Pros and Cons of 5 Intermittent Fasting Methods
Below we've got a decent intermittent fasting 101 article from Cecilia Snyder, MS, RD and Kris Gunnars, BSc. In addition, if you'd really like to consider doing intermittent fasting right, here's what else you should know:
Dr. Cohen notes most sustainable and repeatable way to intermittent fast is to do it daily on a 8 hour eating window with 16 hour not-eating window. It's also important to note you should ideally finish you last meal 4 hours before bedtime for proper digestion, sleep, recovery, and blood sugar.
Another fasting concept missed in the article is macronutrient fasting and low protein fasting. For example, Dr. Cohen does low protein fasts for just 1 day every now and then, it's his simple longevity biohack to improve autophagy with age.
There's also research on low-calorie fasting for 5 days before you under go surgery for improved recovery. You fast on 80% of your normal caloric intake five days before your surgery date by eating simple but nutrient rich foods (mostly veggies) and then resume normal eating afterwards. Sounds kind of scary, but Dr. Cohen's son has done this fast in the past and came out alright. He says, however, it's not fun at all. :)
If you conduct the warrior fast, make sure your not spiking your blood sugar by snacking on essentially low calorie, simple-carbs. Use the CGM to help guide you.
The authors also forgot the mention the tons of longevity benefits of intermittent fasting.
Calorie counting, for lack of better words, is outdated and just wrong: if you've read any of our articles by now, you know there is much more to calories in vs. calories out for weight and fat management.
As for feeling hungry, it depends on the type of fast you do. If you choose the simple 8/16 intermittent fast, you shouldn't feel hungry at all, even if you are not used to fasting, if you are properly fat adapted (of which a simple test is that you should be able to skip a meal without getting super hungry).
Think of intermittent fasting like cold showers for your diet. They kind of are a little frustrating at first and potentially new and uncomfortable, but over time you experience benefits.
It's true, diet quality and nutrient profiles are most important. And, when in doubt, eat more protein when fasting.
Intermittent fasting has been one of the most popular health trends of the past decade.
Some people swear by the eating pattern, finding that it helps manage their appetite and weight and to support optimal health.
Nevertheless, intermittent fasting might not be right for everyone — either for medical reasons or because it doesn’t match their picture of a nutritious and sustainable diet.
This article takes a closer look at some of the most popular ways to do intermittent fasting, as well as a few pros and cons.
The information may help you decide if intermittent fasting is something you want to try for your health and happiness.
Intermittent fasting is generally considered safe. However, it is best to use caution when beginning or following the eating routine. Restricting your calorie intake for an extended period of time could be dangerous for:
children and adolescents
people who are pregnant or breastfeeding
people who have diabetes
people taking certain medications
people with a history of eating disorders
Before embarking on intermittent fasting or making any other drastic changes to your diet, consult a trusted healthcare professional to help you get started safely.
What is intermittent fasting?
Intermittent fasting is an eating pattern during which you refrain from consuming any calories for an extended period of time. Usually, this period lasts between 12 and 40 hours (1Trusted Source).
Water, coffee, and other calorie-free beverages are allowed during the fast, but no solid foods or calorie-containing drinks are permitted.
For example, if you finish dinner at 7 p.m. Monday and don’t eat again until 7 p.m. Tuesday, you’ve completed a 24-hour fast. Some people choose to fast from breakfast to breakfast or lunch to lunch. But which time frame works best depends on the individual.
A full 24-hour fast every other day can seem extreme and may be difficult for many people to maintain, so it’s usually not recommended for beginners. However, you don’t have to go all-in right away, and many intermittent fasting routines start with shorter fasting periods.
Here are 5 of the most popular eating patterns for adding intermittent fasting to your diet:
Time-restricted eating. Involves fasting every day for 12 hours or longer and eating in the remaining hours. A popular example is the 16/8 method. It features a daily 16-hour fast and an 8-hour eating window wherein you can fit in 2, 3, or more meals.
The 5:2 diet. The 5:2 diet involves eating as you normally do 5 days of the week and restricting your calorie intake to 500–600 on the remaining 2 days.
Eat Stop Eat. Eat Stop Eat involves a 24-hour fast once or twice per week.
Alternate-day fasting. With alternate-day fasting, the goal is to fast every other day.
The Warrior Diet. The Warrior Diet was among the first popular diets to include a form of intermittent fasting. It involves eating small amounts of raw fruits and vegetables during the day and eating one large meal at night.
Intermittent fasting is a dietary routine that regularly alternates between periods of eating and fasting. There are many different methods of doing so, with many requiring you to fast for 12–40 hours at a time.
3 pros of intermittent fasting
Researchers have already linked numerous health benefits with intermittent fasting and continue to examine them.
Plus, for some people, intermittent fasting fits well into their model of a healthy and sustainable long-term diet.
If you’re wondering if intermittent fasting could be right for you, here are a few benefits that might pique your interest.
1. Might support weight loss and improve metabolic health
Two main reasons why people try intermittent fasting are to manage their weight and metabolic health. Metabolic health is a marker of how well the body processes, or metabolizes, energy. It’s often measured by blood pressure, blood sugar, and blood fat levels (2Trusted Source, 3Trusted Source, 4Trusted Source, 5Trusted Source).
Fasting or abstaining from food can create a calorie deficit, meaning that your body has fewer calories than it needs to maintain its current weight. That’s why diets that rely on calorie restriction, like fasting, are the hallmark of most weight loss diets.
Research shows that some types of intermittent fasting can be as effective for weight loss — though not necessarily more effective — as other diets that also rely on limiting your daily calorie intake (6Trusted Source, 7Trusted Source, 8Trusted Source, 9Trusted Source).
