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Intermittent Fasting 2023 Guide: IF Diet Plan Types and Weight Loss Benefits

Intermittent Fasting is one of the biggest 2023 health trends. Here's a research guide on the weight loss benefits, scientific medical studies and top IF diet plans to review.


Intermittent Fasting in 2023: Beginner’s Guide to IF Diet Plans and Health Benefits

Intermittent fasting is one of the hottest diet plans in 2023 and was the most searched diet program in 2019 according to Google Trends search data. In a nutshell, intermittent fasting is advanced living. It is a health hack the world is waking up to in the new 2023 decade and will continue to become an in-demand topic of interest as the wellness effects and literature begin to stack up fast.

As more research validates the weight loss benefits of intermittent fasting, it has become even more popular option for those seeking to live a healthy lifestyle. Also known as IF, intermittent fasting is purported to enhance weight loss, boost longevity, and increase your energy, all without the strictness associated with a traditional diet. We have even saw prominent doctors recommend intermittent fasting dieting in 2023 when Dr Oz's System 20 was released where it was based on adhering to the IF practice of eating in cycles and timing meals.

However, many are new to intermittent fasting and the notion of “eating less to live longer so you can eat more”? The good news is you've come to the right place if fasting intermittently seems like a foreign concept as we will do an essential deep-dive of ‘breaking the fast' and review the in-demand daily time-restricted feeding program research. Today, we’re explaining everything you need to know about the ancient intermittent fasting activity; including how fasting works, what foods to eat, the various types of IF diet plan approaches and what science says about intermittent fasting benefits.


What is Intermittent Fasting?

intermittent fasting 2023 guide

Intermittent fasting (IF) is an eating pattern where you cycle back and forth between time periods of fasting and eating on a daily basis. Instead of emphasizing which foods to eat or how much to eat, intermittent fasting focuses more on when to eat those foods, essentially giving you a smaller window of eating hours to allow the body to not digest foods and meals all day long. That’s why many people describe intermittent fasting as an eating pattern instead of a diet where it practices food scarcity to trigger metabolic switching.

Technically, most of us already have some type of intermittent fasting routine. If you have dinner at around 7 pm every night and eat breakfast at 7 am the next morning, then your body is fasting for 12 hours every day. A typical intermittent fasting system, however, involves a longer fast. However, most ‘Westerners' on the ‘standard American diet' consume three square meals a day plus added in snacking time which negates the purported wellness effects of the discipline intermittent fasting dieting schedule.

The most popular IF system involves fasting for 16 hours and feeding for 8 hours. You might have your last meal at 7 pm, for example, and break your fast with a late breakfast at 11 am the next morning. Since most of your fasting is done overnight as you sleep, it’s a reasonable target to aim for.

Some intermittent fasters take things a step further with a 20 hour fast and 4-hour feeding window. Others even drop it down to one meal a day, or an OMAD system, where you fast for 23 hours a day and have one gigantic meal whenever you want. This is the most extreme version of intermittent fasting.

Others do daily fasts, like a 5:2 cycle, where you fast for two days a week. There are also religious fasts – like Ramadan in Islam, where Muslims abstain from food and water from sunrise to sunset for one entire month.

Where Did Intermittent Fasting Come From?

Intermittent fasting has been very trendy in recent years. It’s fair to say that intermittent fasting has exploded in popularity since 2017:

Google search data showing intermittent fasting trends rising in 2023

As you can see, Google Trends shows limited search activity for intermittent fasting until around 2012. There were a few blips of activity between 2012 and 2016, although intermittent fasting didn’t really catch on until 2017, at which point it really started to take off.

Could 2023 be the year intermittent fasting really takes off? Google certainly seems to think so. Based on search activity at the end of 2019 and the start of 2023, Google believes 2023 will be the year more people search for intermittent fasting than any other year (the dotted line).

Intermittent fasting, however, is not new. In fact, IF traces its roots back thousands of years all the way to hunter-gatherer times. In ancient times, humans had to survive in an era without supermarkets, refrigerators, and 24/7 fast-food restaurants.

