Intermittent fasting (IF) is currently among the common dietary trends you see nowadays. And while it isn’t a diet in itself, but rather, a meal timing approach, it’s surprisingly an effective way to lose weight, stay healthy, and live simply.
But how do you practice it correctly, and safely?
This guide will teach you everything you need to know about intermittent fasting: how to practice it, the benefits & safety, and commonly asked problems.
A) What is intermittent fasting?
As mentioned earlier, IF is not a diet in itself, but a specific meal timing protocol.
What does that mean?
It means that each of your meal is eaten within a specific time frame (i.e. within 6-8 hrs).
Unlike popular diets where food components are set at specific macronutrient ratios (such as the ketogenic diet where it’s comprised of high fat and moderate amounts of protein), IF on the other hand, is limited to fasting and feeding windows with no rules on macronutrient intake (provided of course, it’s your personal choice to follow a high fat – low carb meal plan).
Intermitent Fasting Variations
There are various IF variations you’ll often hear, and choosing the best fit for you will greatly help in avoiding common pitfalls and make the journey pleasant.
Here are 4 common variations you’re free to choose depending on your personal schedule and capability:
1) 5:2 Diet
The 5:2 diet (a.k.a. The Fast Diet) is a fasting approach popularized by Medical Journalist Michael Mosley, which consists of 5 days of regular maintenance and 2 days of fasting.
During the 5 days of maintenance, you’re free to eat like any normal day. But mind you, if you think a day of normal meals means binging on fast food you’re probably getting the wrong idea. In this article, or in any other healthy lifestyle for that matter, normal days mean home-cooked food or at least average servings of whole foods that help you keep your current weight. This can range from salads, fish, lean meat, legumes, etc.
In short, whatever type of food helps you stay at your current weight – it’s the one you should stick to.
While for 2 days – you fast.
Obviously, for some people, 24-hour food abstinence may work, but in this diet, you’re allowed to eat roughly 500 to 600 calories during the fasting day. This will equate to a low-fat meal with high protein and moderate amount of carbohydrates.
A good example is a serving of baked potatoes with grilled chicken and a tablespoon of olive oil. You can even replace it with a sandwich of your own liking.
Just make sure to count those calories well.
In this variation, you’re free to choose whichever day you decide to fast as long as there’s a non-fasting day in between (i.e. Tuesdays and Thursdays or Mondays and Fridays).
2) Eat Stop Eat (fast once or twice a week)
Eat Stop Eat is another variation popularized by Brad Pilon, which is very similar to the 5:2 diet. The only difference is you can fast 24 hours instead of eating 500-600 calories on fasting days.
Although it may sound a little bit hardcore, it isn’t that difficult to follow. In fact, you’ll end up eating something each day.
For example, on non fasting days your last meal may be at 8pm, then the next one at 8pm the following day. This helps you keep a 24 hour fast without feeling food deprived, especially at night.
You can opt to fast once or twice a week, again, depending on your personal schedule and preference. But remember to always keep your regular days, regular (no binging on junk/fast food as it can defeat the purpose of fasting, and ultimately lose weight).
3) Alternate Day Fasting (ADF)
In alternate day fasting you basically fast every other day.
During fasting days, you can either abstain from food for 24 hours or eat up to 500-600 calories. While on non fasting days eat double the amount of calories to make up for the deficit lost the previous day (provided it’s not beyond maintenance level). While it may sound nice to be allowed to eat double the amount of meals in 24 hours, in reality it’s quite hard to eat such volume within a day, especially using whole foods, therefore leading to weight loss.
However, be mindful that this approach may put you at risk of developing habits of over eating. Thus making you regain the lost weight or even add extra weight if you ever decide to return to a normal eating pattern.
So unless discipline is something you haven’t yet developed, this variation is not recommended. But if you have, then it’s going to help you stay fit while still enjoying your favorite food every other day.
4) 16:8 Diet
The 16:8 approach is composed of 16 hours of food abstinence and 8 hours of feeding every day (you may even modify it to 20:4 – 20 hours of fasting and 4 hours of feeding.
So far, this is the most used variant and is also perfect for beginners. As it consists only of 16 hours of fasting (basically skipping breakfast and turning lunch into the first meal of the day), which is something that most people unknowingly do, and 8 hours of feeding, thus providing you ample time to eat 2 large and satisfying meals for lunch and dinner (especially if eating out with family or friends).
Some people even stretch it to 20 hours of fasting, hence ending up with 4 hours of feeding (usually at night). But unless you’re pretty used to not eating a single meal for a whole day, a 16:8 approach would be a better option, especially if it’s your first time (you can even begin with 14:10 for the first few days and then work your way up to 16 in a matter of weeks just to get your stomach cells adapt to this eating pattern).
5) Warrior Diet
The warrior diet was popularized by Ori Hofmekler, an ex-israeli soldier who specialized in human biology.
In this variant, fasting and non fasting periods occur every day. The former throughout the day and the latter at night. During the day however, unlike other IF variations where food isn’t allowed, small amounts of low glycemic food, protein, or even fat is allowed (i.e. a small egg, a handful of berries nuts, or a small serving of greek yogurt).
