The Truth About 0-Calorie Foods for Fasting – 23 Fasting Foods, Drinks, and Snacks

Do 0-calorie foods for fasting exist, or is it another tall tale filled with wishful thinking? Fasting requires you to abstain from calorie-dense foods, until the eating window. Knowing what are the zero-calorie foods for fasting will help you select your food. Your curiosity is most welcome and recommended.

Truth is, most 0-calorie foods for fasting aren’t absolutely zero calories, but they are so low in calories they may be consumed during a fast, depending on your specific fasting regimen. Some 0-calorie foods are suitable for most fasting programs. Let’s discover the facts about eating 0-calorie foods while fasting. 

Can I Eat 0-Calorie Foods While Fasting?

Sadly, there are no true 0-calorie foods. Some beverages contain a negligible number of calories and can be consumed during almost any fast. Additionally, some low-calorie foods are appropriate for alternate-day or 5:2 diet “fasting” days where people consume around 500 calories or 25% of their energy needs. Some of our top picks include: 

• Instant black coffee (3)
• Unsweetened green tea (16)
• Zucchini noodles (17)
• Cauliflower rice (11)
• Baked fish (15)
• Oatmeal (25)
• Popcorn (30)
• Mixed berries (14)
• Eggs (22)

Wait! There’s a rainbow behind the mythical clouds. Let’s look at the details of “zero-calorie foods for fasting” before disappointment and hunger overwhelm you. 

Zero-Calorie Foods for Fasting: Myth or Fact?

0-calorie foods for fasting are available on a unique fasting schedule called dirty fasting. Dirty fasting is a form of time-restricted eating. On a time-restricted eating schedule, people fast for a certain number of hours each day (commonly 16 hours, overnight) and eat all their meals within a certain number of hours (commonly 8 hours, during the day). Dirty fasting allows a small number of calories, typically around 100, during fasting periods. 

Dirty vs. Clean Fasting

The National Institute on Aging reviewed multiple studies to establish whether or not intermittent fasting has health benefits for humans (28). First, fasting triggers a metabolic switch, where your liver turns fat into ketones for energy, instead of using glucose. 

Also, intermittent fasting is a period of eating normally and fasting, where you eat minimal or no calories, resulting in an overall reduced calorie intake. Some human studies included in the review suggested health benefits, like losing weight and better diabetes management. 

Results are limited because human trials have mostly been conducted on overweight, middle-aged adults, and the long-term effects of intermittent fasting have not been well studied in humans. The included studies looked at various types of intermittent fasting and did not differentiate between “clean” and “dirty” fasting, which are colloquial terms and not scientific categories. 

Another Portuguese meta-analysis found that intermittent fasting improved markers of metabolic conditions (21). They also included studies with various types of intermittent fasting protocols, finding that alternate-day fasting promoted the major beneficial effects in comparison with time-restricted and religious fasting protocols. Alternate-day fasting typically involves some calorie intake (around 500 calories or 25% of energy needs) on fasting days.  

On the other hand, Health explains that the newer dirty fasting trend allows you to eat up to 100 calories while doing time-restricted eating (36). A small randomized controlled trial of 105 individuals found that a 200-calorie specially formulated energy bar didn’t stop the metabolic switch (2). Note, the nutrient bar manufacturer paid for the study.

Let’s go deeper into whether or not foods have zero calories, before wrapping up the debate between clean and dirty fasting. 

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Is There Any Food That Is 0 Calories?

Most foods trigger an insulin response, which is usually what constitutes “breaking” a fast. Insulin is released when there is glucose in the blood which needs to get into the cells to be used as fuel. 

Some individuals use zero or low-calorie sweeteners in coffee or tea during the fasting window. There is some evidence that artificial sweeteners may sometimes illicit an insulin response. 

A small study of 64 overweight individuals by the Department of Nutrition Science in Indiana showed that insulin was released after sucralose was consumed in liquids and solid foods, with a greater insulin response to the sucralose in solid foods (31). Overall evidence is mixed on whether these sweeteners do cause an insulin response and when.  However, the possibility of an insulin response with ingestion of zero- or low-calorie sweeteners while fasting could lead to dangerously low blood sugar levels – a potential adverse effect to look out for. 

On the other hand, a small 10-person study in Oklahoma showed that black, unsweetened coffee didn’t affect fasting blood work values (32). Indeed, some items may not affect your fasting state, even if they have a small number of calories. 

Is There a Snack With 0 Calories?

