By the Live Fitness Check editorial team • Reviewed for accuracy
Does black coffee break a fast? What about gum, lemon water, or that splash of cream? These questions flood every fasting forum because the internet cannot agree on the answer. Here is the plain-English rule most fasting coaches use: anything with real calories breaks a fast; anything with effectively zero calories does not. Below is the rapid-fire yes/no list, plus the famous 50-calorie rule explained properly. Want to plan around your own schedule? Start with our free intermittent fasting calculator to map your eating and fasting hours first.
Calories break a fast. Black coffee, plain tea, water, and sparkling water (all near-zero calories) do not. Cream, sugar, milk, juice, smoothies, and bone broth (50+ calories) do. Diet soda and gum are gray areas — zero calories, but they can spike hunger for some people. A common rule of thumb is that anything under about 50 calories won't meaningfully ruin the metabolic state, but purists treat any calories as a break. Medications are the one non-negotiable: always take them as prescribed, fasting or not.
Calculate My Fasting WindowYou will see "stay under 50 calories" everywhere in fasting communities. Here is what it actually means: the benefits of fasting — appetite control, lower insulin, the convenience of fewer meals — do not switch off like a light at calorie number one. A splash of milk (~10–20 calories) or a stick of gum (~5–10 calories) does not produce a meaningful insulin response in most people, so it will not undo your day. That is the practical truth behind the rule.
But treat it as a ceiling, not a budget. Nobody gets fasting benefits from 49 calories of creamer "because it's under 50." And if your goal is strict autophagy-focused fasting rather than simple weight-loss fasting, the honest answer is zero calories is safest — the research on tiny calorie amounts and autophagy is thin. For weight loss, the pragmatic standard is: keep it under ~50 calories and preferably under ~10, and never drink your calories on purpose during a fast.
| Item | Verdict | The logic |
|---|---|---|
| Water (still/sparkling) | No | Zero calories. Drink more than you think you need. |
| Black coffee | No | ~2–5 calories per cup — effectively zero; also blunts hunger. |
| Plain tea (green, black, herbal) | No | Zero calories unsweetened. |
| Lemon or lime water | No | A squeeze is ~5 calories — well under the line. |
| Apple cider vinegar (1 tbsp in water) | No | ~3 calories; may even help blood sugar. |
| Diet soda / zero-cal drinks | Technically no | Zero calories, so it doesn't break the fast on paper. But artificial sweeteners can trigger hunger or cravings in some people — if it makes fasting harder, drop it. |
| Sugar-free gum | Technically no | ~5–10 calories per stick; negligible. Same caveat as diet soda: if chewing makes you hungrier, skip it. |
| A splash of milk in coffee | Gray area | ~10–20 calories per tablespoon. Under the 50-calorie rule, purists say it breaks it, pragmatists say it doesn't matter. Decide which camp you're in. |
| Cream / half-and-half in coffee | Yes | ~20–50 calories per tablespoon; two splashes and you're past the line. |
| Sugar or honey in coffee/tea | Yes | A teaspoon of sugar is ~16 calories and spikes insulin — the thing fasting is trying to avoid. |
| Bone broth | Yes | 30–80 calories per cup plus protein; it will nudge insulin. Save it for your eating window. |
| Bulletproof/butter coffee | Yes | 100–200 calories of fat. That is a meal, not a fast. |
| Smoothies, juice, lattes | Yes | Obvious calories — 100+. |
| Alcohol | Yes | ~100 calories per drink plus it tanks judgment and sleep. |
Always take your medication exactly as prescribed — fasting never outranks a prescription. If a pill must be taken with food, take it with food and adjust your fast around it. This matters most for blood-sugar drugs (insulin, sulfonylureas), blood-pressure medication, and anything with "take with food" on the label. If you are unsure how fasting interacts with your prescriptions, ask your doctor or pharmacist before you fast — not after you feel dizzy.
The same applies to vitamins and supplements. A multivitamin is ~0–10 calories and won't meaningfully break a fast, but fat-soluble vitamins (A, D, E, K) absorb better with food, so most people just take them in the eating window.
Here is the part fasting forums won't tell you: accidentally eating 50 calories at 10 am does not delete your progress. Intermittent fasting works because the weekly pattern makes it easier to eat less overall — one early snack is a blip in a pattern of dozens of clean fasts. The dangerous response is the guilt spiral: "I broke it, so today is ruined, so I might as well eat everything." That turns 50 calories into 1,500. If you slip, you note it and resume your normal window. The fast resumes tomorrow; the only way to truly fail is to quit the pattern.
Remember what the fasting is for. If your goal is weight loss, the eating window is where results are decided. Find your maintenance calories with the TDEE calculator, set a 300–500 calorie deficit, and check the plan against the calorie deficit calculator. A clean 16-hour fast followed by a 1,000-calorie surplus dinner is still a surplus. For the full beginner walkthrough of schedules, drinks, and who should skip fasting, see our 16:8 intermittent fasting guide.
Disclaimer: This article is for general information only and is not medical advice. Talk to your doctor before starting a new diet or exercise program, especially if you are pregnant, have a medical condition, or take medication.
