Skip to main content
take the reality check diet analysis take the reality check diet analysis

Weight Loss

From the effects of the hormone cortisol to the role of genetics in weight loss, this category is packed with everything that you need to know about losing weight the healthy way.

The Beginner’s Guide to Intermittent Fasting

Fasting diets have become highly popularized, but what exactly is intermittent fasting? Find out the facts in this intermittent fasting 101 guide!

The Beginner’s Guide to Intermittent Fasting

Fasting diets have become highly popularized in the health world. However, types of 

intermittent fasting (IF) are not exactly diets, but rather eating patterns that include periods of fasts and feasts.

Nonetheless, becoming a follower of the eating pattern has shown to bare numerous health benefits. The benefits of intermittent fasting include significant weight loss and improvements in cholesterol and blood sugar levels.

With all the various types of intermittent fasting, how is one to choose? Learn how fasting works and which might fit best with personal lifestyles and schedules.

Intermittent Fasting 101

Intermittent fasting is not exactly a diet, but rather an eating pattern. Instead of focusing on not exactly what to eat, IF places emphasis on when to eat.

Fasting and feasting with intent means consuming calories during a specific window of the day. The remainder of the day is essentially devoid of food, or the "fasting" portion.

The most basic form of fasting is a pattern the majority already does. Fasting between the last meal of the day (generally dinner) and breakfast the next morning (hence "break" the "fast"). More extensively in the health world, fasting periods tend to go for longer bouts of time.

Types of Intermittent Fasting

There are seven common types of intermittent fasting, including the following:

1. The 12-Hour Fast: Fast for 12 hours, feast for the remaining 12
2. The 5:2 Plan or Fast Diet: Fast for two days, feast during the other five days of the week
3. Alternate-Day Fasting: Fast every other day, feast the days in between
4. 16:8 or Leangains: Fast for 16 hours of the day, feast the remaining 8-hour window
5. Eat Stop Eat: Fast for 24 hours once or twice per week
6. The Warrior Diet: Fast for about 20 hours each day and feast for the remaining four
7. Spontaneous Meal Skipping: Skip meals spontaneously and randomly

1. The 12-Hour Fast

Followers simply fast for half the day and feast for the other 12-hour remainder. The hours are flexible, too. One can eat from 8:00 a.m. to 8:00 p.m., 11:00 a.m. to 11:00 p.m., etc.

Also considering one sleeps seven to nine of those 12 hours, this form is relatively simple to follow. Ultimately, the 12-Hour Fast is recommended to be a good start for intermittent fasting newbies.

2. The 5:2 Plan or Fast Diet

Also known as The Fast Diet, the 5:2 method of intermittent fasting was popularized by Michael Mosley. This form involves restricting calorie intake to 25 percent of needs two days a week and eating normally the rest.

Put simply and as the name suggests, five days of the week are normal eating days. The other two restricts calories to 500 to 600 per day. Most people split the two fasting days apart (i.e. Monday and Wednesday, Tuesday and Thursday, etc.) to soften hunger pangs from a two-day fast.

3. Alternate-Day Fasting

Also known as Up Day/Down Day, alternate-day fasting (ADF) suggests fasting every other day. On the feasting days, one can eat whatever is desired.

A bounty of evidence showing ADF is a powerful weight loss method, including reducing body fat and inflammation in the body. Furthermore, ADF has shown to be effective at preserving muscle mass compared to daily calorie restriction.

Followers might also modify this form of IF plan, which includes consuming 500 calories on fasting days. This is considered much more sustainable than doing full fasts on fasting days whilst indicating to be still effective.

4. Leangains or 16:8

Touted as the "birthplace of intermittent fasting," Leangains was founded as Martin Berkhan. Martin is also known as "the Khan, godfather or high priest of intermittent fasting."

Leangains encourages one to eat all daily calories in an 8-hour window and fast the other 16 hours of the day. It is "specifically tailored to fitness and strength training and for those wanting to get as lean and strong as possible. In comparison to other intermittent fasting based diets much more emphasis is put on proper pre- and post-workout nutrition."

The rest of the diet's recommendations are orthodox gym advice. This includes eating higher protein food and eating more calories on training days and fewer calories on off days.

5. Eat Stop Eat

Eat Stop Eat encourages one to use it as a "LONG-TERM strategy to get lean quickly." It is designed so one can fast for 24 hours once or twice weekly while never going a day without eating.

