Let’s Talk About Types of Intermittent Fasting
Curious about this trending approach to eating? Learn more about the multiple ways to follow this plan and which one might be right for your lifestyle.
Intermittent fasting can be a powerful tool for weight loss and offer numerous health benefits, including a more efficient metabolism, sharper mind, and even a longer life. But it isn’t a one-size-fits all plan: There are several different ways to fast, which can make it tough to know where to start or which plan is best for you. If you’re curious about your options—and finding the plan that’s right for your lifestyle and health goals—keep reading.
Our Pro Panel
We went to some of the nation’s top experts in intermittent fasting to bring you the most up-to-date information available.
Vanessa Rissetto, R.D.
Registered dietitian and co-founder
Culina Health nutrition and health clinic
New York City
Christine Bishara, M.D.
Internal medicine doctor, certified in integrative medical weight loss
New York City
Steven Gundry, M.D.
Cardiothoracic surgeon; medical director
International Heart and Lung Institute Center for Restorative Medicine
Palm Springs, CA
While they all include some period of fasting with a predetermined eating window, when you eat and for how long can differ greatly depending on the type of plan you follow. Some (like the 16:8 plan) call for both eating and resting windows within a 24-hour period. Others, such as alternate-day fasting, require fasting every other day.
Many newcomers to intermittent fasting start with time-restricted eating (such as the 12:12 plan) because it doesn’t vary drastically from traditional mealtimes (morning, noon, and evening). This gives your body a chance to ease into fasting without leaving you famished, so you’re more likely to stick with the program.
Intermittent fasting doesn’t ask you to exclude specific foods from your diet. But experts caution against considering intermittent fasting as permission for all-out indulgence, especially if weight loss is your goal. Plus, healthy choices during your eating window will keep you full longer and give your body the nutrients it needs to sustain you until your fast is over.
Nope. Water, unsweetened tea, or coffee without milk won’t trigger your body’s digestive process, so they’re all okay to drink during your fast. Bottoms up!
What Is Intermittent Fasting, Anyway?
Before you can choose the intermittent fasting plan that’s right for you, it’s key to understand both what it is…and what it isn’t. Intermittent fasting isn’t a diet that requires cutting back on calories or banishing certain foods from your kitchen. Instead, it’s a way of organizing your food intake into eating windows and fasting periods so that your body has ample time to use what it has recently ingested for energy (namely, the carbohydrates in your last meal) and what it has in storage (fat).
What Are the Benefits of Intermittent Fasting?
Studies have shown some compelling health benefits of intermittent fasting that result from shifting the times you eat and allowing more time for digestion, including:
Weight loss. People who follow an intermittent fasting plan tend to consume fewer calories than average.
Improved brain function. When energy intake from food is reduced, wakefulness is increased because the nerve cell circuits are more active. According to recent research, fasting also promotes the production of new brain cells.
Reduced inflammation. Fasting, however, reduces the number of inflammatory cells in the bloodstream by limiting glucose intake, which, in turn, can help protect against chronic conditions, like heart disease.
Five Types of Intermittent Fasting
While not everyone experiences these benefits from intermittent fasting, enough positive experiences (especially those shared on social media) have convinced many people this eating approach is worth a try. If that’s you, these five types of intermittent fasting could be worth checking out.
Time-Restricted Intermittent Fasting
Time-restricted eating means compressing your meals and snacks into a window of several hours and then fasting for the remaining hours of the day. It is the most common approach to intermittent fasting and can be great for beginners because getting started can be as simple as cutting out late-night snacks and then delaying breakfast by a few hours. Easy enough, right?
Plus, water, unsweetened tea, and black coffee are permitted during the fasting window, which can help you feel less deprived. Another bonus: Time-restricted plans are easy to incorporate into daily life since much of the fasting window coincides with sleeping. Within this type of IF, there are several approaches:
16:8 Intermittent Fasting Schedule
Ever heard someone who fasts say that they don’t eat breakfast or insist on scheduling an early dinner? That’s because they’re probably on the 16:8 plan, the most common timetable. This plan requires you to fast for 16 hours (usually overnight and then some) followed by an 8-hour eating window, during which you aim to consume two or three meals.
14:10 Intermittent Fasting Schedule
Same as the above, but with a slightly shorter fasting period (14 hours) and longer eating window (10 hours).
12:12 Intermittent Fasting Schedule
This is where many first timers start, by eliminating evening snacks so that your body begins the fasting process right after you finish dinner. Then eat breakfast at your normal time.
To progress with this method of intermittent fasting, over the course of several days or weeks, delay your breakfast by an hour daily until you’ve stretched your fast to 14 or 16 hours. What’s so magical about 16 hours? That’s how long it takes to give your body a chance to finish burning off any recently consumed carbohydrates and then switch over to burning fat. It also allows the process of autophagy, or cellular detoxification and regeneration, to started. Autophagy is responsible for health benefits including reduced inflammation and possibly protection against age-related diseases, like Parkinson’s and Alzheimer’s.
Once you get into the groove, organizing your meals around your eating window becomes second nature.
Modified-Calorie Intermittent Fasting
Modified-calorie eating plans combine time restriction with reduced calorie intake on certain days. The goal: kicking your body’s fat-burning into overtime, as a lack of ready-to-burn fuel options such as carbohydrates forces it to dig deep into the reservoirs in fat cells, thus expending more energy and driving weight loss. The best-known modified calorie plan is the 5:2 method.
