Fasting and Caffeine with Tea

Caffeine's Impact on Fasting & Fasting from Caffeine: What You Need to Know

Posted by Stephany Morgan

Over the last few years, fasting has exploded in popularity as evidence mounts for intermittent fasting, and incorporating caffeine has become a core part of the discussion. Because tea is naturally calorie free and caffeinated, it of course tends to be front-and-center for people planning a new diet, fasting regime or “cleanse”. People are also starting to wonder about fasting from caffeine, to give their bodies a break.

...All of this meaning, I get a lot of questions about tea, caffeine and fasting! So today I will try to answer them.

Read on to learn:


  • Why do people fast? Are there different types of fasting?
  • Is caffeine bad for you? What does it do?
  • Full caf vs decaf vs caffeine-free tea: what should you know? What are the main decaffeination methods?
  • Should you do a caffeine fast? Should you quit caffeine entirely?
  • Can caffeine aid weight loss?
  • Caffeine supplements vs caffeine in tea and coffee: What’s safe?
  • Can you drink tea on a fast? Can you drink caffeine while fasting?


Why do people fast? Are there different types of fasting?

In its simplest definition, fasting simply means going without food and drink for a period of time. The most well-known reason for fasting is religious reasons, followed by fasting for medical reasons (an upcoming surgery, blood test, exam, etc). But increasingly, research is showing that fasting for health reasons has some merit.

Whether fasting is for you or not is a topic in and of itself - that’s a topic for another forum and day! Today I’m only discussing the impacts of caffeine and tea on fasting for health or dietary reasons, as otherwise this piece will become a novella and nobody wants that.

So, why do people fast? Well, it all depends on your goal: Some people will fast from only solid foods for example, or from foods that lead to glucose and/or insulin responses. Some people will avoid all food, but will drink water or calorie-free liquids to achieve “autophagy” (a process where the body removes and recycles malfunctioning cells - see my last section about Fasting Teas below for more on autophagy).

Meanwhile, other fasters aim to reduce insulin responses solely so they will allow high fat, high calorie foods and drinks that don’t evoke insulin responses (this is part of the Keto diet).

And then of course, today’s topic: fasting to “detox” the body of a certain substance, such as caffeine. This involves avoiding a certain ingredient, but otherwise eating and drinking as normal.

Basically, what breaks a fast depends on your intention and goal with the fast. Many intermittent fasters have different goals, so the answers will differ for them. That’s why it’s so important to understand the science of what happens when you drink caffeine, so you can decide if it fits with your fasting regime.


Tea with rock sugar

Fasting as part of the Keto diet aims to reduce insulin responses, caused for example by eating tasty rock sugar 


Is Caffeine Bad For You?

When it comes to caffeine there are many health implications. Whether it is “good” or “bad” depends on a variety of factors such as the individual, the form it is being consumed in, as well as frequency and dose. Practitioners have a saying: “The Dose Makes the Poison”. Caffeine is a substance that should be treated as medicinal, and therefore dose should be adhered to.

For example of how important dosage is, between 200-250mg of caffeine has been linked to an elevated mood, and 600mg has been associated with anxiety and tension.

While studies have found health benefits, there are concerns as well. Caffeine can provide energy, appetite suppression, elevated mood, improved focus and alertness, and even decrease suicide risk (Medline, Schubert, Penetar, Penetar, and Lucas).

However, it can also cause pregnancy complications, withdrawals, headaches, elevated blood pressure, elevated cortisol (stress hormone) and adrenal fatigue (increased excretion of adrenaline), and in severe cases of overdose, even death (APA, Mayo Clinic, Lopez-Jimenez, Lovallo, Ryu, and Cappelletti).

In the Lovallo study, it showed cortisol initially elevates but then decreases with consistent consumption. Adrenal fatigue occurs when stress hormones are consistently over-produced until the adrenals experience exhaustion and then they stop producing adequate, balanced amounts (which is not good as there are times where cortisol production is necessary).


Green tea and teapot

Read about the impact of caffeine on kidney health in

Is Tea, Coffee or Caffeine Good for Your Kidneys?



Caffeinated Teas, Decaffeinated Teas, and Caffeine-free teas: Which is Best?

Keeping dose in mind, caffeinated teas by nature are not inherently bad. We all know that some countries consume a lot of green tea, which naturally contains caffeine. People in Asian countries are considered very healthy and part of that is due to tea consumption which averages about 1.2 liters per day (Yale)!

