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Before changing the way you eat and altering your diet in any significant way, please speak with a health professional to make sure it’s the best decision for you.

“OMG, have you tried this new intermittent fasting thing, my lovelies? It’s like a fancy version of skipping breakfast. #DietLife #LookinGreat #FeelinGreat #InsufferablySmug”

We’re sure you know all about the intermittent fasting (IF) weight loss buzz from your friends at the gym or the posts you (very quickly) scroll past on your Insta feed (seriously, eff that ingratiating individual and their perfect hair).

But what is intermittent fasting? And how do you make it past 10 a.m. without eating and avoid the urge to rip someone’s chin off in a hangry rage?

Here’s everything you’ll need to know before heading into the unknown.

Fasting is nothing new. Our ancestors did it (because they didn’t have constant access to food) before anyone ever muttered the words “skinny jeans,” “thigh gap,” or “cleanse” (or any words at all, for that matter).

Countless religious ceremonies revolve around some form of dietary fast — from the 25-hour Jewish fast of Yom Kippur to the month-long daytime fast of Ramadan in Islam.

Today, it’s not so much used by the masses as an enlightening or spiritual experience. Many people use IF to restrict calories and manage their weight, but not everyone uses it to support weight loss alone.

IF involves alternating cycles of abstaining from eating food. Sounds simple enough, right? We basically do that every day anyway when we go to bed and wake up, hence break-fast (😱😱😱).

While most types of IF don’t dictate which foods to eat or even how much to consume, it’s definitely a little more structured than just deciding to eat and then deciding to stop. The success lies in the consistency.

During the fasted period, whatever the length may be, no food should grace your lips.

You are, however, allowed to drink water, tea, coffee, and other noncaloric beverages (so no, a Grande Frappuccino doesn’t fly, sorry).

Today, IF has been adopted by health and wellness gurus all over the world, each of whom advocate a specific IF regimen.

That’s because, on the whole, it works. A 2020 review that included 27 IF trials found that the programs led to weight loss of 0.8 percent to 13.0 percent of baseline weight without serious side effects in every study.Welton S, et al. (2020). Intermittent fasting and weight loss. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/

Was it any better for weight loss than traditional calorie restriction, though? Not really.

This may have as much to do with the flexibility of the regimen and the relative freedom of food choice when compared with other diets — the keto diet, for example, can be highly restrictive. And who doesn’t love a carb or two?

One of the great aspects of IF is it’s flexible. As IF isn’t one-size-fits-all, you can find a way to make the regimen fit with your lifestyle.

After all, if eating a certain way makes you feel like sh*t, there’s no point in doing it. Yes, they will challenge you in the beginning, but you also have a life to live and you should feel good.

So try one of these that looks doable. If it doesn’t work, but you’re still up for another, try a different method. There are many types of IF eating patterns, and some are more restrictive than others. Here are some of the most popular.

12/12 Method

This is a beginner’s IF regimen. And you’re probably doing something very similar every day without even thinking about it.

This method involves fasting for 12 hours a day and eating within a 12-hour window. If you eat your last meal at 7 p.m. and have breakfast the next morning at 7 a.m., congratulations, you’re already an IF ninja.

16/8 Method

With this IF method, you fast for 16 hours each day and restrict your eating window to just 8 hours, which likely means you can squeeze in two, maybe three meals.

Depending on when they stop eating the night before, most people following the 16/8 method simply skip breakfast, have their first meal midday, and refrain from eating too late at night.

You’re still allowed a black coffee to get your gears running in the morning, if this sounds like a struggle.

20:4 Method

Here’s where it’s getting a bit more intense. Now, you’re fasting for a full 20 hours and allowing yourself one 4-hour window to eat. It’s likely you might get just one, maybe two meals in each day, depending on what works for you.

Steel yourself before embarking on this one. Keep in mind that this is an extreme type of IF because it cuts down your eating window significantly.

Modified alternate day fasting

In this more extreme “alternate-day fasting” (ADF) method, you’re severely restricting calories 2 days of the week (to around 500 calories each day) and eating regularly on the other 5 days.

However, it’s not as intense as the unmodified version, so it may be more comfortable to adopt.

According to a study from 2020, a modified ADF eating pattern led to more weight loss than a traditional calorie restriction diet.Razavi R, et al. (2020). The alternate-day fasting diet is a more effective approach than a calorie restriction diet on weight loss and hs-CRP levels. https://pubmed.ncbi.nlm.nih.gov/32003649/ It works — but it’s also hard work.

Just avoid jumping straight into it and work your way up through whatever feels most comfortable.

Eat-stop-eat

Like the 5:2, this ADF method doesn’t provide a consistent daily fast schedule, but rather allows you to choose 1 or 2 days in the week to have a full 24-hour fast.

TBH, this one sounds like pure hell.

