What to Drink While Intermittent Fasting, What Breaks a Fast, and What the Evidence Shows
You can drink water, plain black coffee, plain tea, sparkling water, and unsweetened electrolytes while intermittent fasting. Anything with calories, sugar, protein, or fat breaks the fast, so skip juice, soda, milk, cream, and any coffee drink built on syrup. That holds for 16:8 fasting and most other protocols. The real questions come next: does coffee break a fast, why you feel bad by mid-afternoon, and what you can take without undoing it. This guide answers those in order and reports what the trials found, including results that undercut fasting marketing.
What You Can Drink While Fasting
What to drink while intermittent fasting comes down to a short safe list, and that is good news.
- Water, still or sparkling
- Plain black coffee
- Plain tea, black, green, or herbal
- Unsweetened electrolytes with zero calories
- Diluted apple cider vinegar, if you tolerate it
Coffee and tea carry caffeine, which most people handle fine mid-fast.
| Drink | Breaks a fast? | Why |
|---|---|---|
| Water | No | No calories |
| Black coffee | No | Almost no calories |
| Unsweetened electrolytes | No | Minerals only |
| Coffee with cream | Yes | Fat and protein |
| Coffee with sugar | Yes | Sugar |
| Juice | Yes | Sugar |
| Milk | Yes | Sugar and protein |
| Bone broth | Yes | Protein |
| MCT oil in coffee | Yes | Fat |
If it has calories, it breaks the fast. The only real argument is over amounts so small they round to zero.
What Breaks a Fast
A fast breaks when you take in energy. That is the whole rule. The confusion is where energy hides.
Drinks That Break a Fast
- Juice, including cold-pressed and "no added sugar" versions
- Regular soda and sweetened iced tea
- Milk, oat milk, and most plant milks
- Coffee with cream, milk, butter, or MCT oil
- Smoothies and protein shakes
- Kombucha, which carries sugar even when it tastes sour
Foods That Break a Fast
Any food breaks a fast, and the amount barely matters.
- Nuts and seeds
- Cheese and dairy
- Fruit, even a few berries
- Any bar, even a "fasting" bar
- Gum with sugar, and mints
Sugar-free gum is a gray area: low in calories, but it can trigger hunger in some people.
Supplements That Break a Fast
This is where most people break a fast without knowing it.
- Gummy vitamins and gummy electrolytes, built on sugar
- Fish oil and any softgel suspended in oil
- Protein powder, collagen, and amino acid blends
- Anything labeled a shake or meal replacement with calories
A plain capsule is different. A hard capsule with a mineral inside carries no calories.
Does Coffee or Tea Break a Fast
No. Black coffee and plain tea do not break a fast.
Plain black coffee runs roughly two to five calories a cup, and plain tea is close to zero. Many practitioners use a rough threshold of about 50 calories for what might not interrupt a fast, though no trial has tested where that line actually falls. Coffee also suppresses appetite, which is why so many routines lean on it.
Does Cream or Milk in Coffee Break a Fast
Yes. Heavy cream carries fat, and milk carries fat and sugar as lactose.
Even a small splash adds calories and protein, which is what a fasting window is trying to avoid. A splash of unsweetened plant milk is smaller but still not zero. For a clean fast, drink it black.
What About Sweeteners in Coffee or Tea
It depends on the sweetener.
- Sugar, honey, agave, and maple syrup all break a fast
- Artificial sweeteners like sucralose carry no calories, but some researchers question whether they affect insulin
- Stevia and monk fruit are calorie-free and widely used by fasting communities
For flavor with no calories, stevia is the common choice. Caffeine on an empty stomach can bring jitteriness or acid reflux.
What the Evidence Actually Shows
The trials here are more mixed than the marketing suggests.
The Trials That Found Little Difference
The strongest test of fasting against a fair comparison found no advantage.
The TREAT trial followed 116 adults with overweight or obesity for 12 weeks. One group ate in a 16:8 window; the other ate three structured meals. The fasting group lost 0.94 kg, and the difference between groups was not statistically significant. The fasting group lost significant lean mass, roughly 65 percent of the weight it lost, while the control group's lean-mass change was not statistically significant. That undercuts the idea that fasting protects muscle.
