Dry fasting — the complete guide

Written by Trey Reck

Medically reviewed by Josie Porter, RD

Published on December 23, 2022 | Updated on June 10, 2024

When you hear the words “dry fasting,” what do you think of? 

Do you wonder if this is a fasting schedule where alcohol is prohibited for 16 hours, and then it’s whiskey, gin, and vodka for the next eight?

Maybe an image of you on a sandy desert, sweating while you fast under the beating sun pops into your head.

Or you contemplate the kinds of foods you might be “allowed” to eat on a dry fast: cornflakes without milk, crackers, stale bread, sauceless chicken. 

A dry fast is none of these things. 

Dry fasting means you restrict food AND liquid during your fasting periods. Yep, that’s right — no water, no tea, no black coffee, and no food. 

We’d never recommend dry fasting to you (or an alcohol fast, a desert fast, or a cracker fast) as a way to improve your health. At Simple, we also don’t recommend any fast that involves not eating or only eating / drinking a limited amount) for 18+ hours. These fasting schedules involve more potential risks and safety concerns, and there isn’t really evidence to suggest they’re more effective results-wise.But we do want to help you learn more about dry fasting so you have all the information about what it is and why other people might recommend it so you can decide whether you want to try it or not.

What is dry fasting?

Like ironing, fasting also comes in extreme forms. Dry fasting is one of those extremes because, when you do it, you fast from everything.

Any of the intermittent fasting methods can be done dry. (Except water fasting, obviously.) 

No matter what fasting schedule you follow, if you remove all liquid from your fasting period, you’re dry fasting.

During your eating window, you can eat and drink as you wish.  

It’s pretty straightforward, if extremely restrictive.

But whether it’s safe or effective is questionable. We’ll look at dry fasting’s benefits, risks, and results later. 

How does dry fasting work?

There are no set dry fasting rules, stages, or guidelines. 

Here’s the essence: 

• restrict liquids and food during your fasting window
• eat and drink as you typically would during your eating window

It’s no more complex than that.   

One popular argument for how dry fasting works is that when you go without food or water for a period of time, your body increases fat metabolism to access the water in your fat cells, and you lose weight. 

But there’s a lot more evidence that drinking water assists weight loss. For instance, a systematic review showed that increasing total water intake and drinking water before meals can support weight loss,[1] while another systematic review showed that increased water consumption while following a weight-loss program reduced body weight after 3 to12 months — compared to following the weight-loss program alone.[2]This is one reason why a plentiful water intake helps you succeed at reaching your weight loss goals through intermittent fasting (and why not drinking enough is one of our top intermittent fasting mistakes).

The best way to prepare for dry fasting

There are a few steps you can take to prepare yourself for dry fasting. 

1. Talk to your healthcare provider. 

We always recommend talking to your healthcare team before trying any fasting approach, but it’s especially important if you’re considering dry fasting (or any more extreme fasting method, like fasts that last 18+ hours). They will have some insights on how this type of fasting might interact with your health and can guide you on whether it’s safe — not to mention worthwhile — for you to try. 

2. Get comfy with intermittent fasting. 

Ease into the fasting experience by following a less restrictive intermittent fasting schedule for a few days or weeks. Practice drinking enough and eating plenty of fruit and veggies during your eating window to help you get used to:

• eating fewer calories
• the act of fasting itself
• getting enough hydration in a shorter period of time

If this is where you’re at, we can help. Time-restricted eating approaches like 12-hour intermittent fasting, 14:10 intermittent fasting, and 16:8 intermittent fasting are our most recommended fasting schedules since they’re easier on your body and still serve up all the potential fasting benefits you may be after. Head to our Simple quiz, and we’ll recommend the one that might work best for you. 

3. Make sure you’re hydrated in the days leading up to starting your dry fast. 

Before you start dry fasting, focus on being fully hydrated by:

• drinking plenty of water 
• cutting out caffeine and alcohol

This will make sure you’re in a good place to kick off your dry fast. 

How long can and should you dry fast?

Studies on dry fasting tend to focus on Ramadan, where the fast periods — i.e., the unbroken length of time someone goes without food or water — can be between 10–19 hours, and intermittent dry fasting is done for 30 days. We don’t have any real evidence that it’s safe to dry fast if you’re doing it at home (especially for longer than that) without the care and supervision of a medical professional.