Most foods don’t come with 0-calorie labels. Instead, you can use low-calorie snacks as part of a dirty fasting schedule, limiting calories to 100 or less during fasts (36). For example, have some popcorn. The USDA shows a cup of air-popped popcorn without oil has 31 calories (30). 

What Food Fills You Up Without Calories?

Low-calorie foods that fill you up include fiber-rich and high-water-content fruits and vegetables. Remember that no food is realistically calorie-free, but some foods help by making you feel full on much lower calories per portion on a dirty fast schedule. 

The Mayo Clinic suggests using low-energy-density fruits and vegetables packed with fiber and water to feel full on very few calories (35). Fiber digests slowly, helping you feel full longer with fewer calories. Meanwhile, a grapefruit is 90% water and has very few calories. 

Fat is high-energy-density but could work in small amounts to keep you full during a fast (35). The USDA shows that a 5-gram pat of unsalted butter has 35.8 calories (6). Bulletproof or butter coffee is a popular go-to for fasting programs. Fat doesn’t elicit an insulin response, so some people allow themselves a small amount of fat while fasting.

However, a cup of bulletproof coffee can have over 300 calories (10). Due to that calorie load, we don’t recommend it, even for dirty fasting. Another nutrient that keeps you full is protein. Harvard U. states that fiber can make you feel full, but a little bit of protein keeps you full longer (23). However, the body can convert excess protein to glucose, which can break your fast if you aren’t careful.

Dirty or Clean Fasting: Which Is Better?

When it comes to “dirty” vs “clean” fasting, this distinction has not been well-studied. “Dirty” fasting is more of a trendy new take on time-restricted eating. 

New evidence has come to light that suggests that time-restricted eating my have long-term adverse effects.. An American Heart Association study on 20,000 individuals over a period of 8-17 years is quickly gaining attention for its controversial abstract (1). 

The study suggests individuals may be at greater risk of death from heart disease following prolonged 16:8 intermittent fasting schedules. However, the study has limitations, such as its reliance on self-reported dietary information, and it did not include other factors in its analysis which could impact health. . 

The Portuguese meta-analysis found that intermittent fasting, especially alternate-day fasting, could improve blood pressure and other markers in obese individuals or those with metabolic syndrome (21). Additionally, a Swedish review found that calorie restriction may also promote improve certain cardiovascular risk factors (7). 

Not enough evidence agrees on how fasting affects the heart and cardiovascular risk factors, especially over the long-term. So, speak to your healthcare provider about your plans to fast if you have heart problems, high blood pressure, or other risk factors. 

Read more: Green Tea Intermittent Fasting: Benefits and Side Effects

What Foods Can I Eat Unlimited Amounts Of?

The 0-calorie foods for weight loss and fasting myth is shattered. However, let’s show you what people realistically mean by zero-calorie foods for weight loss and fasting. None of them allow you to eat unlimited amounts, but you can limit your calories to 100 if you’re following the “dirty” fasting trend. 

6 of the Best “0-Calorie” Drinks for Fasting

Zero-calorie drinks for fasting exist, but many drinks have some calories.

• Water

Tap or well water is the truest zero-calorie food or drink item for fasting. The USDA data shows that any amount of tap or well water has no calories (4). 

• Lemon Water

A 476-gram glass of lemon water has 0.4 calories when diluting ½ teaspoon of lemon juice in a 16 fl oz. bottle of water (13). 

• Apple Cider Vinegar Water

The USDA reports that a tablespoon of apple cider vinegar has 3.13 calories (33). Add one tablespoon of it to a glass of water for an unusual fasting beverage. 

• Black Coffee (Instant)

The USDA suggests a teaspoon of instant coffee powder has 3.53 calories with 0.12 g of protein (3). Make an unsweetened coffee with powder for less than five calories.

• Green Tea

An 12 fl oz. cup of unsweetened green tea has only 4 calories and 0.5 g of protein, to keep you feeling full (16). 

• Black Coffee (Brewed)

An 8 fl oz. cup of brewed breakfast blend coffee has just under 5 calories and 0.74 grams of protein. 

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12 of the Best “0-Calorie” Food List

The zero-calorie foods for intermittent fasting are a list of edible and drinkable items with ultra-low calories per serving. Take careful note of the cooking methods used, serving size, and ingredient limitations, if you’re using these foods during a fast.

• Watercress

 A 34-gram cup of chopped watercress contains 3.74 calories, 0.78 g of protein, 0.03 g of fat, and 0.17 g of fiber (34). 

• Lettuce

A 36-gram cup of shredded lettuce only has 5.4 calories, 0.49 g of protein, 0.05 g of fat, and 0.47 g of fiber (24). 