A 2026 meta-analysis by Fernandes-Alves and colleagues pooled 30 studies and 1,341 participants. Against controls that were not calorie matched, time-restricted eating cut weight by 2.82 kg and also cut fat-free mass by 0.86 kg. Against isocaloric controls, meaning equal calories, the weight advantage was roughly halved and no longer meaningful on its own. Much of the weight loss people credit to fasting appears to come from eating less, not from timing.
The Trials That Found an Advantage
Other trials show a real edge, usually when timing is paired with a calorie target.
The TREAD trial followed 61 adults with obesity for 12 weeks on a 10-hour window. The fasting group lost 4.59 kg against 1.68 kg in standard care, a difference of 2.91 kg that came mostly from body fat.
Jamshed and colleagues studied 90 adults with obesity over 14 weeks. Early time-restricted eating, an 8-hour window from 7:00 to 15:00, plus energy restriction beat energy restriction alone by 2.3 kg. Body fat did not differ significantly.
Martinez-Montoro and colleagues randomized 160 adults for 3 months, with every arm calorie restricted. Late time-restricted eating beat control by 2.27 kg. Early time-restricted eating did not separate from control, at 1.22 kg with a confidence interval that crossed zero.
Camacho-Cardenosa and colleagues followed 99 adults for 12 months after a 12-week program. Early and late time-restricted eating both maintained greater weight loss than usual care.
Wong and colleagues pooled 23 randomized trials and 1,280 participants. The 16:8 pattern produced small reductions in fasting glucose, HOMA-IR, and insulin. The effects were modest.
He and colleagues pooled 22 studies and 1,287 women. BMI and fasting glucose fell, but blood pressure did not change significantly.
One 8-week trial put both groups through supervised aerobic and resistance training. The group that also ate inside a time-restricted window lost 9.0 percent of its fat mass, against 3.3 percent in the normal-eating group.
What Holds Up, and What Does Not
- Timing alone, with no calorie control, produces little extra weight loss
- Timing plus a calorie target tends to produce a small edge
- Fasting does not reliably protect lean mass on its own. An 8-week trial in 68 women found the fasting-only group lost significant total lean mass
- When resistance training is part of the program, lean mass is preserved or increases
If weight and metabolism are your main reason for fasting, treat the window as one tool among several.
Why Fasting Makes You Feel Bad
Headache, fatigue, dizziness, and cramping are the most common complaints during a fast. Most trace back to fluid and minerals, not to a deeper cleansing process.
The Mineral Shift
When you stop eating, you stop taking in the dietary sodium, potassium, and magnesium that food supplies, while fluid losses continue.
The ketogenic diet literature documents the same shift: when carbohydrate intake collapses, water and electrolyte balance becomes a recognized pathway, and reviews flag the need to ensure adequate potassium and magnesium.
The Honest Caveat on Electrolytes
Here is where fasting marketing outruns the data.
A 2025 study by Yacoub and colleagues measured salivary pH, flow rate, and electrolytes in 27 healthy men during Ramadan fasting. Fasting changed salivary calcium and pH, but it did not significantly change sodium, potassium, chloride, or phosphate. The measured electrolyte data in fasting is thinner than supplement brands imply. Your body runs its own detox and methylation pathways around the clock, fasting or not.
Headache
First-day headaches usually come from caffeine withdrawal and dehydration. If you cut coffee along with meals, the headache may be caffeine, not fasting.
Fatigue and Dizziness
Lightheadedness when you stand points to low blood volume, a fluid and sodium issue. Ongoing fatigue is more often about under-eating in your window. If brain and memory sharpness drops, track it across a full week.
Muscle Cramps
Cramps usually point to sodium, potassium, or magnesium. Sodium is the one people miss, because heart and circulation advice to cut salt was written for a fed state.
