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Intermittent Fasting: Benefits and Comprehensive Guide

author avatar Dr. Eric Berg 06/17/2024

Intermittent fasting is a mealtime pattern of time-restricted eating and fasting periods widely used for metabolic health benefits.

In addition to promoting weight management and balanced blood sugar control, intermittent fasting may also help reduce inflammation and protect against chronic diseases such as diabetes.

Discover the beneficial health effects of intermittent fasting and learn how to transition into time-restricted eating successfully. 


Intermittent fasting plate

What is intermittent fasting?

Different fasting routines have been practiced worldwide for millennia and are often observed at certain times of the year, such as during Ramadan or Lent.

Traditional fasting, also known as periodic fasting, involves not eating for an extended period of time, typically a few days. 

In contrast, intermittent fasting involves consistently alternating between periods of fasting and designated eating windows. 

This method of time-restricted feeding is often used for weight loss, lowering blood pressure, managing blood sugar balance, and reducing the risk of various health conditions.

Watch the video below to learn more about the basics of intermittent fasting.

How to Do Intermittent Fasting Intermittent Fasting Basics for Beginners

5 benefits of intermittent fasting

Intermittent fasting has been widely studied for its beneficial effects on weight and disease management, including conditions of the brain, heart, and gastrointestinal tract. 

Here are five incredible health benefits of intermittent fasting. 

1. Boosts weight loss

Constant grazing and snacking lead to the continuous release of insulin, a metabolic hormone that helps regulate blood sugar levels. However, insulin also stimulates fat storage, which explains why snacking is a primary contributor to weight gain.

During periods of fasting, blood sugar levels remain stable, reducing insulin release linked to better weight control.

In addition, fasting puts the body in ketosis, the metabolic state of fat-burning. During ketosis, the body switches from using sugar as the primary fuel source to burning fat. This can promote significant weight loss without the need for calorie restriction. 

A study published in the Journal of Translational Medicine found that intermittent energy restriction due to fasting was as effective as continuous energy restriction at promoting weight loss and improving metabolic health.

2. Enhances insulin sensitivity 

A diet high in carbohydrates, processed foods, and sugar can lead to insulin resistance. 

This metabolic disorder is characterized by the body’s inability to respond to insulin’s attempts to lower blood sugar. This prompts the pancreas to produce more insulin, further contributing to insulin resistance and worsening blood sugar control. 

Insulin resistance, which is also known as metabolic syndrome, can lead to various health issues, including type 2 diabetes, polycystic ovarian syndrome (PCOS), and cardiovascular disease.

Data from a large systematic review and meta-analysis published in the International Journal of Endocrinology found that intermittent fasting significantly improved blood glucose and fasting insulin levels in people with metabolic syndrome.


Man checking blood sugar

3. Cellular repair

Intermittent fasting can trigger autophagy, a biological process in which the body recycles damaged cell parts to generate energy and enable cellular repair. 

Autophagy helps destroy malfunctioning cells and supports healthy inflammatory responses associated with a lower risk of cancer and autoimmune conditions. 

Autophagy pathways activate when blood sugar and glycogen stores are depleted, which may be achieved by fasting for 16 to 18 hours. 

However, combining intermittent fasting with a low-carb ketogenic diet helps keep blood sugar and glycogen reserves low, which can help achieve autophagy more quickly. 

4. Lowers the risk of chronic diseases

Fasting has been found to lower inflammation throughout the body, including in the brain and gastrointestinal tract.

Chronic inflammation is a known risk factor for many serious health conditions, including heart disease, diabetes, cancer, and neurodegenerative disorders. 

A study published in Medicina investigated the effects of fasting in the management of ulcerative colitis. The authors concluded, Inflammation markers, such as CRP and calprotectin, were significantly reduced after eight weeks of intermittent fasting.” 

5. Promotes brain health 

Intermittent fasting is associated with a reduced risk of Alzheimer’s and Parkinson's disease

Fasting helps prevent plaque formation in the brain and supplies the central nervous system with ketones. These organic acids are a by-product of fat metabolism and are a preferred fuel source for brain cells that support optimal cognitive function and memory.

