Practical tips for fasting

We’ve dealt extensively with the science of fasting earlier, but sometimes there are many practical considerations that need exploring, too. Fasting, like anything else in life requires some practice.

In days past, when religious fasting was a communal practice, these sort of practical tips were passed on from generation to generation. If not, friends would often have useful advice on how to handle the fasting, because there are definitely some problems that commonly arise.

However, with the decline in the practice of fasting, these sorts of advice are often difficult to find. Unless you’re reading this.

What can I take on fasting days?

There are many different rules for fasting. During Ramadan, for example, fasting is practiced from sunrise to sundown and no food or beverages are taken. Other types of fasting will only restrict certain types of foods – for example, abstaining from meat for a day. So there are no right or wrong rules.

What I describe is the fasting that we prescribe for health and weight loss, as we use in our Intensive Dietary Management program.


All calorie-containing foods and beverages are withheld during fasting. Be sure to stay well hydrated throughout your fast. Water, both still and sparkling, is always a good choice.

Aim to drink around two liters of water daily. As a good practice, start every day with eight ounces of cool water to ensure adequate hydration as the day begins. Add a squeeze of lemon or lime to flavor the water, if you wish. Alternatively, you can add some slices of orange or cucumber to a pitcher of water for an infusion of flavor, and then enjoy the water throughout the day.

You can dilute apple-cider vinegar in water and then drink it, which may help with your blood sugars. However, artificial flavors or sweeteners are prohibited. Kool-Aid, Crystal Light, or Tang should not be added to the water.


All types of tea are excellent, including green, black, oolong and herbal. Teas can often be blended together for variety, and can be enjoyed hot or cold.

You can use spices such as cinnamon or nutmeg to add flavor to your tea. Adding a small amount of cream or milk is also acceptable (even if it’s technically a tiny cheat). Sugar, artificial sweeteners or flavors are not allowed.

Green tea could be an especially good choice, as the catechins in it are believed to help suppress appetite.


Coffee, caffeinated or decaffeinated, is also permitted. A small amount of cream or milk is acceptable, although these do contain some calories. Spices such as cinnamon may be added, but not sweeteners, sugar or artificial flavors. On hot days, iced coffee is a great choice. Coffee likely has many health benefits.

Bone broth

Homemade bone broth, made from beef, pork, chicken or fish bones, is a good choice for fasting days. Vegetable broth is a suitable alternative, although bone broth contains more nutrients. Adding a good pinch of sea salt to the broth will help you stay hydrated.

The other fluids — coffee, tea, and water — do not contain sodium, so during longer fasting periods, it is possible to become salt-depleted. Although many fear the added sodium, there is far greater danger in becoming salt depleted during fasting. For shorter fasts such as the 24- and 36-hour variety, extra sodium may not be required, but during longer fasts it can be important.

All vegetables, herbs or spices are great additions to broth, but ideally do not add bouillon cubes, which are full of artificial flavors and monosodium glutamate. Beware of canned broths: they are poor imitations of the homemade kinds.

Here’s a recipe for bone broth.

Break your fast gently

Be careful to break your fast gently. There is a natural tendency to eat large amounts of food as soon as the fast is over. Interestingly, most people don’t actually describe overwhelming hunger, but more of a psychological need to eat.

Overeating right after fasting may lead to stomach discomfort. While not serious, it can be quite uncomfortable. This problem tends to be self-correcting, i.e. most people will avoid it next time.

Try breaking your fast with a handful of nuts or a small salad to start. Then wait for 15-30 minutes. This will usually give time for any waves of hunger to pass, and allow you to gradually adjust. Short duration fasts (24 hours or less) generally require no special breaking of the fast, but certainly for longer fasts it is a good idea to plan ahead.

I get hungry when I fast. What can I do?

This is probably the number one concern. People assume they’ll be overwhelmed with hunger and unable to control themselves. The truth is that hunger does not persist, but instead comes in waves. If you’re experiencing hunger, it will pass.

Staying busy during a fast day is often helpful. Fasting during a busy day at work keeps your mind off eating.

As the body becomes accustomed to fasting, it starts to burn its stores of fat, and your hunger will be suppressed. Many people note that as they fast, appetite does not increase but rather starts to decrease. During longer fasts, many people notice that their hunger completely disappears by the second or third day.