Sometimes, humans had to go days without food. During hard winters, humans might have had to spend months on meager rations. As a result, humans have evolved to be able to function without food for extended periods of time. Some intermittent fasting advocates even argue that fasting is more natural than eating 3 meals per day!

Fasting is also performed for religious reasons. Fasting plays an important role in Islam, Christianity, Judaism, and Buddhism. During Ramadan, for example, Muslims fast from dawn to dusk for an entire month. In fact, fasting for the month of Ramadan is one of the Five Pillars of Islam, and it’s mentioned in three consecutive verses in the Quran.

In summary, intermittent fasting has been very trendy in recent years, but it traces its roots all the way back to hunter-gatherer times, and some intermittent fasting advocates argue that IF is a more natural way to live than eating three meals per day.

Types of Intermittent Fasting

There are no strict rules governing what is considered intermittent fasting and what is not considered intermittent fasting. If you eat your last meal at 7 pm and have breakfast at 7 am, for example, then you’re intermittently fasting for 12 hours and eating for 12 hours. A 12/12 split isn’t the hardest or strictest version of intermittent fasting, but it’s a good start for those new to IF.

Here are some of the most popular types of intermittent fasting methods available today:


Under a 16/8 split, you fast for 16 hours and eat for 8 hours in each 24 hour period. A popular system would be to have your last meal at 6 pm and break your fast at 10 am. Others have their last meal at 7 pm and break their fast at 11 am.


If you find a 16/8 split too difficult, or if you just want to dip your toes into IF, then a 12/12 split is a good introduction. It teaches you some level of discipline without interfering with your normal eating habits. However, critics will claim the benefits of a 12/12 routine are minimal.


Under an eat-stop-eat IF system, you would fast for 24 hours once or twice a week. You might have dinner one night, for example, and then avoid eating until eating dinner the next night.


Under a 5:2 system, you might eat normally five days a week and then fast, or maintain a limited diet, the other two days.


A One Meal A Day (OMAD) system is the most extreme version of intermittent fasting. Under an OMAD system, you fast for 23 hours and have just one meal in every 24 hour period. Some people enjoy this system because they can just focus on making and eating one good, big meal. Others find this system very difficult to follow.

Ultimately, the 16/8 method is the most popular system for new and advanced intermittent fasters alike. It’s reasonable for most normal people to follow. It appears to offer good weight loss benefits.

How Does Intermittent Fasting Work?

Supporters of intermittent fasting will tell you that IF is linked to several crucial benefits.

As mentioned above, some people believe IF is a more natural way to live: they claim the human body has evolved to fast intermittently.

Further down, we’ll explain what science has to say about intermittent fasting. However, here are some of the purported benefits of intermittent fasting according to supporters:

Weight Loss

The most popular purported benefit of intermittent fasting is that it leads to weight loss. When your body is fasting, it needs to get its energy from somewhere, so it burns stored fat. Meanwhile, during the feeding phase, your body gets energy from the foods you eat, like carbs.

Higher Energy Levels

If you have ever followed a low-calorie diet, you probably felt your physical and mental energy plummet. That’s why many people hate dieting. With intermittent fasting, however, supporters claim you’ll feel increased energy levels compared to other diets.

Healthier than a Calorie-Reduced Diet

Supporters of intermittent fasting diets claim it’s healthier than a starvation diet, low-carb diet, high-fat diet (keto), or other trendy diets. They claim our bodies have evolved to fast, and that fasting is more natural than something like a calorie-reduced diet or high-fat diet.

Easier to Follow

You might have the best diet system in the world, but it’s not going to work for most people if it’s hard to follow. Intermittent fasting is seen as one of the easiest plans to follow. You can eat the same food you normally eat. In fact, you can eat whatever you want. You don’t have to worry about preparing six small meals per day or cleaning things up. At the more extreme end, IF may only require you to prepare one meal a day.

Eat What You Like

Do you like eating steak twice a week? You can do that with intermittent fasting. Do you want to go fully vegan? You can do that with IF too. IF is an eating pattern, not a strict diet system. Eat whatever you want, but just be careful at which times you eat.