Time-restricted eating routines similar to the 16/8 method are one type of intermittent fasting that has been linked directly with weight loss. Alternate-day fasting and the 5:2 diet may also be effective (10Trusted Source, 11Trusted Source, 12Trusted Source, 13Trusted Source).
Besides naturally eliminating your calorie intake during the fasting period, intermittent fasting may support weight loss by regulating your appetite to increase feelings of fullness while suppressing feelings of hunger (14Trusted Source, 15Trusted Source, 16Trusted Source).
The eating pattern has also been linked with other improvements in health, such as:
lowering blood pressure (15Trusted Source, 17Trusted Source, 18Trusted Source, 19Trusted Source)
improving blood sugar (4Trusted Source, 11Trusted Source, 15Trusted Source, 20Trusted Source)
repairing damaged cells (21Trusted Source)
protecting brain health (22Trusted Source, 23Trusted Source, 24Trusted Source)
2. Can be a sustainable lifestyle change
Intermittent fasting might sound complicated and intimidating, but it can be simple at times. In fact, you might even find that fasting helps simplify your day since you need to plan fewer meals.
What’s more, it doesn’t typically require calorie counting, watching your macros, eating certain foods that you might not be used to eating, or eliminating certain foods that you otherwise enjoy.
For example, having an early dinner followed by a late breakfast the next day is one way to fast intermittently. If you finish your last meal at 8 p.m. and don’t eat until noon the next day, you’ve technically fasted for 16 hours.
For people who get hungry in the morning and like to eat breakfast, or for those who can’t eat until later in the evening due to work schedules and other obligations, this method may be hard to get used to.
However, other people instinctively eat this way already. They may be more prone to trying out an intermittent fasting eating pattern.
3. Works well with a nutritious, whole foods diet
Because intermittent fasting is focused more on when rather than what you eat, it’s generally easy to implement in conjunction with your current diet.
You won’t necessarily need to buy any special foods or diverge much from what you typically eat.
If you’re already content with the state of your current diet but looking for other ways to continue boosting your overall health, fasting might be something you want to explore.
For example, intermittent fasting might work particularly well for someone who wants to pair it with a resistance training program and a high protein diet (25Trusted Source).
Still, this isn’t meant to imply that what you eat doesn’t matter. There’s no doubt that you’ll reap the most benefits from intermittent fasting by eating a variety of nutritious foods and limiting ultra-processed foods during your eating window.
Intermittent fasting is often used to manage weight and metabolic health. The eating routine might help lower blood pressure, blood sugar, and blood fat levels. For some people, it also works as part of a healthy long-term diet pattern.
3 cons of intermittent fasting
Intermittent fasting is one way to regulate your calorie intake and work toward improving your metabolic health.
Though the eating pattern can certainly be part of a healthy diet, it will likely take some adjusting to in the beginning. Plus, simply put, intermittent fasting is not right for everyone.
Here are a few downsides you could encounter when first trying intermittent fasting.
1. Might go against your intuition
Intermittent fasting requires discipline, restraint, and planning ahead.
For some people, using those tactics to keep your calorie intake within a designated time frame is no problem, but for others, it might feel unnatural at first. This may be especially true if you’re used to relying on your intuition to decide when to eat.
Further, if you prefer not to follow a strict schedule, you might find intermittent fasting frustrating.
What’s more, if your schedule tends to vary from day to day because of work, family, or other obligations, keeping your calorie intake to a designated time frame could be challenging.
2. You’ll likely feel hungry
Even an 8- or 12-hour fast might feel like a long time when you’re not used to fasting.
You may go to bed hungry several times per week. That may naturally feel unpleasant and unsustainable in the long term (26Trusted Source).
Plus, at times, it might be necessary to override your natural hunger and fullness cues in order to not break your fast earlier than planned.
This doesn’t mean that fasting isn’t a schedule you can get used to. Once you’ve adjusted to intermittent fasting, you might even find it makes you feel less hungry (14Trusted Source, 15Trusted Source).
Many people adjust to the routine, and some even find they enjoy it after a few months. Yet, hunger and frustration are certainly something to expect and be aware of initially.
3. The side effects could affect your mood
When you first try intermittent fasting, one of the first things you may notice — aside from feeling more hungry — is ups and downs in your mood.
This is understandable. Besides initially increasing hunger levels, fasting can have side effects, including headaches, constipation, fatigue, sleep disturbances, and more (15Trusted Source, 27, 28Trusted Source, 29Trusted Source).
What’s more, irritability and anxiety are classic symptoms of low blood sugar levels. This is a common bodily response to fasting or restricting calories (30Trusted Source, 31Trusted Source, 32Trusted Source).
Still, like hunger, your emotional well-being may be another side effect of intermittent fasting that will improve with time and practice (15Trusted Source).
Once you’ve had time to adjust, intermittent fasting may even bring you a sense of achievement or pride (32Trusted Source).
Especially in the beginning, intermittent fasting can have side effects like hunger, headaches, and fatigue. The combination of low blood sugar levels from fasting and the stress of adjusting to a new routine could affect your mood and mental health, too.
The bottom line
Intermittent fasting is a weight loss tool that works for some people, but not everyone.
It’s not recommended for individuals who once had or currently have an eating disorder. It may also be unsuitable for children, people with underlying health conditions, and people who are pregnant or breastfeeding.
If you decide to try intermittent fasting, remember that just like with any eating pattern, diet quality is key.
To gain the most from intermittent fasting, be sure to eat a variety of nutrient-dense whole foods during your eating window and limit ultra-processed foods.
Furthermore, before embarking on an intermittent fast, be sure to consult a trained healthcare professional to ensure that it’s safe for you to do so.