There are also natural products that can help suppress hunger. Here are my top five natural appetite suppressants:

  1. Water: As mentioned before, start your day with a full glass of cold water. Staying hydrated helps prevent hunger. (Drinking a glass of water prior to a meal may also reduce hunger.) Sparkling mineral water may help for noisy stomachs and cramping.
  2. Green tea: Full of anti-oxidants and polyphenols, green tea is a great aid for dieters. The powerful anti-oxidants may help stimulate metabolism and weight loss.
  3. Cinnamon: Cinnamon has been shown to slow gastric emptying and may help suppress hunger. It may also help lower blood sugars and therefore useful in weight loss. Cinnamon may be added to all teas and coffees for a delicious change.
  4. Coffee: While many assume that caffeine suppresses hunger, studies show that this effect could be related to antioxidants. Both decaffeinated and regular coffee shows greater hunger suppression than caffeine in water. Given its likely health benefits, there is no reason to limit coffee intake. The caffeine in coffee may also raise your metabolism further, boosting fat burning.
  5. Chia Seeds: Chia seeds are high in soluble fiber and omega 3 fatty acids. These seeds absorb water and form a gel when soaked in liquid for thirty minutes, which may aid in appetite suppression. They can be eaten dry or made into a gel or pudding.


Can I exercise while fasting?

Absolutely. There is no reason to stop your exercise routine. All types of exercise, including resistance (weights) and cardio, are encouraged. There is a common misperception that eating is necessary to supply “energy” to the working body. That’s not true. The liver supplies energy via gluconeogenesis. During longer fasting periods, the muscles are also able to use fatty acids directly for energy.

As your adrenalin levels will be higher, fasting is an ideal time to exercise. The rise in growth hormone that comes with fasting may also promote muscle growth. These advantages have led many, especially those within the bodybuilding community, to take a greater interest in deliberately exercising in the fasted state. Diabetics on medication, however, must take special precautions because they may experience low blood sugars during exercise and fasting.


Do you want to know much more about intermittent fasting? Check out our full guide:

Intermittent fasting for beginners

Top videos about fasting

    The 2 big lies of type 2 diabetes
    The top 5 myths of fasting
  • The 7 benefits of fasting
    The cause of obesity

Earlier with Dr. Jason Fung

The Common Currency in Our Bodies Is Not Calories – Guess What It Is?

Why the First Law of Thermodynamics Is Utterly Irrelevant

How to Fix Your Broken Metabolism by Doing the Exact Opposite

More with Dr. Fung

Dr. Fung has his own blog at He is also active on Twitter.

His book The Obesity Code is available on Amazon.

The Obesity Code


  1. bahar
    I'm sure this article breaks all rules on fasting. Coffee? Cream? Bone broth? No way. Fasting is about healing. .. not cheating.
    Replies: #3, #4
  2. jc
    Tried to make it past 44 hours of fasting. Was never able. Read in OBESITY CODE (on pages 258-259; 262-265) how loss of salt was probably contributing to my "wilting" at the 44-hour mark.

    I prepared bone broth. Boiled beef bones; put it in the fridge until the fat had gelled at the surface; strained it; salted it; drank 2 cups per day.
    The salt made the difference. MAJOR difference. Thank you Doctor Bourne.

  3. John
    You seem to miss the point altogether.
  4. Dr. Andreas Eenfeldt, MD Team Diet Doctor
    Well, what if you can get 95% of the benefit, while enjoying the process instead of dreading it. Wouldn't that be a good trade-off?
  5. Heleen
    I fast on weekdays, sunday evening till saterday afthernoon and I feel great. I've three kids for whom I cook (LCHF) and that doenst bother me and yes I do take à coffee with cream ones in a while when the kids are eating their desert. You get justed to fasting, mentaly, fysicaly and emotionaly. I'm quite active and exercice a bit and that also doesn't pose à problem. Fasting has many benefits, but ease into it, start with every other day, or 12 h before you try longer. The only side effect I've is that I get cold easely.
  6. Tamarah
    I LOve Fasting,, I do it daily . I can plan my life so much better not worrying about food all the time. I drink tons of water ,, I have coffee with a little cream .I workout fasted daily . My weight is at a good place and doesn't move at all. I love this lifestyle and would recommend it to everyone .
  7. Kendle Laycock
    Does any kind of sweetener count or is it only artificial to avoid? What about stevia? I drink a mix of stevia, ACV, lemon juice, water/sparkling water and ice during the day sometimes.
    Reply: #37
  8. Raquel
    I can't seem to find information on this, so I apologise if it is in another post:

    Is it necessary to take supplements (e.g. a multivitamin; fish oil; etc.) when fasting?