The best way to break your dry fast

When you come to break your fast, start out with a glass of room-temperature water, then eat something that’s easily digestible and nourishing. Try eating light foods that release energy steadily, like:

• a veggie bean salad
• chicken broth 
• a smoothie with berries and live yogurt 

Important note: If at any point during your fast, you feel:

• dizzy
• light-headed
• spaced out
• exhausted
• sick 

… break your fast. 

These are your body’s ways of telling you to eat and drink. Stay checked in, pay attention to how you feel, and follow your body’s signals. Also, keep in mind that with more extreme fasting approaches like dry fasting, your risk of experiencing these side effects is higher, so you want to be hyper-aware of how you’re feeling.

Dry fasting and weight loss

Intermittent fasting is a reliable method of weight loss, but whether dry fasting brings any benefits to the party, above and beyond those of regular intermittent fasting, is unclear.

A 2013 study found that 240 healthy adults who intermittently dry fasted for at least 20 days during the month of Ramadan decreased their body weight and BMI.[3]

A scientific review suggests dry fasting during Ramadan has similar benefits on weight loss as time-restricted fasting (like 16:8).[4] 

However, dry fasting during Ramadan is short term (it takes place over 30 consecutive days), and its results are too, meaning the weight loss you achieve likely won’t be sustained once you stop dry fasting. 

Currently, there isn’t enough evidence to demonstrate how effective dry fasting is for weight loss over the long term — and not really any to suggest it’s more effective than other less restrictive fasting approaches. 

Health benefits of dry fasting

There are some potential benefits of dry fasting. 

However, bear in mind that these benefits are also found in studies of other intermittent fasting methods, and there are no studies that compare regular intermittent fasting methods with dry fasting. 

Just as with weight loss, we can’t know whether dry fasting offers any benefits beyond those of intermittent fasting in general. 

Fat loss

In a 2016 study, those who dry fasted during Ramadan lost weight and lost body fat while keeping their muscle mass.[5] 

Better blood sugar

A meta-analysis found that blood glucose decreased after dry fasting,[6] and another review found similar effects, as well as increased insulin sensitivity.[7]

Decreased inflammation

Dry fasting could help reduce the concentration of inflammatory markers TNF-a, CRP, and IL-6.[8,9] 

That said, a systematic review found that the effects of dry fasting on the immune system were small and temporary.[10] 

Lower cholesterol levels

A study found that dry fasting could improve both LDL and HDL levels.[6] 

Improved bone health

According to one study, dry fasting could have a positive impact on bone health.[11]

Health risks of dry fasting

And, of course, there are risks. 

Nutrient deficiencies

One of the tricky things with dry fasting is making sure you get enough water in during your eating window. 

How easy or tough this is depends on the method of intermittent dry fasting you choose. 

If you did 16:8, for instance, you could drink enough water during your eight-hour eating window. 

But, if you went for a more restrictive fasting schedule like the Warrior Diet, trying to drink enough water in such a short period would take up so much room in your stomach that you wouldn’t be able to eat enough whole, nourishing foods, and that would leave you short on nutrients and energy. 

Dehydration

If you don’t drink enough to replace the water you lose, you become dehydrated. That’s a serious issue that can cause: 

• a buildup of waste in your kidneys (as you’re not excreting it out through the urine) 
• an increased risk of kidney stones and urinary tract infections [12,13]
• slower, more muddled thinking
• low mood 
• headaches 
• dizziness 
• orthostatic hypotension (when your blood pressure drops when you change position and makes you feel faint or unsteady)

In a 2019 study, not drinking water for 36 hours caused fatigue, short-term memory loss, reduced attention, and reduced reaction time.[14]

To make sure you’re hitting your hydration goals (and, more importantly, avoiding those dehydration risks), take our Simple quiz and get your hands on our hydration tracker (as well as a fasting buddy). We’ll send you reminders to drink, so the only thing you’ll have to worry about is whether you’re adding some lemon or mint to that next glass of water.

Hunger

All fasting involves hunger, yet dry fasting makes that hunger harder to handle. 

There are many ways to hack hunger while fasting. One of the best:

Drink water. 

Without that option, hunger will persist longer and feel more intense. 

It’s not just dehydration that leads to fatigue, crankiness, difficulty focusing, and headaches. Hunger can cause all those things, too. 

Is dry fasting safe?

At Simple, we don’t consider dry fasting to be safe. We wouldn’t recommend it as a health improvement practice. 

