a master's degree in kinesiology from California State University, Fullerton, and a bachelor's degree in exercise science from Central College. Prior to his career in academia, Dr. Hoffmann worked as Master Fitness Trainer course instructor for the United States Army, and as a strength and conditioning coach, personal trainer, and nutritionist.

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