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Intermittent Fasting 101

What is intermittent fasting? Have you heard about intermittent fasting but not sure if it is right for you?

What is autophagy? (Fasting is a way to trigger autophagy).

What can you eat during intermittent fasting?

Does coffee break a fast?

We will explain intermittent fasting, what to eat, what breaks a fast and under which conditions intermittent fasting may be beneficial.

Read on to find out!

This information is for educational purposes only. As with any medical advice, always check with your doctor or healthcare professional for personal and age-appropriate recommendations.

Intermittent Fasting 101

Intermittent fasting involves an eating pattern that rotates between eating and fasting. You follow a set schedule of eating only consuming food during certain hours of the day. 

Calories are not tracked however; it is recommended to eat whole nutritious foods.

There are several types of fasting.

Time Restricted Eating

This is when an overnight fast occurs with an extended period (intermittent fasting). Basically, you are allowed to eat in a short time window.

Alternate Day Fasting or Fasting Intervals

Fasting on one day and eating on the next day.  The fasting day typically is either consuming only water and electrolytes or limiting calories to 600 per day.

Modified Alternate Day Fasting

Also called the 5:2 diet where a person eats normally for 5 days then, restricts calories by 20-30% or to about 600 calories per day for a couple days. 

Fasting Mimicking Diet

This is a diet that is followed for 5 days per month and consists of following a very low calorie, low carbohydrate diet for this period (1).

What is Autophagy?

Autophagy is the process of removing waste products, improving cellular health, and overall health in the body (2). Think of autophagy as cleaning out the trash in the body, detoxing your body, and cleaning out damaged cells.

The regulation of autophagy is controlled by mTor (mechanistic target of rapamycin) (3). Often called the master growth regulator, mTor promotes cell survival and plays a role in the aging process.

Autophagy occurs in both intermittent fasting and calorie restriction (4). Other ways to promote autophagy include a ketogenic diet and exercise (5, 6, 7).

Autophagy Feeding Timeline

How long does it take for autophagy to occur? One study showed the autophagy genes were activated after an eating window of 8am to 2pm which may increase autophagy and have anti-aging effects (8).  

Limiting the eating window may promote autophagy and anti-aging effects.

Types of Intermittent Fasting 101 Programs (Time Restricted Eating)


A 16 hour fast with an 8 hour eating window. Eating usually begins at 12 noon until 8pm when the fast starts. Some may start eating at 10am and start fasting at 6pm to allow an earlier eating window.

An earlier eating windows may increase health benefits (for example, 10am-6pm vs 12 noon-8pm).


A 14 hour fast with a 10 hour eating window. Eating can begin around 10 am and fasting starts around 8pm.


A 12 hour fasting window and 12 hour eating window typically an 8 am to 8 pm eating window.


Migrating Motor Complex and Fasting

The migrating motor complex (MMC) is the cleaning wave of the gut that occurs during fasting (9). The MMC is activated when fasting and when you allow a few hours of fasting between meals. This allows undigested materials to be pushed through the digestive tract. 

Therefore, spacing out meals during the feeding window may further activate the MMC.

What are the Benefits of Intermittent Fasting?

Fasting may be show benefits with (10,11):

  • Improved cognitive function and BDNF
  • Improved insulin sensitivity
  • Cardiovascular health including blood pressure and lipids 
  • Reduced inflammation
  • Cellular repair
  • Cancer prevention
  • Reduced seizures
  • Weight loss

What Can I Eat with Intermittent Fasting?

During intermittent fasting, there is increased focus on the time of eating; however, it is important to eat a whole food, plant rich diet.

Choose healthy foods such as lean meats and fish, vegetables, nuts, seeds, whole grains, and fermented foods (12).

Can You Drink Water While Intermittent Fasting?

Water is so important while fasting! During a fast, you are limiting foods which may contain water (think about fruits and vegetables that contain water) so we must hydrate well.

Make sure to drink healthy fluids throughout the day and water during fasting periods to stay hydrated.

A good way to check your hydration status is to monitor the color of your urine (be careful right after vitamin intake as that can influence the color). Your urine should be light yellow.

Does Coffee Break a Fast?

Black coffee, tea, and water do not have any calories so are unlikely to break a fast. In fact, moderate coffee consumption may boost the benefits of intermittent fasting. 

Consuming calories is what breaks a fast so, food or drinks with calories would be restricted during the fasting period.

Make sure not to put anything in the coffee, tea, or water.

Guidelines for Healthy Intermittent Fasting

Intermittent fasting has health benefits for many people however, fasting may put some individuals at risk.

Conditions that may benefit from intermittent fasting include (13,14):

  • Autoimmune conditions 
  • Cancer
  • Cardiovascular disease
  • Neurological and cognitive disorders (ADHD, Alzheimer’s, anxiety, autism)
  • Prediabetes and diabetes
  • Weight control

People who should not do intermittent fasting include:

  • Children
  • Pregnant or lactating women
  • Individuals with disordered eating
  • Type 1 diabetics
  • Individuals with chronic kidney disease

Always check with your healthcare professional about your individual health condition.

Final Thoughts

Intermittent fasting involves an eating pattern that rotates between eating and fasting. 

Autophagy is the process of removing waste products, improving cellular health, and overall health in the body. 

The migrating motor complex (MMC) is the cleaning wave of the gut that occurs during fasting.

Intermittent fasting may be beneficial for insulin resistance, blood glucose, blood pressure, inflammation, weight loss, and brain health.

It is important to stay hydrated during fasting and black coffee, tea, and water do not contain calories so do not break a fast!

Children, pregnant and lactating women, individuals with disordered eating, type 1 diabetics, and kidney disease should not practice intermittent fasting.

Always check with your health professional about your individual recommendations.

Remember, what you eat is important for health and disease prevention. 

What you absorb (breaking down the food) and assimilate (gets into the cells) is critical. 

Test don’t guess.

Contact me to schedule an appointment to review your personalized nutritional health.

© Amy Archer RDN, CLT, CHWC

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