The purpose of the fasting period (Ori calls this “undereating phase” in his book “The Warrior Diet”) is to detoxify and replenish the body with vitamins, minerals, and probiotics. In addition, keeping food intake really low and limiting it to very light servings of fruits throughout the day will help in providing your digestion some rest from larger meals eaten every 3-5 hours.
While at night, well… is the time to treat yourself with a big feast of whole foods (and perhaps a slice of cake).
B) Potential Benefits
Aside from weight loss, IF also brings a number of health benefits. Here are a few of them:
(If you want to a more in-depth topic check out our article entitled “The Effects of Fasting on Your Body”)
1. Enhances your metabolism
Metabolism is a term used to describe chemical reactions that maintain the present state of cells and living organisms. In the realm of dieting however, metabolism pertains to how your body handles energy sources, particularly carbohydrates and fat. When it slows down, it puts you at a higher tendency to gain fat, when it goes up, it helps you lose weight.
The benefit about IF is that metabolism is enhanced, therefore, prompting your body to lose more weight rather than gain it (provided of course, caloric deficit is achieved).
2. Enhances Protective Mechanisms Against Oxidative Stress
Oxidative stress is an imbalance between antioxidants and free radicals in your body, which is caused by an increase in Reactive Oxygen Species (unstable molecules that can damage our DNA, leading to various diseases).
Fasting on the other hand tends to increase the body’s response against oxidative stress through a number of defensive mechanisms, therefore placing you at a lower risk of acquiring lifestyle related disease.
3. Protects From Tumor Growth
Oncogenic mutations (mutations in the DNA that lead to cancerous cells) are the etiologic reason of how cancers develop.
Research has shown that fasting decreases the incidence of cancer, in fact, a number of animal studies have shown potential for decrease in tumor growth in conditions such as melanoma, neuroblastoma, and breast cancer.
4. May Increase Lifespan
While prolonging lifespan has been a long sought out mystery for scientists, fasting has been shown to promote that ability across different lifeforms.
This is due to different mechanisms, such as lengthening of telomerases (caps of DNA that protect your cells from aging), which together with exercise and a healthy diet, provides a way to increase lifespan.
C) Basic Rules of Fasting
Intermittent fasting can be divided into 2 cycles: the fasting and the feeding phase.
A. The Fasting Phase
In this phase, which ranges from 16 to 24 hours (depending on which variation you choose), no regular meals are allowed. At most, calorie free beverages such as tea and coffee (definitely without table sugar or creamer), diet sodas, or even fused water are a good option. They may help control hunger for some and even boost metabolism (especially coffee).
In some variations, such as the Warrior Diet, small amounts of low glycemic fruits are acceptable (i.e. berries), at most a small boiled egg is another alternative if you really need something under your mouth at noon time.
Buf if you decide to follow variants such as the 16:8 or alternate day fasting, then stick to calorie free beverages throughout this phase. And obviously, lots of water too.
B. The Feeding Period
During the feeding phase you’d want to stick to as much whole food as possible and minimal processed food (a slice of cake for dessert or any delicacy of your choice is acceptable), hence the reason for cooking your own food at home.
A good trick to easily get satiated is eating carbodyrate sources such as yams, potatoes, or legumes combined with a good amount of protein, fruits and vegetables. Then, ending with your favorite dessert of choice.
Keep in mind that ideally you should be counting calories to keep things efficient. But if you’re not a lover of doing computations for each meal, then stick to food servings and eyeballing. Whole foods with high protein and fiber are enough to make you satiated without overeating.
Also, if you’re following a 16:8 approach, keep your feeding phase with 2 large meals maximum (i.e lunch and dinner) or 1 big feast for a 20:4 warrior diet variant. Try to minimize snacks in between if you’re not into calorie counting. This will make sure that you’ll keeThe Feeding Periodp yourself at a caloric deficit (the most important principle of any weight loss diet).
D) Safety and Side Effects
While fasting is surprisingly an effective method for losing weight, it’s not a one size fits all approach. In fact, symptoms of a number of diseases may worsen under physiologic stress induced by fasting, hence highlighting the importance of approval from a qualified professional.
Here are common conditions that need supervision from your local physician:
1. Anorexia Nervosa
Anorexia Nervosa, an eating disorder that has the potential to be life threatening. As this is characterized by individuals with a devastating fear of weight gain and dietary habits that prevent weight gain (e.g. following a very low calorie diet ranging from 300-500 calories a day), it’s a safety precaution that people affected by this disorder should abstain from intermittent fasting, unless it has been managed by a healthcare professional.
2. Bulimia Nervosa
In contrast to Anorexia Nervosa, Bulimia Nervosa is characterized by recurrent episodes of binge eating accompanied by a sense of loss of control. Followed by inappropriate compensatory behavior to avoid weight gain such as self-induced vomiting, abuse of laxatives and diuretics, excessive exercise, and episodes of fasting or severe dieting.
This disorder can lead to an array of symptoms such as dizziness, palpitations, electrolyte imbalance, etc. However, these can be managed once treatment has been started.