This version of the modified calorie plan calls for eating normally five days per week and reducing calorie intake to about 500 calories for women and 600 for men for the two remaining days per week. While you are not required to do the two fasting days consecutively, some experts believe it’s more effective because it gives your body a chance to be in a fasted state longer.
To try this type of intermittent fasting, stop eating after dinner the night before your first reduced-calorie (or fasting) day. During your reduced-calorie day, you can either eat one large meal consisting of 500 to 600 calories during the day or you can divide the calories into a few small snacks that add up over the course of the day. Repeat the pattern the next day or return to your normal eating routine and schedule a day later in the week with the same reduced calorie set-up.
Alternate-Day Intermittent Fasting
Alternate-day fasting (ADF) is a lot like the 5:2 plan, only it requires alternating between days of regular eating and days that allow for eating only up to 500 calories for women and 600 for men. The idea is to give your body a full day of rest after eating to allow the health benefits of fasting to kick in.
To practice alternate-day fasting, follow your normal eating routine for a day, keeping in mind healthy choices that include essential nutrition and will help keep you full, like fruits, veggies, protein, and whole grains. On your fasting days, choose to consume your calorie allowance in one meal at the time of your choice or in several smaller snacks.
OMAD (One Meal a Day) Intermittent Fasting
The OMAD (One Meal a Day) plan is pretty straight forward—and extreme. This type of fasting allows for consuming one meal a day (during a one-hour window) followed by a 23-hour fast. There are no food restrictions, and you can choose the hour you eat, so fasters are free to schedule their eating window whenever it works best for them. Also, water, unsweetened tea, and milk-free coffee are permitted during the fasting window so you can stay hydrated.
OMAD proponents like it because it’s simple to follow. And since it can be hard to regularly pack in a whole day’s calorie allowance into an hour-long eating window, OMAD followers tend to consume fewer calories overall. However, the plan comes with serious drawbacks, including limited food intake, depleted energy reserves, and a crash in blood sugar levels among some people. Critic also say it’s highly unsustainable for any duration of time, and the fallout from such severe dieting can be overeating once your willpower fail.
To try the OMAD plan, aim to consume close to the recommended calorie allowance for your gender, height, and weight during your single meal. It’s also key to include a variety of fruits and vegetables, whole grains, healthy fats (such as nuts, nut butters, and avocados), as well as lean proteins (such as chicken, fish, or tofu) to ensure you’re meeting your nutritional needs.
Since your goal when practicing OMAD is a 23-hour fast, you should aim to eat around the same time daily, however experts also recommend shifting your mealtime every so often, especially if it’s later in the day to allow your body more time to digest the meal before you head to bed.
Extended Intermittent Fasting
Extended fasts include any eating pattern that incorporates a fasting window longer than 24 hours. Some people use these to jumpstart a fasting routine or before a special occasion, but beware: Prolonged fasting could lead to dehydration and even cause the body to kick into survival mode, where it starts storing more fat in response to extended periods of deprivation.
Extended fasts should only be done under the supervision of a health care provider.
The main thing to keep in mind when choosing between the different types of fasting plans is sustainability. If the eating plan you have chosen is too hard to stick to even after an adjustment period, chances are you’ll abandon it. As with any healthy eating plan, consistency is key. Instead of focusing on a plan that has the most immediate results, focus on the one you can realistically stick to, given your lifestyle, so you can reap the benefits for the long haul.
Intermittent Fasting and Neurodegenerative Diseases: Experimental Biology and Medicine. (2018.) “Intermittent Fasting Protects Against the Deterioration of Cognitive Function, Energy Metabolism and Dyslipidemia in Alzheimer's Disease-induced Estrogen Deficient Rats.” https://journals.sagepub.com/doi/10.1177/1535370217751610
Intermittent Fasting Health Advantages: New England Journal of Medicine. (2019.) “Effects of Intermittent Fasting on Health, Aging, and Disease.” https://www.nejm.org/doi/full/10.1056/NEJMra1905136
Health Benefits of Autophagy: Autophagy. (2010.) “Short-term Fasting Induces Profound Neuronal Autophagy.” https://www.tandfonline.com/doi/full/10.4161/auto.6.6.12376
Intermittent Fasting and Metabolism: Annual Review of Nutrition. (2017.) “Metabolic Effects of Intermittent Fasting.” https://www.annualreviews.org/doi/full/10.1146/annurev-nutr-071816-064634?url_ver=Z39.88-2003
Brain Function and Alertness: Annals of Thoracic Medicine. (2018.) “The Effects of Diurnal Intermittent Fasting on the Wake-Promoting Neurotransmitter Orexin-A.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772108/
Inflammation: The American Journal of Clinical Nutrition. (2011.) “Low to Moderate Sugar-Sweetened Beverage Consumption Impairs Glucose and Lipid Metabolism and Promotes Inflammation in Healthy Young Men: A Randomized Controlled Trial.” https://pubmed.ncbi.nlm.nih.gov/21677052/
Diet and Inflammation (1): Cell. (2019.) “Dietary Intake Regulates the Circulating Inflammatory Monocyte Pool.” https://www.cell.com/cell/fulltext/S0092-8674(19)30850-5
Diet and Inflammation (2): The European Molecular Biology Organization. (2012.) “The Inflammation Theory of Disease.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3492709/