Does It Break a Fast?

Search a food or drink and get three answers, not one — because a strict fast, a fat-loss fast and an autophagy fast do not draw the line in the same place. Calories, the reason, and the honest gray zones.

Search a food or drink

128 foods and drinks, at the serving people actually use — a splash, a teaspoon, one packet.

Nothing in the list matches that.

This is a curated list rather than a search of every food in existence, so the rule of thumb has to cover the rest: if it has calories, it breaks a strict fast. If it has protein, it breaks an autophagy fast. If it is under about ten calories with no protein and almost no carbohydrate, it will not stop fat loss. Try the closest thing on the list, or read the long answer.

The full answer

How to read this

Three fasts, three lines

"Does it break a fast" has no single answer, because the word means three different things to the three people asking it. Every item here is judged three times, and each column says which definition it is using.

Doesn't break it. Nothing to burn and nothing to store — the answer is a plain no.

Technically yes, and it's nothing. There are calories in it, so a strict fast counts them. They are far too few to move insulin or stop fat burning, and saying so is more useful than forcing a yes or a no.

Not settled. The calories are not the question here, and the question that matters does not have an agreed answer yet. Both sides of the argument are on the card.

Breaks it. Enough energy, protein or sugar to end the fast on that definition.

Nothing on this page is a verdict somebody typed. Each one falls out of the item's published numbers through the thresholds set out below, which is why the numbers are printed next to every answer — a figure can be checked against a source, and an opinion cannot.

The full answers

Every "does it break a fast" guide on this site

The verdict above is the short answer. Where an item has a page of its own — the evidence, the gray zones, and what changes if you are fasting for a different reason — it is here.

Still not sure what counts? What breaks a fast is the long answer, and the extended fast planner covers the same question over 24, 48 and 72 hours, where the stakes are higher.

Where the numbers come from

Every verdict starts from published nutrition data, not from opinion. Calories, protein, carbohydrate and fat per serving come from the USDA FoodData Central database, and the serving sizes are the ones people actually use — a splash of milk, a teaspoon of sugar, one packet of sweetener. From there the tool applies three thresholds, and it tells you which one it is using. Strict fast: anything with measurable calories breaks it, full stop, because the only unambiguous definition of a fast is zero energy intake. Metabolic fat loss: the question is whether the item is large enough to raise insulin meaningfully, so items under roughly 10-15 calories with no protein and little carbohydrate are marked as trivial rather than breaking. Autophagy: protein and total energy matter most, because leucine and insulin both suppress the pathway, so the bar sits lowest here. Where the honest answer is "technically yes, metabolically almost nothing", the tool says exactly that instead of picking a side. The autophagy thresholds are the softest numbers on the page: autophagy in humans cannot be measured outside a lab, and the fasting durations that trigger it are estimated from a small literature, so treat that column as a considered guess rather than a measurement.

Curated client-side dataset built from USDA FoodData Central published values. Live-API mode is gated on services.usda.api_key being set.

Sources

1. FoodData Central — U.S. Department of Agriculture, Agricultural Research Service
2. Effects of Intermittent Fasting on Health, Aging, and Disease — de Cabo & Mattson, New England Journal of Medicine, 2019 (PubMed)
3. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting — Anton et al., Obesity, 2018 (PubMed Central)
4. The Nobel Prize in Physiology or Medicine 2016 — Yoshinori Ohsumi, for discoveries of mechanisms for autophagy — The Nobel Foundation

Nothing on this site is medically reviewed — it cites its sources so you can check them. Read our editorial policy.

Why one answer was never going to work

Type "does cream break a fast" into a search box and you get a wall of pages that all answer confidently and half of them disagree. That is not because the writers are careless. It is because they are answering different questions and none of them says which. A person fasting for a blood test, a person fasting to lose weight and a person fasting because they read about autophagy are asking three different things, and the tablespoon of cream is fine for one, marginal for the second and out of the question for the third.