3. Diabetes Mellitus Type 2 (DMT2)
Diabetes Mellitus Type 2, a disease characterized by insulin resistance, inappropriate glucagon secretion and decreased production of insulin from the pancreas can lead to various complications.
In the context of fasting, there is evidence of successful weight loss among diabetic patients along with improvement in HBA1C (a marker used to measure DM severity). However, the risk of hypoglycemic episodes also exists, hence the importance of medical guidance.
4. Peptic Ulcer Disease
A condition affecting the lining of the stomach leading to painful sores and ulcers is commonly presented with stomach pain symptoms. It can be caused by different etiologies, but most commonly from drug use (e.g. NSAID), smoking, stress, and bacteria.
Some studies involving individuals with PUD practicing Ramadan show worsening of symptoms during fasting. Therefore, close monitoring from a healthcare professional is also needed.
E) Frequently Asked Questions
1. What is the best time of the day to break the fast?
The best time of the day to break the fast is — anytime, as long as it suits your schedule.
While cortisol levels may be high in the morning, fasting can be broken anytime of the day. This is because the timing of the first meal won’t matter as long as you fast for at least 16 (or 24) hours.
So if abstaining from food from 8pm to 8pm of the next day or 10pm to 3pm of the next day works for you, then that shouldn’t be a problem.
2. What should I eat on non-fasting hours/days?
As mentioned earlier, it would be better to eat whole foods on feeding hours for two main reasons:
One, it will keep you satiated compared to processed food (due to high fiber and protein content), two, you’ll end up eating less calories than you should, resulting in weight loss, and three, it will keep you healthy.
3. How long will it take for my body to adapt?
Adaptation differs for each individual. But expect to get used to it in no less than 3 weeks, as this is the timeframe at which stomach cells take to adjust.
4. Should I still count calories when practicing IF?
Although calorie counting is crucial when it comes to weight loss, it’ shouldn’t necessarily be used for IF. As long as meals revolve around whole foods and servings are appropriately managed (e.g. eating less servings that normal days), weight loss is achievable.
5. Am I allowed to have cheat days?
Cheat meals twice a week help to relieve some mental tension. Also, they prevent metabolic adaption from the constant low calorie intake from fasting.
However, keep in mind that a cheat meal is not a free ticket to an eat all you can buffet, but rather, a simple meal you’ve been craving for the last few days, like 2 slices of pizza or a serving of burger with fries.
6. Is it okay to exercise while fasting?
Yes, exercising while fasting can be done. In fact, it will stimulate better epinephrine and cortisol production leading to enhanced fat loss while maitaining lean body mass.
If exercise on an empty stomach scares you, a scoop of whey protein or a small boiled egg will suffice as a small pre workout meal.
7. How long is it safe to fast?
A limit of 24 hours is acceptable. Even though fasting continously for days have been documented by researchers, the studies were done on obese individuals (the more body fat a person has, the longer it can fast due its greater amount of fat stores used for energy). However, in non obese individuals, the risks of losing lean body mass is greater if prolonged fasting is done. Hence, a limit of 24 hour fast is a good benchmark in this type of dietary approach (after all, the process of losing weight does not need to resort to extreme measures).
8. Will I lose muscle tissue while on IF?
If things are done right, you won’t lose muscle tissue. In fact, well controlled fasting has shown to promote muscle sparing effects. However, it’s important to highlight that in times of chronic stress (e.g. lack of sleep, work, etc), muscle wasting may occur due to high levels of cortisol. And the problem compounds when you add fasting on your schedule.
Hence, it’s important to gauge how your body reacts during fasting, and adjust accordingly whether you need to stop for a few days or not.
9. Can I use sweeteners such as Stevia or Splenda?
Absolutely. What matters greatly in IF is keeping low insulin levels during fasting hours to maximize fat burning. Hence the addition of stevia or splenda in coffee or tea is allowable since these are non insulin stimulating substances.
F) Summary and Conclusion
• While there are a number of variations in intermittent fasting, they all revolve around two phases: fasting and feeding hours.
• The fasting period can last from 16 to 24 hours, while the feeding period from 4 to 8 hours, or in some variations 2 or 3 days.
• During fasting periods calorie free beverages are allowed, such as brewed coffee or tea, but more importantly, lots of water.During the feeding period, mainly stick to whole foods such as yam, potatoes, beans, fish, lean meat, eggs, etc.
• A slice of cake or any dessert of your choice is allowed during feeding windows, provided it’s only a single serving.
• Exercise during fasting is highly recommended. It blunts hunger and enhances fat burning.
• The most critical component to make this weight loss approach effective is staying at a caloric deficit, which can be achieved by eating whole foods due to their satiating effects and lower calorie content compared to processed ones, as well as good amounts of exercise.
While Intermittent fasting is certainly an effective tool for weight loss, the process of adjustment isn’t necessarily easy. But once your body has adapted to the timing of meals, hunger will subside and mental focus increase. And as a bonus, you’ll get to enjoy bigger meals while eating your favorite dessert.