Intermittent fasting is a handy tool for those looking to lose weight and improve overall health. It’s become especially popular lately within the health world, highlighted by health gurus and big entrepreneurs like Tim Ferriss. While most types of intermittent fasting have great benefits, as discussed in our guide to fasting on keto for beginners, there are different ways of doing it.
If you’re not sure how to get started or wondering what fasting method might work best for you, this article can help. We’ll take a closer look at each type and the pros and cons of each.
#1 Fasting Within a Daily Window
This is often the most popular way of intermittent fasting, since it’s easier for us to naturally eat this way. For example, someone might skip breakfast and have their first meal at noon, then eat regularly throughout the rest of the day but stop eating at 8pm. This means you’d be eating for an 8-hour period and fasting for 16 hours.
These times are just an example, too. Some people might prefer to start eating later in the day (works especially well for those who are used to skipping breakfast), while others will start earlier and have an early dinner.
The amount of time for this varies. Some people will eat within a small timeframe, such as six-, four-, or even one-hour period, eating only one big meal per day. What’s important to remember here is that no matter when you do eat during the day, you should still get your day’s worth of calories and be mindful of macro and micronutrient needs.
Pros: Most people see the greatest success, and do so healthfully, with this method when sticking to a regular feeding time schedule and making it fit with your lifestyle.
Cons: Other than it possibly taking a little time to adjust to a fasting window that works for you, there aren’t many cons for this method. Just make sure you eat well and eat enough calories during the times you aren’t fasting.
#2 Alternate Days Fasting
This method involves fasting for a few days each week and eating as you normally would for the other days. For example, you could fast on Monday and Wednesday and eat normally the rest of the days out of your week.
Another version of this is the 5-2 method: eating normally five days out of the week and choosing two days to eat around ¼ of your regular caloric intake (which is usually around 500-600 calories for the average person).
Pros: Fasting on alternate days can be really flexible for most people and lets you customize your week. In a small study with 24 women, the 5-2 method was even found to help protect against breast cancer.
Cons: Simply restricting calories on the two days might be harder than just fasting for some people, plus there’s no guarantee it will put you into ketosis. The quality of the food definitely matters, so unless you focus on whole, low-carb foods, the low calorie days can be really uncomfortable.
#3 Skipping a Meal
It’s pretty self-explanatory: just skipping one meal out of your day. For example, you’d just eat two out of the “standard” three meals per day, skipping the usual time for breakfast, lunch, or dinner.
Pros: Simply skipping a meal works well if you’re new to fasting and want to keep it simple. Plus, it’s an easy way to save time and money if you’re traveling or stuck without food for a certain meal.
Cons: Sometimes skipping a meal without proper planning can cause one to overeat on the other meals, so it’s important to fill up on healthy fats and other keto foods to control hunger.
#4 Fat Fasting
Fat fasting is a common way of breaking a weight loss plateau, often for those who are already keto-adapted and in ketosis. Around 80-90% of calories come from fat, and calorie intake is usually kept low.
This can be combined with intermittent fasting, limiting your eating times to a smaller window, for even better results.
Pros: Just like with the ketogenic diet, the high amount of fat helps you stay satisfied and reduces hunger, making the fasting periods much easier than a diet more centric on carbohydrate foods. Plus, it helps guarantee you stay in nutritional ketosis and makes eating choices simpler.
Cons: Fat fasting can be rough, as you might quickly get tired of eating the same foods. Plus, due to the lower calorie intake, it’s not a good idea to do long-term. Fat fasting is meant to be done over a shorter period of time (no more than 3-5 days at a time) for quicker results, so it’s worth it if you can push through it during that time.
#5 The Warrior Diet
The Warrior Diet involves eating a small amount of fruits, vegetables, and and fast-assimilating protein like yogurt or whey protein every few hours and eating one very large meal within the last four hours of your night. If you’re focusing on keto foods, obviously you’d want to forgo the fruit and focus on low-carb vegetables and keto snacks.
Pros: Since small snacks are “allowed” before evening, it can be easier than forgoing food altogether during the day. Some people might also like eating a lot at night. Plus, the diet promotes high-quality foods choices and staying away from added sugars and processed foods.
Cons: The encouragement of a huge feast at night can cause some to overeat and lead to digestion problems from a ton of late-night eating.
#6 24-Hour Fasting
This one is fairly simple. Basically, you just fast from one meal (breakfast, lunch or dinner) to the same meal the next day. For example, you could stop eating after dinner one night and fast until dinner the next evening, or whichever meal works best for you.
It’s best to do this a couple days a week and eat normally the rest of the days.
Pros: This can be a good way to get into ketosis more quickly (taking exogenous ketones can help too) or give your body a good break from food.
Cons: Some people can find this method difficult and might do better beginning with a 12-16 hour fast first before building up their discipline.
#7 Only Eating When Hungry
While this might not be a structured way of “fasting,” it often naturally becomes a fast when you listen to your hunger. Basically, if you aren’t feeling hungry even though it’s “time” for breakfast, just skip it! Or forgo lunch or dinner if you’re not hungry during those times.
Pros: This allows you to listen to your body and also not overeat just because you feel like you must eat because it’s a certain time of day.
Cons: Just like with skipping a meal and the 5-2 method, this type of fasting doesn’t always guarantee ketosis if you aren’t eating keto-friendly — and even then, there’s no way to know for sure unless you’re testing your ketone levels. And as with every fasting method, eating well is a must for the best results.
Additional Fasting Guidelines
To get the most out of intermittent fasting, there are some good rules of thumb to keep in mind:
- No matter what method you use, the “rules” are pretty similar: During fasting times, plan to only drink water, black coffee, or other beverages without added sugars or calories, such as unsweetened iced or herbal teas. This will not only help you stay hydrated but also help reduce feelings of hunger.
- Even though fasting is great and healthy, it’s really important to eat high-quality foods during your feeding times, especially if weight loss and/or ketosis is your goal. See our list of ketogenic foods to help you stay in ketosis, and always remember to regularly test your ketone levels.
In addition, eating a low-carb ketogenic diet is a great addition to an intermittent fasting schedule since keto is known to blunt hunger.
Take Home Message
Intermittent fasting can be a great way to get into ketosis faster, boost weight loss, and reduce your chances of disease. No matter what method is used, intermittent fasting with healthy, whole foods eating periods can be a great way to increase the benefits of your ketogenic diet and ultimately take great care of your body.
Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.
After growing his sports rehab and functional medicine clinics to six locations in San Francisco, he shifted his mission to help as many people as possible achieve optimal health and well-being.