So this tool answers all three separately. The strict column is the only one with a clean edge: a fast is a period of no energy intake, so anything with calories in it breaks the fast, and there is nothing to argue about. The fat-loss column asks a different question — whether the item is enough to raise insulin and interrupt fat burning — and at a few calories with no protein and almost no carbohydrate the honest answer is that it makes no practical difference. The autophagy column sits lowest of the three, because protein appears to be the specific off-switch: leucine signals through mTOR, and mTOR suppresses the pathway. That is also the column to trust least, and the page says so rather than burying it: the mechanism is clear in cells and in mice, no human trial has tested a small dose in a fasted person, and nobody has established the amount that matters. Any page giving you a gram figure for when autophagy stops has made it up.

The numbers themselves come from published USDA FoodData Central values, matched to servings people actually use. That last part matters more than it sounds. Most nutrition data is published per 100 grams, and nobody puts 100 grams of cream in a coffee. A tablespoon of heavy cream is about fifty calories; a teaspoon is about seventeen. Those two answers land on opposite sides of "does this matter", and a table of per-100-gram figures gives you neither.

The gray zones are the part most tools skip. A "zero calorie" sweetener packet is usually not zero. US labelling rules say a serving under five calories may be printed as zero, and a serving under half a gram of carbohydrate may be too — and the bulking agent in a sachet is normally about a gram of dextrose, which lands inside both windows. USDA analysed a sucralose packet and got 3.4 calories and 0.9 grams of carbohydrate. The label is accurate. It is just not literally zero, and the tool says so rather than repeating the front of the packet. Erythritol is the honest exception: the same rules set it at zero calories a gram outright, so a packet bulked with erythritol really is nothing while one bulked with dextrose is not, behind identical front-of-pack wording.

One last thing worth saying out loud: for most people, most of the time, the strict column is not the one that decides anything. If you are fasting to lose weight, a splash of almond milk in your coffee will not undo your morning, and treating it as a failure is the fastest way to give up on something that was working. Use the column that matches why you are fasting, and let the other two be interesting rather than binding.

Which column applies also depends on how long the fast is. Over a day the question changes from "does this count" to "am I doing this safely" — that is what the extended fasting guide and the extended fast planner are for. And if you are still deciding where to run the clock, the best intermittent fasting app in 2026 comparison covers the field, ours included, with its gaps named.

Frequently Asked Questions

What actually counts as breaking a fast?

It depends entirely on why you are fasting, which is why one answer never fits. If you are fasting strictly, any calorie breaks it — that is the only definition with a clean edge. If you are fasting for fat loss, what matters is whether the item raises insulin enough to interrupt fat burning, so a few calories with no protein or sugar changes very little. If you are fasting for autophagy, the bar is lowest of all, because protein in particular appears to switch the process off. This tool answers all three separately instead of pretending there is one line.

Does coffee break a fast?

Black coffee has close to zero calories and does not break a fast under any of the three definitions. What breaks it is what people put in it. A splash of milk, a spoon of sugar, a scoop of collagen or a pat of butter all carry real calories, and the tool shows you how many for the amount you actually use rather than for a theoretical serving.

What is a "technically breaks it, metabolically trivial" verdict?

Some items carry a handful of calories — a stick of gum, a squeeze of lemon, a splash of cream in a large coffee. They are not zero, so under a strict fast they break it and the tool says so. But they are far too small to meaningfully raise insulin or stop fat burning, so under a fat-loss fast the honest answer is that it makes no practical difference. Saying that out loud is more useful than forcing a yes or a no.

Do artificial sweeteners break a fast?

Most have no calories, so under a strict-calorie definition they do not. The open question is whether sweet taste alone triggers an insulin response, and the evidence there is mixed and depends on the specific sweetener. The tool flags these as a gray zone rather than claiming certainty, and points you at the article on the specific sweetener where one exists.

Where do the calorie numbers come from?

Published values in USDA FoodData Central, matched to the serving people actually use — a splash, a teaspoon, one packet — rather than a 100-gram lab portion. The full method and its sources are set out in our editorial policy.

Does It Break a Fast?

Three fasts, three lines

Every "does it break a fast" guide on this site

Sources

Why one answer was never going to work

Frequently Asked Questions

Go deeper

What Breaks a Fast? The Definitive Answer

What Can You Drink While Fasting? The Complete List

Can You Drink Coffee While Fasting?

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