And there are some groups in particular who should stay away from fasting altogether. If you fall into any of these groups, only fast if you have the support and permission of your doctor:

• you’re extremely active
• your BMI is less than 18.5
• you have (or are at risk of having) an eating disorder or a history of one
• you have a health condition like diabetes or hypothyroid / hyperthyroid
• you’re on medications (especially those that affect blood glucose or blood pressure or need to be taken with food)
• you’re pregnant, breastfeeding, or trying to conceive
• you’re under 18 or 80 years old or older

If you have to avoid fasting or you’re concerned about the safety of dry fasting, don’t worry. There are plenty of safe ways (other easier-to-manage fasting methods included) to lose weight and improve your health. Have a chat with your doctor about what might be right for you. 

Pros and cons of dry fasting

Pros 

Dry fasting isn’t complex to do: remove any liquid intake from your fasting periods, and you’re there. It might help you lose weight and enjoy better health. 

Cons 

Or it may not. There’s not enough evidence to really know whether dry fasting is safe or effective. Any results you see are likely to be short term, and dry fasting can actually damage your health and lead to side effects like fatigue and dizziness. 

Is dry fasting right for you?

You’re the boss of you, and your actions are always your choice. Ultimately, it’s your decision whether to try dry fasting or not. 

Before you decide, check in with yourself:

• Are you fully aware of the risks?
• Are you comfortable with those risks?
• Do you know the signs that mean it’s necessary to break your fast and drink / eat something? 
• Are you confident that intermittent dry fasting would suit you better than regular intermittent fasting? 

If you’re a yes to all these, check in with your doctor. If they agree that it could be a good fasting approach for you, take care and stay tuned in to your body as you fast.

If you’re a no to any of the above points but intermittent fasting sounds good to you, why not try the regular kind — i.e., when you fast, you don’t eat, but you do drink calorie-free drinks. 

Our most recommended fasting schedule is time-restricted eating. 

• Time-restricted eating (TRE)

The most popular options here are:

• 16:8
• 14:10
• 12:12

For each of these, the first number is the amount of hours you’ll fast each day. The second number is the amount of hours you get to eat. With 16:8 intermittent fasting, for example, you’d fast for 16 hours and eat within 8 hours. 

These are simple, accessible options. Great for beginners, especially if you start with 12:12 and work your way up to longer fasts if you feel good. They’re also less prone to introducing pesky side effects alongside any fasting benefits, as you still have plenty of time to hydrate and fill up on nutrients during your eating windows. 

This is particularly relevant if your body is estrogen and progesterone dominant, as you might find that intermittent fasting interacts in a funky way with those hormones. Starting with a shorter fast helps your body adjust better. 

The next four fasting schedules involve 18+ hours of either no eating or limited calorie intake. These schedules can be tricky to manage safely and sustainably, so we usually recommend less restrictive approaches (even if they’re technically less restrictive than dry fasting). 

While we always think it’s a good idea to involve your healthcare team in any changes to your eating habits, if you’re going to give any of the following fasting methods a try, they should definitely be involved in the planning process. 

• The Warrior Diet 

The Warrior Diet involves fasting for 20 hours and eating within four. The hunger can be quite intense, though, and getting all the food you need into that 4-hour time slot isn’t super easy. 

• Alternate-day fasting (ADF) 

Just like it sounds, with alternate-day fasting you eat one day and fast the next. On your fasting days, you’d eat 500/600 calories, so it’s not a total fast, which can make hunger more manageable.

That said, that level of calorie restriction — especially every other day — can be tough to manage without compromising your health and well-being. 

• The 5:2 diet

On the 5:2 diet, you’ll follow a modified fast of eating only 500/600 calories for two days. On the remaining five days of the week, you eat as you usually would. It may be tempting to try a more on / off approach for fasting, but the level of calorie restriction required on those two days is still a toughie. 

• Water fasting

Water fasting is a short fast — 1–3 days tops — where you drink only water and eat no food.

We’ll be honest: if it’s a toss-up between dry fasting vs. water fasting, we’d choose … neither. For fat loss and health benefits, whether you’re male, female, or somewhere else on the sex and gender spectrum, regular intermittent fasting beats both dry and water fasting at delivering better, more long-lasting results and is a safer option that’s kinder to your body and mind.

Written by Trey Reck

Medically reviewed by Josie Porter, RD

Published on | Updated on June 10, 2024