Raises Human Growth Hormone (HGH) Levels

Intermittent fasting purportedly increases human growth hormone (HGH) levels. HGH is linked with greater fat loss and muscle gain, among other benefits.

Boosts Insulin Sensitivity

Fasting improves insulin sensitivity. When you fast, insulin levels drop dramatically. When your insulin levels are low, your body makes stored body fat accessible for energy, potentially accelerating weight loss.

Encourages Cellular Repair

Your cells start to repair themselves when your body fasts. When fasting, your cells engage in something called autophagy, where they digest and remove old and dysfunctional proteins that build up in cells. This is a crucial part of the cellular repair process. If you never fast, then your cells may have trouble repairing themselves.

Improves Gene Expression

Fasting appears to change the function of genes, especially genes related to longevity and disease protection.

These benefits all sound good, but does the science actually support them? Find out in the next section.

Benefits of Intermittent Fasting: What Does Science Say?

Are any of these purported benefits real? Or is intermittent fasting just the latest fad diet?

First, let’s talk about weight loss because that’s the benefit most readers care about the most. In fact, according to this study published in the International Journal of Obesity in 2015, weight loss is the number one reason most people try intermittent fasting.

Some people claim Intermittent Fasting helps you lose weight because you naturally eat fewer calories during your “feeding window”. Others claim intermittent fasting boosts your metabolism or enhances fat burning.

The truth? It’s a bit of both. Science tells us that intermittent fasting is a very powerful weight loss tool that works because you not only eat fewer calories but also because it changes how your body processes those calories.

We know that intermittent fasting lowers insulin and increases growth hormone levels. Because of these two functions, intermittent fasting increases the release of the fat-burning hormone norepinephrine (noradrenaline).

This study found that short-term fasting increased your metabolic rate by 3.6%, while other studies have suggested that short-term fasting increases metabolism by 14%. Both studies linked the metabolic increases to the changes in hormones caused by fasting.

Intermittent fasting can also work by naturally encouraging you to eat fewer calories. When you stop eating at 7 pm, for example, you might skip a late-night snack or midnight meal. That’s 200 to 500 calories per day that you’re not consuming, which is inevitably going to lead to weight loss over time.

This study, for example, described intermittent fasting as “an option for achieving weight loss and maintenance” because IF led to reduced calorie consumption over traditional calorie-restricted diets. That study was published in the International Journal of Obesity in 2005. Researchers also praised intermittent fasting for its long-term adherence, ability to meet minimal nutritional requirements, and its ability to promote loss of fat and preserve lean muscle mass while delivering “sustained beneficial effects on metabolic and disease markers.”

What about the long-term weight loss effects of intermittent fasting? Does the weight loss actually last? This 2014 review study looked at all major studies on intermittent fasting and found that IF led to a weight loss of 3 to 8%, on average, over a 3 to 24 week period, which is a significant amount of lost weight compared to most diet plans.

That same review study also found that people lost 4 to 7% of their waist circumference, on average, while following an intermittent fasting plan. That means significantly less disease-causing belly fat accumulation around your crucial organs.

Of course, critics may claim that intermittent fasting can also lead to muscle loss. Your body’s muscles need calories to survive. Is this weight loss coming from lost fat or lost muscle? This study examined the muscle loss incurred while following an intermittent fasting plan and found that IF led to less muscle loss than a typical calorie-restricted diet plan.

Overall, however, it’s important to remember that most of the weight loss effectiveness of intermittent fasting comes from the fact that you’re eating fewer calories overall. If you spend your “fasting” window eating junk food because you’ve been starving for 16 hours, then it’s unlikely that IF will be successful, and most studies support this.

What about other benefits? As mentioned above, multiple studies have reinforced the idea that intermittent fasting can enhance levels of human growth hormone (HGH). In fact, this study suggested that HGH levels increased as much as 5x while following an IF routine. Higher levels of HGH are linked to increased fat loss and improved muscle gain, among other benefits.

This study specifically analyzed the effects of HGH on men over 60, stating that male HGH levels naturally decreased with age and that lower HGH levels corresponded to decreased lean muscle mass, the expansion of adipose fat tissue, and the thinning of the skin.