Decaffeinated green tea exists, but removing the caffeine is a chemical process which could overarchingly outweigh the benefits of consuming a whole, untampered herb.

On the plus side, the carcinogenic benzenes once used in the decaffeination process have been replaced with solvents now considered safe (Chamberlain). If trying to avoid chemical solvent methods, opt for organic decaffeinated options (which use heat, water, and pressure to decaffeinate the plant material, i.e. the CO2 method).

That, and even decaffeinated beverages still contain some caffeine and are not recommended for highly sensitive individuals (Chamberlain). This, of course, depends on the individual as caffeine allergies do exist.



Sea Air Decaf Sencha Green Tea

If you're looking for an extremely rare decaf, try our 

Sea Air Decaf Sencha Green Tea


What are the main ways to decaffeinate tea?

These are the three primary ways to remove caffeine from tea leaves. Please note that it is NOT possible to decaffeinate tea at home, despite what the internet says! To remove enough caffeine for your leaves to actually be decaf, you would have to steep your leaves for ages - removing all the taste and oils before the caffeine. So don't bother!

  1.  The methylene chloride method: This practice involves submerging the tea leaves in methylene chloride. The caffeine molecules bind with the solvent, and voila the leaves are decaffeinated. The flavors and oils are then added back in. Interestingly, 99% of the decaf tea sold in the UK is treated using this method! It’s the least preferred method, though, as methylene chloride is highly toxic so you have to be confident that it has all been removed (Gerst).
  2.  The ethyl acetate method: This is another solvent (found in fruit, and nail polish remover), and can leave a “chemical” taste. Quite common for bagged and mass produced teas, and uses the same method as methylene chloride decaffeination. Considered to be preferable to methylene chloride, simply because the solvent is less toxic (Gerst).
  3.  The carbon dioxide / CO2 method: By far the preferred method, in that it doesn’t expose the tea leaves to chemical solvents (the caffeine molecules instead bind to the CO2 molecules which are then removed). It also leaves the flavor the least changed of these various methods (More than Tea). However, it is by far the most expensive and so generally used for higher quality / loose leaf teas (Gerst). Because life is too short to drink bad tea, right?

If you are determined to avoid caffeine, there are also plenty of herbal options to choose from which naturally do not contain caffeine, such as rooibos, honeybush and chamomile. Some are even energizing, like Moringa and Ginseng (Arring).


Moringa: The Complete Vegan Protein
Never heard of Moringa? Learn all about it here:



Should I Fast From Caffeine for a Detox?

Caffeine has something called a “half life”, which is the amount of time it takes for your body to metabolize and excrete it. For example, caffeine’s half life is 5 hours, which means it takes five hours for the body to reduce 120 milligrams of caffeine down to 60 mg (Olsen). So your morning cup of joe at 7 am will still have you operating on 60 mg of caffeine at noon. After another five hours the body will have 30 mg of caffeine remaining.

If you are used to caffeine you don’t have to detox so much as wean off of it due to chemical dependency. This can be done in various ways, but doing so gradually can help avoid some uncomfortable withdrawal symptoms (Sajadi-Ernazarova).

Basically, caffeine is out of your system in the time it takes to break down, so if you don't have any for the period of that half life you are technically "detoxed" from it. Then it's simply a matter of how dependent you are on it.

This is where the weaning helps, but it doesn't really have anything to do with detoxification because the chemical is no longer in your system. I have searched and searched, but can’t find any research to support a need for caffeine detoxification, only for allowing the caffeine to work its way out of your system within its half-life period.

All that being said, once caffeine leaves your system, abstaining from this stimulant can give your brain and eliminatory organs a reprieve.


Coffee Lattes

The main reason for caffeine 'fasting' is actually caffeine 'weaning', to reduce or end the body's dependence on this stimulant


Can Caffeine Aid Weight Loss?

The Mayo Clinic claims that while it may supplement weight loss, it has no significant impacts on weight loss by itself (Zeratsky). Updated in 2020, the article states that weight loss studies on caffeine were poorly done, or only done in animals and so the evidence is not high quality (Zeratsky). Even decaffeinated coffee supported weight loss in participants, suggesting that there is more than caffeine at play.

A review of the literature examined 13 randomized controlled trials with 606 participants and concluded that caffeine may promote weight loss and fat reduction (Tabrizi). Caffeine is a stimulant, which can increase metabolism and thermogenesis.