Making a plan more flexible means that you’re more likely to stick to it. That’s the really important factor of any health-based lifestyle change — consistency. If you can do something every day or week, you’ll really start to see the benefits pile up.

We took a more in-depth look at the benefits of fasting here.

1. You eat less

This may be the only benefit you came here for — IF as an aid for weight management.

But does it actually work? Well, it probably will. Since the purpose of IF is to restrict your window of eating, it’s likely you’ll eat fewer meals, and assuming you don’t binge during your “feasting” window, you could well lose weight.

One study from 2016 compared a high-protein, reduced-calorie IF regimen with a traditional heart-healthy diet plan.Zuo L, et al. (2016). Comparison of high-protein, intermittent fasting low-calorie diet and heart healthy diet for vascular health of the obese. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5002412/

The researchers found that while the different groups lost similar amounts of weight, the IF had a bit of an edge for minimizing weight regain after one year (See? Consistency. Don’t say we didn’t warn you).

Another study found that IF was as effective as daily caloric restriction for weight loss.Rynders CA, et al. (2019). Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6836017/

If you want to eat less, we explain how to stop feeling hungry all the time.

2. It keeps your brain sharp

We all want to keep our thinking caps as ready to tip as possible, and IF may help.

A review from 2018 suggested that IF may help your cogs turn.Mattson M, et al. (2018). Intermittent metabolic switching, neuroplasticity and brain health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5913738/ The researchers put forward that undergoing a metabolic challenge which induces fat burning, such as fasting, followed by a recovery period, can support brain health throughout your lifespan.

This means IF not only supports how the brain works, but may also help that wrinkly marvel in your skull to keep damage and disease at bay.

Other studies suggest that IF may helps the following:

  • preventing short-term and special memory loss (however, bear in mind that the study used rodents)Shin BK. (2018). Intermittent fasting protects against the deterioration of cognitive function, energy metabolism and dyslipidemia in Alzheimer’s disease-induced estrogen deficient rats. https://pubmed.ncbi.nlm.nih.gov/29307281/
  • reducing brain damage and functional impairmentArumugam TV, et al. (2011). Age and energy intake interact to modify cell stress pathways and stroke outcome. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844782/mediating the severity of Alzheimer’s in rats

While we’re still waiting on the credible studies on humans to draw any solid conclusions, it’s definitely some good food for thought — or a temporary lack of food that helps thought, anyway.

IF is certainly not the only option for boosting your brainpower, though.

3. It helps reduce the risk of diabetes

Reducing the risk of diabetes has always been top of mind for most public health professionals, and it’s looking like IF may play a role.

A recent review of the literature found that IF helped reduce visceral belly fat, fasting insulin, and insulin resistance in overweight and obese populations as effectively as a more traditional diet that simply restricted calories.Barnosky AR. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. https://www.sciencedirect.com/science/article/abs/pii/S193152441400200X

IF can also help people control their blood sugar, which can be an important tool in your quest to prevent or control diabetes.Cho Y. (2019). The effectiveness of intermittent fasting to reduce body mass index and Glucose metabolism: A systematic review and meta-analysis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6832593/

So, if a fasting regimen is more sustainable for you than consistently cutting calories, combining IF with a healthy diet and lifestyle may well help you keep diabetes from the door.

Although IF may be helpful for some people with high blood sugar, it’s not the best choice for others. Make sure you check in with your healthcare provider before trying IF if you have diabetes.

4. It might help maintain a healthy heart

Some researchers advise that IF may just help your ticker keep ticking. However, findings are mixed, so more research is needed to put this forward as a bona fide prevention for heart problems.

A 2018 review of studies on IF’s heart health impact suggested that it may help reduce several risk factors for heart disease, including blood pressure, triglyceride levels, and cholesterol levels.Ganesan K, et al. (2018). Intermittent fasting: The choice for a healthier lifestyle. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128599/

It’s unclear as to whether the benefits come from weight loss or other mechanisms, according to a different review.Malinowski B, et al. (2019). Intermittent fasting in cardiovascular disorders: An overview. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471315/ The review also says that, despite its many benefits, IF may also increase the risk of heart problems when older adults give it go.

There’s plenty of research out there suggesting that IF may benefit heart health. However, we definitely need larger randomized control trials to see how IF can improve heart health.de Cabo R, et al. (2018).
Intermittent fasting and cardiovascular disease: Current evidence and unresolved questions. https://pubmed.ncbi.nlm.nih.gov/29199853/

These are the best foods for your heart.

5. It might help reduce chemo side effects

Research on the links between IF and cancer is dicey and currently limited to rat models. This isn’t a fantastic indicator of what will happen in the human body (even though though the lead in Ratatouille is a fantastic indicator of what will happen to human food if a rat gets involved).