This study also showed that higher HGH levels caused by fasting improved muscle strength, maximum oxygen uptake during a treadmill test, although this effect was more significant in men than women.

To sum up, human growth hormone plays a crucial role in multiple aspects of physical performance, and fasting raises levels of HGH by up to 5x according to multiple peer-reviewed studies. Yes, weight loss is a crucial benefit of intermittent fasting, but the apparent benefits of HGH cannot be overlooked.

Intermittent fasting improves insulin sensitivity, causing insulin levels to drop dramatically. When your body has lower levels of insulin, it makes body fat more accessible. As this study indicated, low insulin levels send a signal to your body to start burning fat.

What about cellular repair? Does fasting really help your cells repair themselves? Multiple studies, including this study and this one, have shown that intermittent fasting can encourage autophagy, which is the process where your cells digest and remove old and dysfunctional proteins that build up within themselves. This is a crucial part of cell repair (and overall body repair) and it’s done when your body is fasting.

Intermittent fasting also seems linked to gene expression. IF could change the function of genes related to longevity and disease protection. This study published in Current Opinion in Oncology in 2013, for example, showed that fasting could improve anti-cancer activity within the body and reduce the risk of cancer. This study, meanwhile, described caloric restriction and intermittent fasting as “two potential diets for successful brain aging” because of the effects these diets had on gene activity.

Based on the results of the two studies linked above, intermittent fasting seems to, quite literally, change the function of your genes to enhance your longevity and protection against disease.

Speaking of anti-cancer benefits, certain animal studies have shown that intermittent fasting may prevent cancer.

In this study published in Cancer Investigation in 1988, researchers found that the survival of tumor-bearing rats was enhanced when they followed a calorie-restricted diet. A similar study published in 2012 argued that “short-term starvation (or fasting) protects normal cells, mice, and potentially humans from the harmful side effects of a variety of chemotherapy drugs.”

One of the most significant studies on the anti-cancer benefits of intermittent fasting, however, was published in 2002. In this study, researchers found that intermittent fasting had an “anti-promoting effect” on the growth of tumors in mice. All three of the anti-cancer studies linked were done on animal models (mice and rats) and not humans.

Other studies have shown that fasting can reduce inflammation. Research increasingly reveals the connection between inflammation and disease: inflammation is a key driver of disease, and anti-inflammatories may be able to reduce your risk of disease. In this study published in 2007, researchers found that “alternative day calorie restriction” improved clinical findings and reduced markers of oxidative stress and inflammation in overweight adults. In other words, intermittent fasting or calorie-restricted diets reduced inflammation in an at-risk population.

This study published in 2007 specifically studied the effects of Ramadan fasting on the human body. Researchers concluded that prolonged intermittent fasting in a model like Ramadan “had some positive effects on the inflammatory status of the body and on the risk factors for cardiovascular diseases.” This study published in 2012 by researchers in Saudi Arabia, meanwhile, echoed these findings, showing that “Ramadan Intermittent Fasting” or “RIF” suppressed inflammation while also decreasing body fat.

Many of these studies have hinted towards the cardiovascular benefits of fasting. However, several studies have specifically linked fasting to cardiovascular benefits including reduced levels of “bad” LDL cholesterol, blood triglycerides, inflammatory markers, blood sugar, and insulin resistance, all of which are risk factors for heart disease.

This study published in the American Journal of Clinical Nutrition in 2009, for example, showed that short-term modified alternate-day fasting was “a viable diet option to help obese individuals lose weight and decrease CAD [coronary artery disease] risk.”

This study from 2013 echoed those results. After analyzing available studies on intermittent fasting, researchers declared that “IF has recently been shown to have a positive impact on cardiovascular health”. Researchers cautioned that most studies were small and that further research was required to support these claims, but early results were promising.

There is also evidence that intermittent fasting reducing the effects of aging in a variety of ways. This study published in 2005, for example, aimed to evaluate how intermittent fasting affected age-associated disorders in mice. Researchers found that “alternate fasting could exert a beneficial antioxidant effect and a modulation of the oxidative stress associated with aging.”