Research published in Nutrition Reviews found that prolonged periods of caloric restriction in animals reduced protein tangles in brain tissue associated with Alzheimer's disease. The study also found that fasting enhanced neuronal health and cognitive function.  


Water fasting concept

Types of intermittent fasting

There are many forms of intermittent fasting, all of which have profound health benefits, including fat loss, improved heart health, and balanced insulin levels. 

  

Here are five common types of intermittent fasting patterns.

1. 16:8 method

The 16:8 fasting method involves 16 hours of fasting followed by an eight-hour eating window. For example, one could eat lunch at noon and dinner around seven o’clock, then fast until noon the following day.

Other variations of the 16:8 fasting pattern include the 18:6 and 20:4 methods in which you fast for 18 or 20 hours and have a six- or four-hour eating window. 

These patterns achieve a prolonged fasting period that helps extend autophagy while maximizing weight loss benefits and cognitive improvements. 

2. Alternate-day fasting

Alternate-day fasting is a form of intermittent fasting characterized by fasting every other day. 

The alternate-day fasting plan has two versions. The most common variation is zero-calorie fasting on fasting days. However, some dieters reduce their caloric intake to between 500 and 600.


OMAD diet concept

3. One Meal A Day

One Meal A Day (OMAD) is a popular intermittent fasting pattern in which dieters eat only one meal daily. 

OMAD, also known as the 23:1 fasting method, consists of fasting for 23 hours, followed by a one-hour eating window.

OMAD every other day is a more restrictive version of OMAD that combines 23:1 fasting with alternate-day fasting. OMAD every other day involves eating one meal every two days to boost weight loss.

Abstaining from eating a few days a week may be especially beneficial for those with excessive body weight or a slow metabolism.

4. Dry fasting

Dry fasting is characterized by abstaining from food and liquids for a short time, typically no longer than one day. Dry fasts are categorized into two groups: soft dry and hard dry.

Soft dry fasts allow water to be used for showering, brushing your teeth, washing your hands, or other hygiene or cleaning tasks. 

Contrarily, hard dry fasts prohibit any contact with water. Dry fasts can quickly become dangerous, as the body can’t survive without water for extended periods. 

However, intermittent dry fasting from dawn to sundown is common during Ramadan, and a study published in the Journal of Human Nutrition and Dietetics found that dry fasting helps reduce body mass index (BMI) in healthy adults.

5. Prolonged fasts

Prolonged fasts involve fasting for 24 hours to several days at a time, typically once a week or month. 

These fasts are meant to increase autophagy, which peaks around 48 hours of fasting, according to an animal study published in Cells.

However, this fasting method is the most extreme and isn’t ideal for beginners. 

Refeeding after a prolonged fast must be carefully planned to avoid refeeding syndrome. This potentially serious condition can cause heart palpitations, bloating, mood swings, and confusion.

It’s vital to consult a healthcare professional before practicing prolonged fasting to avoid adverse health effects. This is especially important for individuals with preexisting health conditions and those taking prescription medications. 


Hungry woman waiting to eat

Is intermittent fasting safe?

When paired with a balanced diet, an intermittent fasting plan is safe for most people and has been shown to support healthy metabolic function and reduce disease risk.  

However, a strict intermittent fasting diet can become hazardous without optimal nutrition or calorie intake. 

Consuming inadequate amounts of calories and nutrients can lead to unhealthy weight loss and nutritional deficiencies associated with mood disorders, dizziness, fatigue, and other adverse health effects.

Here are some considerations to ensure intermittent fasting is right for you.

Who should be careful or avoid it?

Though fasting is generally considered safe, breastfeeding or pregnant mothers should avoid intermittent fasting. 

Expectant mothers require additional nutrients and calories to support fetal development. Fasting may increase the risk of deficiencies linked to premature delivery, lowered IQ, and congenital disabilities. 

Those with histories of eating disorders should also avoid intermittent fasting to avoid a potential relapse into unhealthy eating habits.