A rat study found that caffeine increased the calorie expenditure of exercise (meaning you burn more calories on caffeine than you do without), which is probably why so many weight loss and workout supplements contain it (Clark).

While these effects sound promising, remember that the body quickly adjusts to stimulants so they begin to lose these benefits over time. It has also been observed that caffeine is more effective in lean consumers (Bracco).

My final verdict is that because caffeine may increase thermogenesis and caloric expenditure, it may make exercise more effective. In terms of weight loss, however, the type of exercise will impact whether you are burning calories and glycogen or actual fat (the first will help maintain weight, and prevent additional gains, but the second will alter body composition.

Fat can be burned via cardio so long as there is a caloric deficit. In that case, supplementing with caffeine is a personal choice) (Booth).

The more studies I peruse, the more I believe that caffeine supplements weight loss via synergistic action, but is not highly effective alone.


Tea vs Coffee

Does it matter if you drink tea or coffee, in terms of weight loss?


Do weight loss outcomes vary from caffeine in tea vs coffee?

The only conclusions regarding caffeine and tea and coffee is that caffeine may support the weight loss effects of the beverage, but is less effective alone, and those who consumed even decaffeinated coffee still lost weight, suggesting the weight loss effects are not actually due to the caffeine.

In my research I didn't come across anything that looked at the differences between tea and coffee, but I do not think such differences are measurable. They'd have to isolate the caffeine from the plant - and then you simply have caffeine.

So, it is more likely a combination of how caffeine interacts with the profiles of the plants that contain the caffeine. It could also have to do with the stimulant action of other caffeine like compounds (xanthines). I looked into this, and other than ephedrine (which is no longer legal), there don't appear to be weight loss studies on other xanthine compounds (which behave like caffeine and are often in these teas/coffees in varying ratios).


Anhydrous Caffeine (and Weight Loss Supplements)

Anhydrous means without water. This form of caffeine is extracted directly from the seeds and leaves of caffeine-containing plants (usually the coffee plant- Coffea arabica) (Wilson).

This creates a powdered caffeine concentrate, which can easily lead to health concerns via overdose. The FDA issued warning letters to manufacturers, stating that exact dosing proportions are impossible to quantify with common kitchen measuring devices (FDA). In fact, just a teaspoon can equate to 28 cups of coffee, and deaths have occurred as a result of consuming anhydrous caffeine.

Adults can safely consume up to 400 mg of caffeine in their beverages daily (Mayo Clinic).

But be aware, if you are drinking your caffeinated tea or coffee and then opt to take a weight loss supplement, you can quickly exceed this safe dose limit if anhydrous caffeine is included in the supplement.


Herbal tea with rose petals

Many herbal teas have some natural sweetness that helps if you have a sweet tooth, but don't want to add honey or sugar


What About Fasting Teas? Intermittent Fasting and Tea

Can I have tea on a fast? Will drinking tea break my fast? These popular questions permeate the intermittent fasting world. Many people are asking about fasting tea and coffee and wondering what they can do to stay in ketosis (if doing keto, too) and lose weight. One resounding question centers around the beloved morning caffeine ritual many of us have. But don’t fret! You can have your coffee and drink it, too (Zambon). Same goes for tea!

To not break a fast, it needs to be plain. If you enjoy honey in your tea, you’ll have to wait for a non-fasting period for that golden goodness, because honey in tea during a fast is a no-no.

But don’t worry! There are a lot of calorie-free sweet substitutes that can easily replace honey and keep you fasted, Golden monk fruit sweetener (a zero calorie, sweet tasting amino acid) and stevia are two options that are also free from sugar alcohols. Erythritol and allulose are zero-calorie sugar alcohols that are approved for fasting as well.


Does matcha tea break a fast? How about Moringa Powder?

A good question, given when you consume matcha or Moringa Tea Powder you are consuming the leaf itself, which of course contains some calories.

If the main goal of the fast is autophagy, then as a general rule one should not consume more than 30 calories. Given one serving of moringa (about a tsp) is well under 30 calories (only around 3.5 calories), it will not break the fast. Likewise, 1 tsp of matcha is around 5 calories, so also well within the limits!