The anti-aging effects of intermittent fasting were also observed in this study published in Gerontology in 1982 where researchers found that rats following an intermittent fasting diet lived 75% longer than a control group.

These results were echoed in this study published in 2000 where the mean survival time of rodents increased significantly with intermittent fasting. Researchers concluded that “fasting mice survived significantly longer than the full-fed mice, in spite of the fasting group having a heavier body weight than the control group…short-term repeated fasting manipulation was also effective on the prolongation of life-span in autoimmune-prone mice.”

Based on these two studies (again, which were on mice and not humans), intermittent fasting seems to have significant anti-aging benefits.

Overall, most people engage in intermittent fasting because of the weight loss benefits. As the studies above show, however, intermittent fasting eating systems seem to have significant other benefits as well; including reduced inflammation, improved heart health, improved brain health, anti-aging, and anti-cancer, among other benefits.

Who Should Follow an Intermittent Fasting Plan? Who Should Not Follow IF?

Intermittent fasting plans appear to help certain people achieve certain health goals. If you want to lose weight or reduce your risk of disease, for example, then it seems intermittent fasting may be helpful. However, intermittent fasting is not recommended for anyone who is underweight or has a history of eating disorders.

Additionally, growing research suggests women may not benefit from intermittent fasting as much as men. This study, for example, showed that intermittent fasting improved insulin sensitivity in men but worsened it in women.

Animal studies have also indicated differences in the way female bodies handle intermittent fasting compared to male bodies. In this study and this study on rats, for example, researchers found that intermittent fasting made female rats emaciated, masculinized, and infertile and caused them to miss cycles.

Online, you can find anecdotal reports of women reporting similar issues. Some women claim their menstrual periods stopped when doing intermittent fasting, for example, and then returned when they resumed a normal eating pattern.

Ultimately, everybody is different. If intermittent fasting doesn’t feel right for you, and if you start to notice negative side effects, then you should stop. As with anything, we recommend speaking to a doctor before you start an intermittent fasting routine.

Is Intermittent Fasting Safe?

Intermittent fasting seems to be safe and well-tolerated in most studies to date. The most significant side effect of IF is increased hunger.

Some people may also take some time to adjust to the lower caloric intake. You might feel physically or mentally weak, for example, or mentally foggy. Others, however, claim they feel more energized from IF, so your mileage may vary.

Anyone with a medical condition needs to consult with a doctor before starting an IF system. This is particularly important for anyone in the following categories:

  • Diabetics
  • Anyone with low blood pressure
  • Anyone with problems with blood sugar regulation or insulin sensitivity
  • Anyone taking medications
  • Anyone underweight
  • Anyone with a history of eating disorders
  • Females with fertility issues
  • Women trying to conceive
  • Women who are pregnant or breastfeeding

Overall, however, intermittent fasting has an outstanding safety profile. Few studies have indicated any major side effects in healthy adults. Your chances of side effects are minimal when following a 16/8 fasting/feeding routine, although your chances may increase with more extreme IF patterns (like OMAD systems).

Frequently Asked Questions (FAQs) About Intermittent Fasting

Below, we’ll answer some of the most common questions we receive about intermittent fasting.

Q: Can I drink anything during a fast?

A: Typically, most fasts allow you to drink water, coffee, tea, and most other non-caloric beverages (some even drink diet soda). However, you should not add sugar, cream, or milk to your coffee or tea for a true fast (although small amounts might be okay). Many intermittent fasters will only drink water during a fast and will not drink any coffee, tea, or other zero-calorie beverages, and that’s okay too.

Q: I thought it was bad to skip breakfast?

A: Skipping breakfast is one of the most polarizing debates within the health community. Some people claim skipping breakfast is unhealthy and that breakfast is the most important meal of the day. Others argue that by pushing back your breakfast to 10 am or 11 am, you can enjoy the benefits of intermittent fasting. Part of the problem is that the people who skip breakfast, say, a busy parent or worker, already have an unhealthy lifestyle.

Q: Am I losing weight because of fewer calories or because of something else?

