Question: “Does This Break My Fast?” Answer: “It Depends On What Type Of Fast You’re Doing”


by Nils Osmar. Dec. 14, 2022

I knew a woman once who was unusually serious about fasting. She had health problems she was hoping fasting might help with, but had developed a lot of anxiety about “doing it right”. The more “experts” she consulted, the more confusing it got. The question of whether a particular behavior (such as adding a sprinkle of salt to the water for electrolytes, or adding a little tea) was breaking her fast became a serious issue in her mind

The truth is that whether or not something breaks your fast depends on what type of fast you’re doing.

People get into fasting for a lot of reasons:

  • To lose weight (i.e., body fat).
  • To look better.
  • To take a break from foods they may be allergic or sensitive to.
  • To turn on autophagy and clean accumulated debris and clutter out of their cells.
  • To increase levels of NAD” (nicotinamide dinucleotide) (a compound that’s essential to life and DNA repair, which the body makes more of when we fast)
  • To experience ketosis and switch from burning glucose to burning fat.
  • To activate the sirtuin (longevity) genes.
  • To switch on AMPK (the longevity pathway) and take a break from the activation of mTOR (the growth pathway). (Anything that triggers the release of insulin tends to also activate mTOR.)
  • To kill off some sickly old (senescent) cells and get rid of defective mitochondria
  • To trigger stem cell regeneration and mitochondrial biogenesis. These occur, according to Dr. Valter Longo, in the week or so after a 3-5 day fast or fasting mimicking diet. (See article: “Fasting triggers stem cell regeneration of damaged, old immune system“)

Types of Fasts

When we’re fasting, we may feel hungry and be tempted to started adding little snacks in various forms, such as adding some cream to our tea and coffee and munching on carrots, celery sticks. We may also be tempted to add cream cheese and peanut butter to the celery, and add BCAAs to our coffee.

“Little things” like this can make the fast feel easier. But at what point have we defeated the purpose of the fast?

Let’s look at a few of the most common types of fasts, and the differing answers:

Dry Fasts

Dry fasts are fasts in which you don’t eat or drink anything for a prolonged period of time. Personally I don’t do dry fasts and don’t recommend them. But if for some reason you decide to do a dry fast, be aware that eating or drinking anything will break it.

Some dry fasting purists even claim that taking a bath or shower or washing your hands breaks a dry fast. People get a little carried away sometimes.

I don’t like or do dry fasts, and would not recommend doing one that lasts more than a few hours. We need water. Our early ancestors sometimes went for days without food when meat was scarce, but knew the importance of drinking water: “If you’re thirsty, find a stream and drink.”

Water Fasting

Water fasts are easy, right? Or at least they’re easy to describe. You just drink water.

But even on a water fast, most people add micronutrients sodium, potassium, or other electrolytes. For example, you might dash of sea salt to your water or a teaspoon or cream of tartar.

Technically these would be considered “breaking” the fast because it’s no longer water-only. But most health authorities would say that it’s absolutely necessary to do so, and that you’re risking serious health consequences if you don’t.

If you’re doing a water fast, then drinking anything but water (even coffee or tea) would technically break it. But if your goal is to promote autophagy (a kind of deep cellular cleaning) or lose weight, drinking coffee, green tea, white tea, or Earl grey tea would not be breaking it, because (1) they have zero calories, the same as water, and (2) they promote autophagy, and (3) they won’t take you out of ketosis.

Fasting-Mimicking Diets

An FMD lets you eat a very small amount of protein (from plant sources only), along with some carbs and fat every day. As the name implies, it’s not a real fast. It’s a (temporary) diet designed to mimic fasting. 

If you’re doing an FMD, water is allowed; coffee and tea are allowed; even green salads, some kinds of soup, and low-carb vegetable juices are allowed. But eating more than 15 grams of protein a day will break the FMD.

There are several kinds of FMDs. The kind I do is based around eating up to 400 calories per day, which includes 15 grams of protein (from plant sources); 30 grams of carbs; and around 50 grams of fat. Anything that exceeds these macros will break it.