For instance, if finishing dinner on Wednesday at 7:00 p.m., the next meal would be 7:00 p.m. on Thursday. One could also eat breakfast then fast until the next, or lunch-to-lunch, etc. Despite the eating schedule, the end result proves to be the same.

Some fasts allow some solid foods during fasts, including produce and a low amount of lean proteins. But water, coffee, and other non-caloric beverages are only allowed with Eat Stop Eat.

6. The Warrior Diet

Founded by Ori Hofmekler, the Warrior Diet might not be for beginners. The warriors fast for about 20 hours every day and eat one large meal at night. However, fasting allows small amounts of whole vegetables, fruits, and protein sources.

The Warrior Diet is based similarly to the tenants of the Paleo diet. It encourages one to stick to whole foods such as meats, poultry, fish, vegetables and whole grains.

7. Spontaneous Meal Skipping

This type of fasting is not exactly structured, but a loose eating pattern one does not have to strictly follow. What’s more, there are still expected benefits its followers can reap.

In spontaneous meal skipping, simply omit meals from sporadically. Such random fasts may include perhaps not feeling hungry or are too busy.

This form of fasting also reinforces the importance of listening to hunger and satiety cues. It lowers the risk of temptation when it comes to food as well.

Intermittent Fasting Benefits

From weight loss to heart health, there is a bounty of research exploring the benefits of intermittent fasting.

Weight & Fat Loss

The hope to lose fat and weight is one of the biggest motivators for following any eating plan or schedule. Even though weight loss is achieved with a calorie deficit, intermittent fasting does not promote calorie restriction.

However, a reduction in calories can run parallel with such a short eating window. Existing research also suggests intermittent fasts plus energy restriction is best for weight loss.

Weight and fat loss may likewise be the result of stabilizing hunger hormones.

Hunger Hormone Stability

Ghrelin and leptin are two hormones that help to control appetite and food intake. Ghrelin stimulates hunger while leptin helps to induce satiety.

If they become uncontrolled, leptin reduces and ghrelin increases, ultimately growing the risk of excessive food intake. The claim is that intermittent fasting stabilizes these hormones, in turn, managing hunger and weight.

A link between insulin and hunger also exists. Insulin is a fundamental hormone required to use glucose as energy. It assists in glucose entry into the cells following carbohydrate intake.

Insulin resistance can heighten hunger and cravings, especially to foods rich in carbohydrates and sugar. Being resistant to insulin likewise makes it difficult to lose weight and easier to gain it.

Intermittent fasting, however, shows to improve insulin sensitivity. This can help control hunger and make weight loss more manageable and effortless. Being more sensitive to insulin lowers the risk of diabetes, too.

Intermittent Fasting & Muscle Gain

Intermittent fasting is vastly explored for weight loss, which is essentially opposing for gaining muscle. This is because a caloric surplus is needed to gain muscle. 

That being said, a large component of gaining muscle is diet. Muscle tissues also grow in the presence of resistance training, in which they undergo damage and stress. Following a workout, the muscles need adequate rest and fuel to regenerate and grow.

Research is limited regarding the effects of intermittent fasting on muscle gain. However, a study published in the Journal of Translational Medicine researched modified IF during resistance training in healthy resistance-trained males. The IF group consumed 100 percent of energy needs in an 8-hour period, in which they fasted the remaining 16 hours. The other group consumed meals and matched calories throughout 12 hours.

Paired with resistance training, intermittent fasting resulted in decreased fat mass, while maintaining muscle mass and strength. It is also important to mention the athletes still maintained energy intake and scheduled workouts.

Ultimately, those wanting to gain muscle can benefit from an IF eating pattern if ensuring appropriate nutrient needs.

Decreased Risk of Heart Disease

Heart disease is often a risk in those considered overweight and obese. With weight loss occurring in some intermittent fasters, a decrease in heart disease sounds convincing.

There is some research indicating intermittent fasting lowers triglycerides more than regular diet. Additional research shows fasting may reduce total cholesterol, LDL, triglycerides and increase HDL levels. Improving these biomarkers can lower the risk of heart disease.

However, some research has indicated better heart health and lower "bad" cholesterol levels in those who fast. Conversely, one research study conducted on mice found the muscles of the heart thickened over six months of intermittent fasting.