A: Studies have shown that intermittent fasting tends to lead to lower calorie consumption. When you only eat during a specific window, you’re naturally going to consume fewer calories. This will typically lead to weight loss. However, some studies have also shown that other factors are at play, like that intermittent fasting can increase your metabolism, encourage your body to burn stored fat, and improve insulin sensitivity, among other benefits.

Q: Can I take a supplement during a fast?

A: Some intermittent fasting advocates say it’s okay to take a supplement during a fast, say, something like a vitamin or mineral. Others abstain from any nutrient intake during the fast.

Q: Should I work out while fasting?

A: When you work out while fasting, your body needs to get its energy from somewhere. If your body doesn’t have food energy (like carbs) from a recently-consumed meal, then it needs to burn fat for energy. For that reason, many people recommend cardio workings while fasting to maximize fat burning.

Q: Does intermittent fasting lead to muscle loss?

A: Most calorie-restricted diets will lead to some amount of muscle loss. When your body is losing weight, it draws energy from everywhere including fat and muscle. However, in this study and others, intermittent fasting was shown to cause less muscle loss than a traditional calorie-restricted diet.

Q: Will fasting cause my metabolism to slow down?

A: There’s a prevalent myth among IF critics that fasting causes your metabolism to slow down. Contrarily, studies have shown that short-term fasting boosts metabolism. However, long-term fasts (more than 3 days) have been shown to suppress metabolism. A three-day fast is not a common type of IF system.

Q: What is the most popular type of intermittent fasting system?

A: The most popular IF system is a 16/8 system where you fast for 16 hours and have an eight-hour feeding window. You might have your last meal at 7 pm, for example, and then break your fast with an 11 am meal the next day.

Q: What is OMAD?

A: One Meal A Day (OMAD) is a type of intermittent fasting system where you eat one big meal per day. This may also be known as a 23/1 intermittent fast. Your body is fasting for 23 hours and you have a one-hour feeding window.

Q: What should I eat during my feeding window?

A: One of the advantages of intermittent fasting is that you can continue to eat the same foods you always eat. If you want to maximize fat loss and health benefits, then you should eat a healthy diet. However, intermittent fasting is not technically a diet: it’s an eating pattern.

Q: How does Ramadan intermittent fasting (RIF) work?

A: Ramadan intermittent fasting, sometimes abbreviated to RIF, is a more intense version of an intermittent fasting cycle. During the month of Ramadan, Muslims are forbidden from letting anything enter their bodies. That means from sunrise to sunset, Muslims following Ramadan cannot eat, drink, smoke, or engage in any sexual activity. Even hardcore intermittent fasting advocates will drink water during a fasting cycle. Some research has shown that this extreme style of intermittent fasting can lead to certain health benefits, although it’s unclear if RIF is more effective than traditional IF.

Q: How does eat-stop-eat intermittent fasting work?

A: Under an eat-stop-eat intermittent fasting system, you fast for 5 days a week and have a calorie-restricted day twice a week. This is called a 5:2 intermittent fasting system. Some people completely fast on their fasting days, while others maintain a reduced daily caloric intake of 500 to 700 calories.

Q: Should everyone fast?

A: Fasting isn’t for everyone. With some people, like those who are underweight or have an eating disorder, fasting can be dangerous. With others, like women who are trying to become pregnant, fasting could cause fertility issues. Generally, intermittent fasting has been proven safe in most studies, although we still recommend talking to your healthcare professional before you fast intermittently.

Final Word on Intermittent Fasting in 2023

You already intermittently fast without knowing it: your body is fasting when you fall asleep at night. If you’ve ever skipped dinner or breakfast, then you might have gone 12 or 16 hours in “fasting” mode without even trying to fast intermittently.

Most people intermittently fast for weight loss. However, as the research above indicates, intermittent fasting can lead to other surprising benefits, including improvements in heart and brain health, reduced risk of disease, anti-aging boosts, and a reduced risk of cancer, among other benefits.

We will update our Advanced Living 2023 intermittent fasting review guide with the latest research advancements, scientific studies and medical health discoveries associated with the trending IF diet once available.

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