However, there’s promising signs in recent research that IF may help improve how effective chemotherapy can be as well as reducing its toxicity across the body.de Groot S, et al. (2019). Effects of short-term fasting on cancer treatment. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6530042/

Researchers hypothesize that, as metabolism plays an important role in how tumors develop, short term fasting may improve how chemotherapy acts on tumors (although they maintain that large clinical trials should take place to back this up).Zhang J, et al. (2020). Fasting to enhance cancer treatment in models: The next steps. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7201989/

We found 15 foods that may help you reduce the risk of cancer.

It’s not all roses when it comes to IF. Yes, it has benefits, but it does carry a few risks.

1. It could impair athletic performance

Getting the most out of your workout comes down to carefully timed fuel. Restricting calories for long periods of the day may well get in the way as you could be running (literally) on half a tank.

Not only can it leave you too sluggish to really push the pedal to the medal, but if your workout isn’t timed perfectly during your “feasting” phase, you could be missing out on a really important window for muscle growth and glycogen replenishment.Aragon A, et al. (2013). Nutrient timing revisited: Is there a post-exercise anabolic window? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3577439/

Combining the right diet with regular exercise can help you shape up.

2. It’s not realistic in the long run

IF can be really hard to stick with in the long run.

One study actually compared IF to daily caloric restriction and found that the dropout rate was higher among fasters than calorie-cutters.Trepanowksi FJ, et al. (2013). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: A randomized clinical trial. https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/2623528?redirect=true

This study looked at ADF — one of the most restrictive types of IF. Other types of IF, such as 16/8, may be easy to follow on a long-term basis.

Interestingly, this study also suggested that the individuals assigned to the fasting group gradually just ended up cutting calories over time. Calorie-cutting may just be a more natural way to eat.

With this being said, the range of IF plans available should mean that most people can find an option that’s comfortable for them. Over time though? Any change to your eating pattern can be challenging.

3. It could contribute to disordered eating

While it’s not officially documented, it’s very easy for people in the “diet mindset” to overdo their “feast” phase.

In other words, if you get free rein to eat whatever you want for a few hours and you’re hangry when you get there, it’s not unreasonable to assume you’re going to face plant into the first thing you see. (Hello, office donuts!)

Not only will this negate any weight-loss benefits, but it’s also possible it can lead to some binging behaviors over time.

However, there’s evidence to suggest that IF does not significantly affect the symptoms of those with eating disorders.Gabel K, et al. (2019). Safety of 8-h time restricted feeding in adults with obesity. https://pubmed.ncbi.nlm.nih.gov/30216730/ A different study from 2015 suggested that the effects of IF could even benefit those who engaged in disordered eating.Hoddy KK, et al. (2015). Safety of alternate day fasting and effect on disordered eating behaviors. https://pubmed.ncbi.nlm.nih.gov/25943396/

Here’s how to tackle bingeing if you get into the mindset.

4. More research is necessary

So the preliminary research we have sounds promising, but there’s still a really long way to go. Most of the studies we do have are on animals, and our human trials are generally very small.

Also, no one has studied the long-term effects of IF. We don’t know for sure if there are any dangers or major benefits for dieters eating this way in the long run.

If you want to give it a go, it may be best to try IF short-term and see what works for you.

As you can see, there are lots of different methods of varying difficulty when it comes to IF. It’s not a one-size-fits-all diet.

Considering the benefits and risks, IF may be best for people who enjoy a wide range of foods and who struggle with diets that restrict certain types of food groups or macronutrients.

With IF, the focus isn’t on the quality or even the quantity of food you’re eating, rather just the time frame that you’re eating in. So, if you want to keep pasta, chocolate, and wine on the table while potentially promoting weight loss, it may be a palatable option.

IF may also be helpful for those who tend to have digestive problems at night time, as making the last meal of the day earlier may help prevent heartburn, acid reflux, and other digestive woes at bedtime.

While early research suggests that fasting may have some benefits on blood sugar control, individuals with insulin-dependent diabetes should likely avoid radical fasting regimens.Barnosky AR, et al. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. https://www.sciencedirect.com/science/article/abs/pii/S193152441400200X

Enjoying regular, healthy meals can help prevent blood sugar spikes and dips that can be life-threatening for people if not controlled. It may also not be ideal for amateur or professional athletes who depend on perfectly timed fuel before and after activity for athletic performance and recovery.

Another review suggests that children and women who are pregnant or breastfeeding should avoid an IF regimen.Malinowski B, et al. (2019). Intermittent fasting in cardiovascular disorders: An overview. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471315/

We took a closer look at the .

We’re still really just scratching the surface of how IF can support overall health and weight management. It might work for one person but provide no solutions for another.

If you’re looking to get started in IF, it’s best to speak to a registered dietitian and your doctor, who can walk you safely through the best regimen for you. They can also make sure you’re getting all of the necessary nutrients you need during feast time.

Here are the foods it’s best to make the staples of your feasting hours.