    The benefits of taking vitamins seem dubious, and I usually don't take them, but I was wondering if while fasting they would actually be beneficial.

  9. Peter Biörck Team Diet Doctor
    Hi Raquel!

    If you are a member you can direct questions like that to our experts here:

    ( My opinion is that it should normally not be necessary. )

  10. Cathy
    Chia seeds during a fast? A tablespoon has 70 calories and 2 g protein. That won't interrupt the fast?
    Replies: #21, #23
  11. Ehsan
    Thanks for your nice passage
    I have a Question : is this fasting method cause plateau and not decreasing weight after a while?
  12. Marissa
    I was interested in how to fast in a healthy manner, but I think some people take it a bit far. No judgement, just my opinion. I generally only fast after a binge. This is to let my body attempt to rid itself of the unhealthy things I consume, which is why I am doing it now. I didn't know until after reading this article that a bit of creamer was all I was supposed to use in my coffee lol. I am grateful I found this article because it gives me a guide to fasting.
  13. Stacey
    Every day I do the 8:16 fast but I have a little whole cream in my coffee in the morning. Does this break my fast?
  14. Martin
    Try loooking @ Thomas delauer on youtube. He has some good videos about fasting. And much more strict than this one.
    I my self have followed his advice and im on day 6 with nothing but water, some salt and i lost 6.1 kg so far. Im 34 and now 101.4kg.

    Second. Thank you for a great site, with sooooo much help and usefull information to make this adaption of keto lifestyle easier.. Keep it up

  15. rohit
    I dont agree with sparkling water. Sparkling water contains CO2, which means you are adding carbon to your body. carbon adds weight to body. When we exhale we lose weight, though very tiny amount, but we do. Pls add pranayam and ayurveda to LCHF+IF to get even better results.
    Reply: #41
  16. Johann
    Dr. Gundry has raised concerns about lectins in chia.
    Reply: #45
  17. Jessie
    Does protein mess up fasting? I put collagen powder in my coffee every morning and it doesn't have a lot of calories but it is high in protein. I've seen several places where it suggests to keep calories under 30 to stay in a fasted state but nothing about protein consumption. I am new to IF so looking for more info. I'd like to keep adding collagen to my coffee if possible but don't want to defeat the purpose of the fast. Thanks!
  18. Lara Chan
    Where can we find answers to all these questions?
  19. Liljana Grncarovska
    I am on LCHF for two weeks and I feel great. Now I'm reading about fasting and have a question: In fasting period, is it allowed to put coconut oil in tea or coffee?
  20. sandy
    im on the 8:16 fasting plan.
    i would love to know, does eating anything i like or desire during the 8 hours help in weight loss?
  21. Vivian

    Chia seeds during a fast? A tablespoon has 70 calories and 2 g protein. That won't interrupt the fast?

    I also don’t understand how Chia seeds can be a part of fasting, and would appreciate some further information on that tip!

