What Is Intermittent Fasting? A Complete Guide To IF

What exactly is Intermittent Fasting?  What are the benefits of fasting? Dive into the basics of intermittent fasting below!

What is Intermittent Fasting?

Intermittent Fasting (IF) is an eating pattern where you cycle between periods of eating and fasting, according to Healthline. 

Humans have actually been fasting for years. “Up until about 12,000 years ago, humans got their food by hunting, gathering or fishing. As foragers, they would fast until they found, caught or killed their food. There was no breakfast upon waking, or leftovers for lunch. They ate opportunistically, according to Inverse.

Also at the time, humans did not consume nearly as much as we do now. When there was no electricity and no refrigerators, humans ate from sun up until sundown. Today, we eat all hours of the day. If it’s dark when we wake up, we can still have access to food. If we want a midnight snack, the refrigerator light is always working.

Do you want to learn more about fasting? Check out our ultimate intermittent fasting guide!

Types of Intermittent Fasting


Fast for 16 hours per day, eat for 8 hours per day. For example, someone utilizing the 16:8 method may use 12 pm-8 pm as their eating window. 


During 2 days of the week eat 500-600 calories. The other 5 days of eating is normal. 

Alternate Day Fasting (ADF)

Every other day choosing to not eat anything from dinner one day until dinner the next day. This is a 24 hour fast that many people do every other day. 


OMAD stands for One Meal A Day. This involves fasting for 23 hours per day and then eating one large meal in a 60-minute window. OMAD has been gaining popularity, with people swearing by it as a weight-loss method as well as a way to tackle chronic disease and other health issues.

There are a few variations of OMAD. Some people fast for 20 hours and eat for 4 hours. Their window then includes a snack, a meal, and sometimes an additional snack or dessert.

Other Variations

There are many other variations than the options listed above! Some other options are 12:12, 20:4, 18:6, etc. You can customize your fast to what works best for you. For more information, check out our guide to the different types of intermittent fasting.

Intermittent Fasting Benefits

There are so many benefits of IF. Here are just a few of the many benefits.

Weight Loss

According to Vox, the body shifts into fat-burning mode when it doesn’t get food for an extended period of time. That’s because the body’s first source of fuel is glycogen, and it only turns to burning body fat once that quickly available energy source is depleted. When you fast for long enough, you drive down stores of glycogen and start burning fat tissue. Additionally, IF generally means you are eating fewer calories as you are not eating for a certain window of time. 

Insulin resistance

According to Dr. Jason Fung, “insulin itself causes insulin resistance. As we (doctors) prescribe insulin to type 2 diabetes, patients don’t get better, they get worse. Their blood glucose is better, but they gain weight and they still develop all the complications – heart disease, stroke, kidney disease, blindness, etc.”

“The correct treatment is to empty out the BODY, not just the blood of the excessive glucose. How? Low carb diet and intermittent fasting. And guess what? That’s EXACTLY what we see clinically. As we (doctors) start fasting type 2 diabetes patients, they lose weight, their medication requirements go down and eventually it reverses.”

Reduced inflammation

There are a number of factors in our day-to-day lives that can trigger inflammation throughout the body. High-stress levels, exposure to cigarette smoke, pollution, and poor sleep patterns can all result in inflammation, according to dietician Chole McLeod.

Fasting may assist in managing inflammation by:

  • Changing how compounds and proteins interact with each other, inhibiting inflammatory pathways.
  • Reducing inflammatory biomarkers, such as CRP, homocysteine and cholesterol ratios.

Heart health

According to Mayo Clinic, regular fasting can decrease your low-density lipoprotein, or “bad,” cholesterol. It’s also thought that fasting may improve the way your body metabolizes sugar. This can reduce your risk of gaining weight and developing diabetes, which are both risk factors for heart health and heart disease.

Brain health

Intermittent fasting may have important benefits for brain health. It may increase the growth of new neurons and protect the brain from damage.


When you fast, your cells are given time to detox and recycle, so your body can slow down the aging process and help prevent age-related diseases. (Physical IQ)

Cellular repair

“Cycles of fasting can reset and rejuvenate the human body,” said Valter Longo, director of the Longevity Institute at the University of Southern California. “Periods with no food help the body eliminate and replace damaged cells with new ones through a process called autophagy.”

Increased Human Growth Hormone (HGH)

HGH is a hormone made by the pituitary gland (the master gland), which plays a huge role in the normal development of children and adolescents as the name implies. However, it also plays a role in adults. HGH deficiency in adults leads to higher levels of body fat, lower lean body mass and decreased bone mass. (Diet Doctor)

Fasting is a great stimulus to HGH secretion. Fasting has the potential to unleash the anti-aging properties of HGH without any of the problems of excessive HGH (prostate cancer, increased blood sugar, increased blood pressure). For those interested in athletic performance, the benefits are even greater. -Dr Jason Fung 

While there are many benefits of fasting, “IF is another tool in our nutrition toolbox. It is not a diet and is not a quick fix. It can be a powerful eating approach for fat loss and a variety of other benefits.” -Lauren Gleisberg 

Intermittent Fasting Resources

There are so many great resources to help you be successful on your IF journey.


Intermittent fasting apps can be really handy to track your fasted hours.

Zero app

The Zero app helps you to keep track of your fasting window and eating window. You can also sync this app with your Health app to keep track of your weight, trends, fasting history, and more! 

LIFE app

The LIFE app is another app that is helpful for tracking your fasts. LIFE has circles that allow you to interact and share your fasts and fasting journey with others. You can also read informational articles and chat with fasting experts if you need any help.

For more information, you can read about our full guide to the best intermittent fasting guides.


For more information, you can read our guide to the best intermittent fasting books.

Bottom Line

Intermittent fasting is a pattern of eating that can benefit your body and health in many different ways. If you have additional questions regarding intermittent fasting, I have answered the most common IF questions to help you out.