• Swiss Chard

A 36-gram cup of chopped Swiss chard contains 6.84 calories, 0.65 g of protein, 0.07 g of fat, and 0.58 g of fiber (19). 

• Cucumber

A ½ cup of raw cucumber slices contains 7.8 calories, 0.34 g of protein, 0.06 g of fat, and 0.26 g of fiber (20). 

• Radishes

A ½ cup of sliced, raw radishes contains 9.28 calories, 0.39 g of protein, 0.06 g of fat, and 0.93 g of fiber (27). 

• Zucchini Noodles

A cup of zucchini noodles contains 19 calories, 1.4 g of protein, 0.4 g of fat, and 1.1 g of fiber (17).

• Carrot 

A small 50-gram raw carrot has 20.5 calories, 0.47 g of protein, 0.12 g of fat, 1.4 g of fiber, and 44.2 g of water (18).  

• Cauliflower Rice

A 100-gram cup of cauliflower rice has 25 calories, 1.9 g of protein, 0.3 g of fat, and 2 g of fiber (11). 

• Baked Fish

A 1 oz. boneless, raw pieces of fish baked without added ingredients would contain 33 calories, 5.1 g of protein, and 1.2 g of fat (15). 

• Bone Broth

WebMD suggests a cup of beef bone broth made with beef stock has 39 calories, 9 g of protein, and 1 g of fat (5). 

• Lean Beef Mince

A single ounce of lean beef mince prepared without any other ingredients has 54.7 calories, 8.3 g of protein, and 2.1 g of fat (12). Fortunately, a pinch of table salt adds no calories (29).  

• Oatmeal

A 100-gram serving of oatmeal cooked in water without salt contains 71 calories, 2.5 g of protein, 1.5 g of fat, and 1.7 g of fiber (25). 

Read more: Intermittent Fasting and Running: A Winning Combination or a Terrible Mistake?

5 of the Best “0-Calorie” Snacks for Fasting

Zero-calorie snacks for fasting are actually low-calorie snacks you can enjoy on a so-called dirty fast (36). Be sure to follow the recommended types and portions, including using air-popped as a cooking method for popcorn, or boiling for eggs to ensure you don’t add more calories.

• Popcorn

An 8-gram cup of air-popped popcorn has 31 calories, 1.03 g of protein, 0.36 g of fat, and 1.16 g of fiber (30). 

• Mixed Berries

A ½ cup of mixed berries contains 32.5 calories, 0.7 g of protein, 0.3 g of fat, and 2.8 g of fiber (14). 

• Rice Cakes

A single rice cake has 35 calories, 0.7 g of protein, 0.3 g of fat, and 0.4 g of fiber, to keep you satisfied with a small snack during a fast (8). 

• Oranges

A small 96-gram orange has 45.1 calories, 0.9 g of protein, 0.12 g of fat, and 2.3 g of fiber ideal for an on-the-go fasting snack (26). It also has 83.3 grams of water. All water-dense, fiber-rich fruits are good fasting snacks.

• Boiled Eggs

USDA data shows that a large hard-boiled egg has 77.5 calories, 6.3 g of protein, and 5.3 g of fat, making it another on-the-go snack idea (22).  

For more fasting tips and information:

• Can I use stevia while fasting?
• Fasting vs. starving
• Vegetable broth for fasting

FAQs

• What Is the Best Food for Fasting?

The best food for fasting includes ultra-low-calorie foods, if you decide to eat a small number of calories during a fast. Some top choices with the fewest calories include watercress (3.74), lettuce (5.4), Swiss chard (6.84), cucumber (7.8), and radishes (9.28) (34, 24, 19, 20, 27). 

• What Is Dirty Intermittent Fasting?

Health, explains that the newer dirty fasting trend is a form of time-restricted eating that allows you to eat up to 100 calories during fasting periods (36). “Clean” intermittent fasting includes time-restricted eating plans where you eat little but preferably no calories during fasting times (21). 

• What’s the Lowest-Calorie Snack?

One of the lowest-calorie snacks is popcorn. An 8-gram cup of air-popped popcorn has 31 calories  (30). However, salted cucumber slices are possibly the lowest-calorie veggie snack. A ½ cup of cucumber slices has 7.8 calories, while a pinch of salt adds no extra calories (20, 29). 

The Bottom Line

Our top 23 “0-calorie foods for fasting” aren’t all calorie-free, but they do provide you with enough fiber and water to keep you full and with very few calories. You can consume calories during a fast if you battle with hunger pangs. Some types of fasting allow a limited number of calories during fasting times. The low-calorie foods on this list are perfect for those times.