Fasting is one of the oldest health traditions in the world and has been practiced throughout history for health, cultural, and religious reasons. As far back as Hippocrates, fasting was prescribed as a way of healing illness and improving cognitive abilities. Greek philosophers, those regarded as the fathers of modern medicine, and even Benjamin Franklin extolled the merits of fasting (5).
Fasting has recently gained a great deal of attention as research has found benefits to practices such as intermittent fasting. You may be looking for tips on intermittent fasting or you might want to learn more about different kinds of fasts.
When starting a fast, it’s important to understand the intermittent fasting rules. A fast is a window of during which little to no food is consumed, only water or non-caloric beverages. Some fasting days are marked with very low-calorie consumption, from 0- 500 calories (5, 6).
There is no single way to fast, and there are now several popular fasting methods. You can read more about the pros and cons of intermittent fasting here.
Popular methods include: (5, 6)
Fasting out of 7 days. Your fasting days must be non-consecutive. For example, if you fast on Monday, may fast again on Wednesday, Thursday, or Friday, but not Tuesday.
This pattern is similar to the 5:2, but there’s only 1 day of fasting rather than 2 days.
Only two large meals are consumed in a day, with the first between 6 and 10 am, and then lunch between 12 and 4 pm. There is no snacking and no third meal. Water and non-caloric beverages are allowed throughout the day.
This pattern involves only consuming food during an 8-hour window and fasting for 16 hours a day, every day of the week.
This involves fasting for 24 hours on alternate days. For example, you may fast on Monday, Wednesday, and Friday.
This approach aligns meal timing with your body’s natural rhythms. You can read more about circadian rhythm fasting here.
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Whether you’re fasting for weight loss or to improve other health outcomes such as blood sugar or gut health, there are certain intermittent fasting tips for success. One is to find a fasting pattern that works for you and that you can follow consistently.
You may notice that your body reacts to one fasting pattern, and you may experience unpleasant side effects such as low blood sugar or lethargy (5, 4). You may need to try another fasting pattern to see if something different works better for you.
Once you’ve found a fasting pattern that works well for you, try it for a few weeks in order to see the desired results (6). If you only follow a fasting pattern for 1-2 weeks, you may not see many improvements.
For those who are trying fasting to help with weight loss, intermittent fasting in a 16/8 or 5/2 pattern has been linked with successful outcomes (6).
Research supports fasting for short periods of up to 24 or 48 hours. Periods of fasting longer than 72 hours may increase incidences of irritability and mood changes, dehydration, hunger, fainting, and lack of energy and focus (9, 7).
Prolonged fasting periods have been linked to health concerns such as refeeding syndrome (8). If you’re new to fasting, you may want to start with a plan such as intermittent fasting for 16 hours per day.
If you’re new to fasting, you may want to start with intermittent fasting for 14-16 hours per day, and fast for just a few days a week. You can then gradually work to increase the number of days per week you fast or move on to longer fasting windows such as 16-24 hours, if desired.
During any fasting period, you must stay hydrated. On a typical day, you get approximately 30% of your fluid requirements from food, so dehydration is a distinct possibility when fasting (2).
Drink plenty of non-caloric fluids, especially water (1). You may also enjoy herbal teas, as they don’t contain caffeine. Moderate amounts of caffeinated coffee or tea are allowed, but skip the cream, milk, honey, and sugar.
Some exercise can boost energy levels when you’re fasting. They can also take your mind off fasting and allow you to focus on something else. Avoid heavy lifting or vigorous exercise during a fast.
Opt for slower walks, light yoga, or stretching to help your body feel its best and keep your energy levels up. If you’re having a hard time distracting yourself from your fast, you may want to listen to a podcast or audiobook while walking or stretching.
If you feel sick or experience symptoms such as weakness, fatigue, difficulty carrying out daily tasks, discomfort, or feeling sick, you may need to stop fasting (7).
When you’re allowed to eat again, it can be tempting to order that meal you’ve been dreaming about and drooling over, but it’s best to break your fast with healthy, whole foods that may be gentle on the digestive system.
Broth-based soups, plain yogurt, or smoothies are excellent options as they’re full of nutrients but not difficult to digest. Dates are often used to break religious fasts in Islam, as they are a nutrient-dense source of minerals, carbohydrates, and fiber (10).
As your feeding window goes on, include healthy foods such as whole grains, lean proteins, fruits, vegetables, and healthy fats. Try to eat normal, moderate meals during your eating window.
Read more: Intermittent Fasting and Running: A Winning Combination or a Terrible Mistake?
While it’s important to understand what to do while fasting, it’s also important to avoid common mistakes that could break your fast or increase your risk of illness, discomfort, or health complications when fasting.
If you’re fasting and start to have frequent headaches, lethargy, severe fatigue, or feelings of low blood sugar, don’t ignore these signs. You may need to try a different fasting pattern or eat lower-calorie foods on some days without completely restricting your caloric intake (4).
Remember that when you’re on a fast, drinking beverages such as milk, juice, lemonade, sweet tea, soda, and energy drinks will add to your overall caloric intake and can break your fast. While fasting, it’s best to stick to water, unsweetened teas, and coffees without cream, milk, sugar, or honey.
One of the most important tips for fasting for 24 hours or more is to avoid vigorous exercise or exercising for long periods. This can increase the risk of low blood sugar, low blood pressure, dizziness, or fainting.
If you’re fasting for only 14-16 hours a day, you may continue with your normal exercise routine, but you should go slowly to build up your stamina when you first start fasting. You may also consider scheduling your workout during your eating window or immediately after you start your fasting window, as you will have recently eaten.
If you’re fasting, you’re more likely to become dehydrated, so spending time in the hot sun or other hot environments such as a sauna, steam shower, or hot tub is ill-advised. You could experience low blood sugar, low blood pressure, lightheadedness, or fainting. (3)
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You can drink any non-caloric beverage you want while fasting. Make sure you drink plenty of pure water. You may also try caffeine-free teas to keep you hydrated. Some fasts allow for bone broth. You may consume moderate amounts of caffeinated coffee and tea without added sugar, milk, or cream.
For those who are trying fasting to help lose weight, the best intermittent fasting for weight loss may be a 16/8 or 5/2 pattern. Studies have found these patterns to be successful, and many people find them easy to continue with (6). Other tips for fasting to lose weight include finding a fasting pattern that you can be consistent with and making sure you don’t overeat during your eating windows, as this could compromise your results. If you’re wondering about the best macro ratio for weight loss while intermittent fasting, you can read more here.
A “dirty fast” is a fasting pattern that allows the consumption of low-calorie foods during the fast. This may be beneficial for those who want to try fasting but have certain health conditions or who have tried stricter fasting regimens and experienced difficulties. As some research has found fasting windows that allow for a few hundred to positive health impacts (5), many people are turning to “dirty fasting”.
Foods that are allowed on a dirty fast:
There are many ways you can incorporate fasting into your lifestyle. Intermittent fasting and dirty fasting are popular choices that are easy to follow, generally safe, and may help with weight loss and other health conditions. Many tips can make fasting easier and less uncomfortable, which increases your likelihood of continuing with fasting. If you have any concerns about safety while fasting or your health, talk with a doctor or healthcare provider.
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