Additionally, individuals taking antidiabetic drugs or insulin are at risk of dangerously low blood glucose when fasting. This could lead to poor cognition, slurred speech, fatigue, and seizures in severe cases. 


Keto diet foods

What to eat when you’re not fasting

Because intermittent fasting can contribute to nutritional deficiencies, it’s best practiced alongside a balanced diet rich in whole food. 

Healthy Keto®  is a low-carb, high-fat diet focusing on nutrient-dense, quality foods like wild-caught fish, healthy fats, grass-fed beef, pasture-raised eggs, and organic produce.

Combining Healthy Keto with intermittent fasting maximizes the metabolic and cognitive benefits of periodic calorie restriction. 


“If you’re doing intermittent fasting without keto, you may prevent some of the beneficial effects of fasting due to high intake of carbohydrates and sugars,” explains Dr. Berg. 

A Healthy Keto diet avoids sugar and carbohydrates such as fruit, starches, rice, wheat, and corn. These foods spike insulin and lead to blood sugar fluctuations, which directly counteract the benefits of fasting.


Woman eating a scheduled meal

How to get started with intermittent fasting

The goal of following an intermittent fasting eating pattern is to abstain from consuming any food and calorie-dense beverages during fasting periods. 

If you are new to intermittent fasting, it’s recommended that you start slowly. This will allow your metabolism to adapt to the change in eating frequency. 

Three meals a day without snacking is an achievable first step for most dieters.

As you become more comfortable with fasting and no longer experience cravings or hunger, you can skip breakfast and eat only two meals per day following the 16:8 fasting method.

Those with a significant amount of weight to lose may benefit from shortening their eating windows to a 20:4 schedule or extending their fasting to OMAD or OMAD every other day.


Woman craving sweets

Intermittent fasting tips and troubleshooting 

Many people new to intermittent fasting start too quickly, which can lead to impulsive behaviors such as snacking or reverting to unhealthy eating habits.

Here are four intermittent fasting tips to help you stay on track.

1. Avoid snacking

One of the most common mistakes dieters make when intermittent fasting is snacking during the eating window. 

Consuming even low-calorie foods or snacks labeled as healthy can trigger insulin release, which stops fat-burning and reduces the beneficial effects of calorie restriction.

Once the body adapts to the profound effects of intermittent fasting, you won’t feel hungry or need to snack between meals. 

2. Limit carbohydrates and increase healthy fats 

Regularly consuming carbs like sugar, bread, pasta, soda, or wine will make it more difficult to fast. 

Carbohydrates can cause significant insulin spikes and blood sugar fluctuations, which can lead to cravings and hunger sensations. 

In contrast, healthy fats found in olives, avocados, oily fish, and nuts are satiating and help you fast for longer. 

Bulletproof coffee is an excellent way to curb hunger and support energy levels without breaking your fast. 

Also known as keto coffee, bulletproof coffee contains black coffee, butter, and medium-chain triglycerides (MCT) oil. These pure fats won’t trigger insulin release and promote satiety without interfering with fat-burning or autophagy. 

However, it’s essential to avoid calorie-containing beverages during fasting, such as soft drinks, juices, milk, or coconut water.


Dietary supplements

3. Support nutrient levels 

Without optimal nutrition, fasting can lead to nutrient deficiencies and electrolyte imbalances, which can cause feelings of weakness, fatigue, and irritability. 

Supplementing while fasting is vital to reduce the risk of depleting essential nutrients, especially when practicing OMAD or water fasts.

Some of the best intermittent fasting supplements include B vitamins, a trace mineral complex, and a sugar-free and potassium-rich electrolyte powder.  

4. Stay hydrated

Working out while fasting can enhance weight loss, increase growth hormone levels, and boost autophagy. 

Despite its benefits, fasting while exercising can lead to dizziness, lightheadedness, and other side effects when electrolyte levels are depleted. 

To replenish lost electrolytes and promote energy production, it’s vital to stay hydrated using an electrolyte powder before, during, and after your workout. 