Research published in the Journal of the American Society of Hypertension suggests IF may improve blood pressure variances. More specifically, intermittent fasting decreased BP values in terms of office and ambulatory blood pressure monitoring (ABPM) measurements.

Other Explored Benefits of Intermittent Fasting

Research related to intermittent fasting is ongoing and various. Other explored benefits may relate to:

• Cancer: The UCSF suggests fasting in combination with a plant-based diet may be beneficial for general cancer prevention.

• Neurodegenerative disorders: Intermittent fasting may be useful for successful brain aging and protect against Alzheimer's and Parkinson's diseases.

• Longevity: Some of the most profound research of IF is its potential to add on precious years of life. "Intermittent fasting may be the center of increasing lifespan," reports the Harvard Gazette.

Downfalls & Side Effects of Intermittent Fasting

The benefits of intermittent fasting are none-the-less compelling. Besides, there is research that supports such intriguing claims.

However, whereas most IF methods are considered to be safe, consult with a clinician before starting any diet or eating regimen. This is to ease any side effects and risks of IF, including fatigue, dizziness, shakiness, and brain fog.

Intermittent fasting may not be suitable for the following populations and those with specific health conditions such as:

• Women who are trying to conceive, pregnant, or breastfeeding
• Children and adolescents
• People with a history of or current eating disorder
• Those managing diabetes and low blood sugars
• People considered to be underweight

Prospective followers should likewise consider the potential downfalls of intermittent fasting. For instance, devoting time to not eating can be a social stressor with work dinners and family holidays. Exercising while in the fasted state can lead to plummeted energy, too.

It is likewise important to note consuming a copious amount of calories is not recommended. Overeating will likely lead to weight gain and deter such benefits. A healthy lifestyle incorporates regular exercise, adequate sleep, and stress management.

Ultimately, implementing eating patterns and strategies should work best for personal lifestyles. And like any sort of diet or eating pattern, their success relies on if they can be sustained long-term. 

How to Intermittent Fast

Interested to see what all the hype is about? If intrigued and ready to start fasting, here are some tips to ease to start an intermittent fasting journey:

1. Consult with a Doctor

Especially if managing any medical condition or taking medication, consult with a clinician before starting intermittent fasting or any new diet. 

Meeting with a Registered Dietitian can also help identify personal goals and create a sustainable plan to meet them.

2. Address Worries and Questions

"What if I get hungry?" and "Can I exercise in a fasted state?" Address these "what ifs" and questions personally and with a healthcare professional. 

Doing so helps clear any confusion and smooth the process of following an intermittent fasting eating pattern.

3. Start Slow & Ease Into the Plan

"Easy does it" is the name of the game when it comes to intermittent fasting. For instance, rather than jumping in quickly and fasting for a 24-hour stretch, start the process slow. 

This may include gradually skipping breakfast, snacks, etc. Fast for longer bouts as the fasting periods become more comfortable.

4. Be Patient with the Process

Especially in the beginning, it is important to not judge the effects in the first day two. This is due to an increased likelihood of experiencing brain fog and low energy. 

At least give the chosen fasting protocol a three-weeks shot chance before throwing in the towel. The longer this sort of lifestyle is practiced, the easier and more regimented it will become.

5. Use Time as an Advantage

Rather than fixating on hunger between fasts and feasts, make the most out of time by staying busy. 

Also, be sure to sleep the recommended seven to nine hours on a nightly basis. Not only is this imperative for overall health, but it can help carve out more of the allotted fasted time.

6. Keep Hydrated

Drink plenty of water, as keeping hydrated helps make the fasting periods easier to get through. Black coffee, tea, and other sugar-free drinks are viable options to sip on.

7. Focus on Quality Foods

While intermittent fasting does not necessarily harp on the foods to consume, nutrient-dense foods should be the focus.

Nourishing the body with whole grains, fruits and veggies, lean proteins, and healthy fats supports weight loss and overall health.

8. Experiment with Various Strategies

Diets and eating patterns are not one-size-fits-all. And what works for one person, may not work for the next. 

So experiment and try different strategies that work best for personal goals, needs, and schedules.


Eat Stop Eat.
The 5-2 Diet Book.

Sydney Lappe's Photo
Written By Sydney Lappe, MS, RDN. Published on August 07, 2018. Updated on June 09, 2020.


Follow @bistroMD

Theme picker

as seen on...
Dr Phil
Lifetime Network
The Biggest Loser
The Doctors