It’s important to be aware that FMDs are starvation diets, intended to be followed for a few days at most. They are not “diets” a person could live on indefinitely.

Low-Carb Juice Fasts

Juice fasts (or “water-and-low-carb-juice” fasts) are ones in which we allow ourselves to drink water and juices of various kinds. They provide a few nutrients while still supporting weight loss, autophagy and ketosis. Some water fasts phase into being l0w-carb juice fasts as time goes on.

Drinks like water, celery juice, pickle juice and sauerkraut juice are all allowed on this type of fast.

I would never do, and would never recommend doing, a high carb juice fast. Sweet carbs (like fruit) trigger the production of insulin and take us out of ketosis and autophagy. Juices made from apples, oranges, grapes and other fruit (or berries) are not allowed on low-carb juice fasts.

Fat Fasting

Fat fasting is a curiosity that originally came from the Atkins diet. In it, you can eat lots of fat; you can pour cream into your coffee; but you don’t eat any other macronutrients. Some people swear by it but personally I wouldn’t recommend it.

“So can I drink coffee or tea when I’m fasting?”

  • No, if you’re doing a dry fast. (But again, I don’t personally recommend dry fasting)
  • No, if you’re doing a water-only fast. But the only reason I can see to do a water-only fast would be if you’re trying to avoid all possible food sensitivities or allergens.
  • Yes, if you’re doing a water plus coffee plus tea fast. (By definition, both coffee and tea are fine on this type of fast)
  • Yes, if you’re fasting for weight loss or autophagy. Coffee and green tea promote both. And they won’t interfere with ketosis. I’ll often drink coffee and tea, and sometimes also drink carbonated water, when doing a water fast.
  • Yes, if you’re doing a fasting mimicking diet.

One caveat: teabags can be a source of micro-plastics. A single teabag can release billions of plastic particle into a cup. See study: Plastic Teabags Release Billions of Microparticles and Nanoparticles into Tea. When I’m fasting, I drink coffee and tea, but use looseleaf tea, not bags.

What about Stevia?

  • According to this study, stevia does not actually increase insulin or glucose levels, so in that sense, it would not be viewed as breaking a fast.
  • According to this study, it actually increases insulin sensitivity, which is what we want,

“Can I add cream to my coffee or tea?”

  • If you’re fasting for autophagy or ketosis and don’t care about weight loss (or are trying not to lose weight), go ahead and add the cream (but no sugar).
  • If you are trying to lose weight, I would say, don’t add cream. The point is to start burning your own body fat, not burning the fat in the cream. And of course don’t add sugar.
  • With that said, Dr. Jason Fung has pointed out  that if adding a tiny amount of cream, such as a teaspoon or two, helps you to keep fasting, go ahead and add them. If it’s a question of breaking the fast and eating a big meal, or adding a tiny amount of cream, add the cream.
  • I’d agree with this advice. But don’t let a teaspoon or two turn into a tablespoon or two. Don’t add a whole pitcher.
  • If you’re doing time restricted eating, count the first cup of tea or coffee, or anything but water, as the start of your eating period. If you’re doing an 8 hour eating window, your last meal needs to end 8 hours after your first cup of coffee

Concluding Thoughts:

  • Pure water fasts are good for autophagy, ketosis, and taking a break from food allergens. They also give your digestive system a rest.
  • Drinking some tea or coffee, celery, parsley, cucumber or pickle juice, will not interfere with those processes. So I go ahead and drink them when fasting. (The metabolic effects of a low carb juice fast, or a fast that includes coffee or tea,  are pretty much identical to those of a pure water fast.) At that point I’m really from segueing from doing a water fast into doing a low-carb juice fast.
  • BCAAs activate mTOR and switch off AMPK. I completely avoid them when fasting.
  • Animal-based proteins include the amino acid leucine, which also activates mTOR and switches off AMPK. I’m not a vegan or vegetarian; I eat an omnivorous diet which does include some animal protein when I’m not fasting. But when I’m fasting, I go completely vegan for the duration of the fast.
  • You’ll find many opinions, some very different from mine, online. What I’m describing in this article is what works well for me.

Photo credit: Image by Vidmir Raic from Pixabay

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