  22. Gregory
    I just did my first 24-hr fast and it was much easier this time around than previous times (when I wasn't on a keto diet). In fact, I'm going to try a 36-hour fast after a one day break. I just wanted to know why milk or cream is okay to be added to my tea, but a pinch of stevia is not recommended? Is it the possible sugar cravings? Thanks!
    Reply: #36
  23. Bianca
    I agree with you as well ! I would like more information on it
  24. Kerry
    As a vegan, can i drink miso broth whilst in fasting period?
    Reply: #25
  25. Kristin Parker Team Diet Doctor
    Yes, for most people that will not pose a problem.
  26. Alexa Eliopoulos
    I'm doing the 16/8 fast eating my 1st meal at 12pm last meal at BY 8pm. i'm confused about the eating window.. Once i'm able to eat am i allowed 2 meals during that 8 and window and have to stop by 8pm. Or should my next meal BE at 8:00pm? Both articles i read don't really say. please confirm. Can the 8 hour window period be 1-2 meals last being at 8pm or do i have my 1st meal at 12pm and then my last at 8pm?
    Reply: #27
  27. Kristin Parker Team Diet Doctor
    Ideally, all eating would be within the 8hr window, but there is some leeway if it's not exact.
  28. Dinah
    How long should I fast to prevent loose skin?
  29. ML Tenkula
    I’ve been diagnosed with PCOS and have been placed on all the usual meds. These meds require me to take them morning and evening not on an empty stomach. How will I be able to do a 24hrs fast or longer while still taking my medication? I hate getting nauseated. Please help the scale is not moving!!!!!
    Replies: #30, #42
  30. Kristin Parker Team Diet Doctor
    Taking your medication is far more important than fasting. You can eat keto/lchf without incorporating fasting and still see improved blood sugar and insulin levels and help improve the PCOS.
  31. Marja-Liisa Tenkula
    I understand it’s important to take my meds. But how do others on metaphormine fast?
  32. Anthony Koneh
    I am presently on the 24 hours fasting. My question is can I switch it up? that is three days dinner to dinner and another three days lunch to lunch. Is there any recommendation for sweetener for coffee.
    Reply: #34
  33. 1 comment removed
  34. Kristin Parker Team Diet Doctor

    I am presently on the 24 hours fasting. My question is can I switch it up? that is three days dinner to dinner and another three days lunch to lunch. Is there any recommendation for sweetener for coffee.

    Yes, that is fine to switch things up.

    Here is our guide on sweeteners -

  35. Philippa
    How do you take the salt? Just lick it or in water?
  36. Mike Stirewalt
    Check the ingredients in your stevia. The box of it I bought at Costco had several different things in it, including fructose.
  37. Julie
    Did you get an answer to this? My question too!
    Reply: #38
  38. Kristin Parker Team Diet Doctor

    Did you get an answer to this? My question too!

    You can see our sweetener guide here, which explains the pros and cons of different options.

  39. KJ
    Hello and thank you. What about flavored seltzer water like la croix? Is that ok whole fasting or not? Someone above balked at the CO2, but I don't know why that would impede the body from burning fat?
  40. Nguyễn duy minh
    16 years old get fasting
  41. Lonestar
    Drink it really fast and burp it out. Problem solved.
  42. Rachel
    I’m in the same boat! I take my morning meds with some coffee with a scoop of collagen (not sure if this technically breaks a fast, but it eliminates the nausea altogether). I take my evening pills with sparkling water and I seem to do ok 👌. Obviously I’m not an expert, but this is what works for me. Side note- if you are on Metformin and fasting BE CAREFUL! You can get pretty sick (definitely talk to your endo) best of luck
    Will taking powder collagen while fasting break my fast? Also I’m following dr. Fungus IDM to reverse diabetes many hours fasting will help me to reverse it ...I’m currently doing Monday, Tuesday, Wednesday starting on Sunday at 7: pm am I doing it right
    Reply: #44
  44. Kristin Parker Team Diet Doctor

    Will taking powder collagen while fasting break my fast? Also I’m following dr. Fungus IDM to reverse diabetes many hours fasting will help me to reverse it ...I’m currently doing Monday, Tuesday, Wednesday starting on Sunday at 7: pm am I doing it right

    Here is a good video where Dr Fung describes what breaks a fast.

    Here is our guide for reversing type 2 diabetes. What you eat is even more important than when you eat.

  45. Barrie Broadbent
    In my opinion, Gundry is a quack.
  46. 1 comment removed
  47. Mike
    Is it ok to have a protein shake on fasting days to protect lean muscle mass?
    Reply: #48
  48. Kristin Parker Team Diet Doctor

    Is it ok to have a protein shake on fasting days to protect lean muscle mass?

    A protein shake would likely break the fast. It might work better to prioritize protein when you are in your eating window.

Leave a reply

Reply to comment #0 by

Older posts