For the tea nerds out there, here’s some TEA MATH:

Matcha calories (from Kineta):

  • 100 grams of matcha = 324 calories, about 1 ¼ cup
  • 1 ¼ cup = 20 tablespoons = 16.2 calories per Tbsp.
  • Given there are 3 teaspoons in each tablespoon, 1 tsp matcha = 5.5 calories


Pure matcha in chawan

Moringa calories (from Gopalakrishnan et al):

  • 100 grams of moringa leaf powder = 205 calories, about 1 ¼ cup
  • 1 ¼ cup = 20 tablespoons = 10.25 calories per Tbsp.
  • Given there are 3 teaspoons in each tablespoon, 1 tsp moringa = 3.5 calories


When can I have calories during a fast? What can I drink to suppress appetite? 

And now that I’ve said that you need to avoid calories while fasting, I’m going to add an exception: if you are trying to get into or stay in ketosis, you can have a "keto coffee" or “keto tea” worry free: this is a high fat beverage with plenty of calories which "doesn't break the fast" because fats do not evoke insulin responses (Bates).

Actually, the appetite-suppressing action of caffeine in coffee and caffeinated teas can help intermittent fasting by making it easier to resist hunger (Schubert).

Furthermore, the antioxidants in tea (such as EGCG) can promote a natural detoxification process called autophagy (which kicks in during fasting) (Holczer).

 Green Tea Leaves
For a refresher on what EGCG and catechins are, read



During a fasted state, EGCG promotes cell health and autophagy-related cell survival and also activates AMPK- an enzyme which increases the release and use of fatty deposits (Holczer, Li). EGCG from green tea can also mimic calorie restriction, making it a great option as a fasting tea!



Stephany Morgan

Note from the Herbalist...

I hope all this was useful, and can help you make healthy, informed decisions about your fasting. If you have any questions, please share in the comments section below!

About the Author:

Stephany Morgan (MSc Complementary and Alternative Medicine) is a herbalist, professor, and healthcare professional. After earning her BS in Psychology and Pre-Nursing from Rochester College with a minor in General Science she began her formal pursuit of natural medicine.

Stephany went on to earn her MSc in Complementary Alternative Medicine at the American College for Healthcare Sciences (ACHS), where she focused her studies on Herbal Medicine and Nutrition. Most recently, she completed her Graduate Certification in Nutrition from ACHS in 2020. She is currently a professor at White Earth Tribal and Community College (WETCC) in Minnesota as part of a pilot project with Lead for America. 


Sea Air Decaf Sencha Green Tea

Sea Air Decaf Sencha Green Tea

 A very rare tea: a decaf Japanese tea. One sniff and you're at the seaside, smelling the fresh sea air, with no caffeine in sight

$7.50 with Free US Shipping 

Vanilla Almond Wonderland Rooibos

Vanilla Almond Wonderland Rooibos

 Naturally caffeine free, round and delicious. Calorie free too, so perfect for any type of dietary fast!

$6.00 with Free US Shipping 


Learn more about caffeine:

Caffeine in Coffee and Tea: All You Need to Know


Read about keto and paleo teas:

Best Teas for the Keto and Paleo Diets


Explore our Tea Science & Lifestyle blog | Subscribe to the MA Blog to save 15%!



with FREE US shipping!

All of the information regarding the herbs, botanicals, minerals, vitamins, etc., is information drawn from traditional use data or academic research and should be regarded as such. If you, the reader, has a health or medical concern, please consult your healthcare professional. The information found here is not meant to diagnose, treat, prescribe or cure and has not been evaluated by the FDA. This information is for educational purposes only. 


Read more about tea, caffeine and diet:

➔  Caffeine in Coffee and Tea: All You Need to Know

➔  Mythbusting Tea for Weight Loss in 2021: Which Teas Help with Fat Metabolism?

➔ Is Cold Brew Tea Better for You? Antioxidants in Iced Tea vs Hot Brew 


References & Further Reading for Tea & Fasting

MedlinePlus. Caffeine.

Schubert MM, Irwin C, Seay RF, Clarke HE, Allegro D, Desbrow B. Caffeine, coffee, and appetite control: a review. Int J Food Sci Nutr. 2017 Dec;68(8):901-912. doi: 10.1080/09637486.2017.1320537. Epub 2017 Apr 27. PMID: 28446037.

Penetar, D, et al. Institute of Medicine (US) Committee on Military Nutrition Research; Marriott BM, editor. Food Components to Enhance Performance: An Evaluation of Potential Performance-Enhancing Food Components for Operational Rations. Washington (DC): National Academies Press (US); 1994. 20, Effects of Caffeine on Cognitive Performance, Mood, and Alertness in Sleep-Deprived Humans. Available from:

Lucas, M., O’Reilly, E. J., Pan, A., Mirzaei, F., Willett, W. C., Okereke, O. I., & Ascherio, A. (2013). Coffee, caffeine, and risk of completed suicide: Results from three prospective cohorts of American adults. The World Journal of Biological Psychiatry, 15(5), 377–386.