However, avoid pre-workout powders containing branched-chain amino acids (BCAA) while fasting. BCAAs are proteins that can trigger insulin release and may break your fast. 


Fasting woman checking watch

How long does it take to see results?

Intermittent fasting can produce visible results for weight loss in a few weeks. Dieters who stick to regimented fasting and eating periods can lose up to three pounds weekly. 

A systematic review of studies published in the Canadian Family Physician found that intermittent fasting was as effective as calorie restriction for weight loss. 

The authors also found that intermittent fasting can help obese individuals with type 2 diabetes improve glycemic control.

Those who have a significant amount of weight to lose may burn six pounds per week. However, how much weight you can lose when fasting depends on caloric intake and the fasting method used. 

OMAD and OMAD every other day are popular for rapid weight loss and help dieters tap into fat stores more efficiently. 


Plate with letters spelling fast

Key takeaways

Intermittent fasting is an eating pattern that restricts food consumption to a specific time frame. 

It’s commonly used to lose weight but has also been linked to various health benefits, such as reduced disease risk and improved cognitive function. 

There are many types of fasting methods, such as the 16:8 method, alternate-day fasting, and OMAD. Regardless of which fasting regime you plan to start, it’s recommended to start slowly, avoid snacking, and combine intermittent fasting with Healthy Keto.


FAQ

1. What are the basic rules of intermittent fasting?

The first rule of intermittent fasting is to avoid snacking between meals, as eating will spike insulin and break a fast. Water, tea, and coffee with butter are acceptable while fasting as long as these beverages contain no sugar or carbs. 

Taking B vitamins, trace minerals, and electrolytes can boost energy and reduce the risk of deficiencies. In addition, fasting in combination with a nutritious high-fat diet such as Healthy Keto® ensures optimal nutrition and promotes satiety, which helps achieve prolonged fasting periods.  

2. Can I drink liquids while fasting?

Yes. Water is the best liquid to drink while fasting. However, beverages that don’t raise blood sugar levels, such as lemon water, coffee, stevia-sweetened electrolyte drinks, and tea, can also be consumed during a fast. 

Avoid soft drinks, milk, bone broth, or other liquids with carbohydrates, sugars, or protein, as these can trigger insulin release and break a fast.

3. Can I take supplements while fasting?

Yes, you can take supplements while fasting. Supplements such as B vitamins, vitamin D, cod liver oil, electrolyte powders with potassium, trace minerals, and wheat grass juice powder can support energy production during fasting while reducing the risk of nutrient deficiencies. 

However, check the ingredient list of supplements and avoid those that contain sugars, maltodextrin, and other fillers that can raise blood sugar levels and break a fast.

4. Can I work out while fasting?

Working out while fasting is safe and may enhance weight loss and performance. Both intermittent fasting and exercise stimulate growth hormone production, which helps build muscle, speed up recovery, and boost fat-burning up to 30 percent. 

5. Will fasting cause muscle loss?

No, intermittent fasting won’t cause muscle loss if combined with a nutritious diet such as Healthy Keto and regular resistance training. 

6. Can I do intermittent fasting while pregnant?

No, it’s not recommended to practice intermittent fasting while pregnant. Intermittent fasting while pregnant may lead to inadequate intake of calories and nutrients, which can hinder fetal development and increase the risk of congenital disabilities. 

7. Can children do intermittent fasting?

No, children shouldn’t practice intermittent fasting as they’re still growing and developing, which requires a steady supply of nutrients and energy throughout the day. 

Restricting children’s eating windows can lead to nutritional deficiencies and impede healthy growth and development.


Sources

  1. https://pubmed.ncbi.nlm.nih.gov/30583725/ 

  2. https://pubmed.ncbi.nlm.nih.gov/35371260/ 

  3. https://pubmed.ncbi.nlm.nih.gov/37629743/ 

  4. https://pubmed.ncbi.nlm.nih.gov/37043764/

  5. https://onlinelibrary.wiley.com/doi/full/10.1111/jhn.12042 

  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5492018/ 

  7. https://pubmed.ncbi.nlm.nih.gov/32060194/

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