APA. Caffeine During Pregnancy.

Mayo Clinic. Nutrition and healthy eating. 2020.

Lopez-Jimenez, F. 2021. Caffeine: How does it affect blood pressure? The Mayo Clinic.

Lovallo, W. R., Whitsett, T. L., al'Absi, M., Sung, B. H., Vincent, A. S., & Wilson, M. F. (2005). Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosomatic medicine, 67(5), 734–739.

Ryu, K. Y., & Roh, J. (2019). The Effects of High Peripubertal Caffeine Exposure on the Adrenal Gland in Immature Male and Female Rats. Nutrients, 11(5), 951.

Cappelletti, S., Piacentino, D., Fineschi, V., Frati, P., Cipolloni, L., & Aromatario, M. (2018). Caffeine-Related Deaths: Manner of Deaths and Categories at Risk. Nutrients, 10(5), 611.

 Yale University. "Green Tea And The 'Asian Paradox'." ScienceDaily. ScienceDaily, 6 June 2006. <>.

Chamberlain, C. 2020. Is decaf tea and coffee bad for you?

Gerst, Paul. 2020. Your Complete Guide to How Decaffeinated Tea is Produced

It’s More Than Tea. 2019. How Tea Is Decaffeinated. It's More Than Tea, Jill's Tea Blog.

Arring, N. M., Millstine, D., Marks, L. A., & Nail, L. M. (2018). Ginseng as a Treatment for Fatigue: A Systematic Review. Journal of alternative and complementary medicine (New York, N.Y.), 24(7), 624–633.

Olsen, N. 2018. How long does a cup of coffee keep you awake?

Sajadi-Ernazarova KR, Anderson J, Dhakal A, et al. Caffeine Withdrawal. [Updated 2021 Jun 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:

Zeratsky, K. 2020. Does caffeine help with weight loss? The Mayo Clinic.

Tabrizi, R., Saneei, P., Lankarani, K. B., Akbari, M., Kolahdooz, F., Esmaillzadeh, A., Nadi-Ravandi, S., Mazoochi, M., & Asemi, Z. (2019). The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials. Critical reviews in food science and nutrition, 59(16), 2688–2696.

Clark, K. S., Coleman, C., Shelton, R., Heemstra, L. A., & Novak, C. M. (2019). Caffeine enhances activity thermogenesis and energy expenditure in rats. Clinical and experimental pharmacology & physiology, 46(5), 475–482.

Bracco, D., Ferrarra, J. M., Arnaud, M. J., Jéquier, E., & Schutz, Y. (1995). Effects of caffeine on energy metabolism, heart rate, and methylxanthine metabolism in lean and obese women. The American journal of physiology, 269(4 Pt 1), E671–E678.

Booth, L. How Does Cardio Burn Fat (Research From 5 Studies). Fitbod.

Wilson, D. 2018. What’s the Difference Between Caffeine and Caffeine Powder?



FDA. 2018. Pure and Highly Concentrated Caffeine.

Zambon, V. 2021. What you can and cannot eat and drink while fasting.

Kineta. Matcha Tea Nutrition Facts. 

Lakshmipriya Gopalakrishnan, Kruthi Doriya, Devarai Santhosh Kumar, Moringa oleifera: A review on nutritive importance and its medicinal application, Food Science and Human Wellness, Volume 5, Issue 2, 2016, Pages 49-56, ISSN 2213-4530, (

Li, F., Gao, C., Yan, P., Zhang, M., Wang, Y., Hu, Y., Wu, X., Wang, X., & Sheng, J. (2018). EGCG Reduces Obesity and White Adipose Tissue Gain Partly Through AMPK Activation in Mice. Frontiers in Pharmacology, 9.

Bates, Autumn. Autumn Elle Nutrition.

Holczer, M., Besze, B., Zámbó, V., Csala, M., Bánhegyi, G., & Kapuy, O. (2018). Epigallocatechin-3-Gallate (EGCG) Promotes Autophagy-Dependent Survival via Influencing the Balance of mTOR-AMPK Pathways upon Endoplasmic Reticulum Stress. Oxidative medicine and cellular longevity, 2018, 6721530.


Older Post Newer Post


Leave a comment

Please note, comments must be approved before they are published