A 2025 review by Guo and colleagues reported the honest side of the ledger. Across 15 studies and 929 participants, fasting lowered systolic blood pressure by 4.43 mmHg and diastolic by 2.00 mmHg versus control. Higher rates of vomiting and irritability also appeared, mostly early and self resolving. Those are measured trial outcomes, reported as findings, not claims about any product.
What You Can Take Without Breaking the Fast
This is the question a supplement retailer can actually answer, and almost nobody does.
These do not break a fast:
- Plain electrolytes. Sodium, potassium, and magnesium in an unsweetened, calorie-free powder or capsule
- Magnesium. Capsules or a plain powder, in forms like magnesium glycinate or citrate
- Plain mineral and vitamin capsules. A hard capsule with no oil and no sugar, like a plain multivitamin capsule
These do break a fast:
- Gummy electrolytes and gummy vitamins, built on sugar
- Softgels suspended in oil, including fish oil
- Anything with protein, collagen, or amino acids
Agape Nutrition carries practitioner-grade electrolytes and minerals in capsule and powder form. Look for zero calories, no sugar, and no oil on the label.
The test is simple: if it ends in "ose" or lists calories, it breaks the fast.
How to Break a Fast
How you break a fast matters more than most people expect. Eat a heavy meal straight out of a long fast and you will feel bloated, sleepy, and uncomfortably full.
- Start small with broth or a few bites of protein
- Wait 20 to 30 minutes before your main meal
- Build that meal around protein, vegetables, and healthy fat
- Keep refined carbs and sugar low in the first meal
- Drink water with the meal, and add electrolytes if you felt symptoms
Breaking a fast with a sugar load is a common mistake. A high-sugar first meal can push blood sugar up and then down, which leaves many people feeling worse than they did mid-fast.
For digestion support as you return to normal meals, Agape's digestion and gastrointestinal collection covers options worth a look.
Why the First Meal Matters
A protein-forward first meal tends to keep energy steadier. A sugar-forward one can set up a crash and a craving cycle.
Who Should Not Fast
Fasting is not safe for everyone, and the list is longer than most guides admit. If any of these apply, talk to your doctor first.
- People who are pregnant or breastfeeding
- Children and teenagers who are still growing
- Anyone with a history of an eating disorder
- People with type 1 diabetes, or type 2 diabetes managed with insulin
- Anyone taking medication that must be taken with food
- People who are underweight or losing weight without trying
Only your prescriber can tell you how to time medication around a fast. If you feel faint, confused, or unwell mid-fast, eat something.
What We Recommend
Pure Essence, Ionic-Fizz Magnesium Plus Mixed Berry Flavor
A zero-calorie ionic mineral powder that dissolves into a flavored drink carrying 300 mg magnesium, 100 mg potassium, and a full ionic sea mineral and trace mineral profile, so you replace the minerals a fasting window drains without taking in any calories, sugar, or oil.
$34.11
Integrative Therapeutics, Magnesium Glycinate Plus 120 Tablets
A plain, oil-free tablet built on fully reacted magnesium chelated to glycinate, lysinate, and aspartate, the well-absorbed forms the guide points to, and it tends to be easier on the gut than magnesium oxide or citrate.
$29.25
Researched Nutritionals, Physician’s Daily™ Multivitamin + D3 60 Capsules
An iron-free once-daily multivitamin in a hard capsule with no sugar and no oil, delivering methylated B12 and folate plus 2,000 IU of vitamin D3 so a fasting window does not quietly cost you your baseline vitamins.
$59.98
References
- Lowe DA, Wu N, Rohdin-Bibby L, et al. Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Internal Medicine. 2020. doi:10.1001/jamainternmed.2020.4153
- Jamshed H, Steger FL, Bryan DR, et al. Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial. JAMA Internal Medicine. 2022. doi:10.1001/jamainternmed.2022.3050
- Fernandes-Alves D, Teixeira GP, Guimaraes KC, Crispim CA. Systematic Review and Meta-analysis of Randomized Clinical Trials Comparing Time-Restricted Eating With and Without Caloric Restriction for Weight Loss. Nutrition Reviews. 2026. doi:10.1093/nutrit/nuaf053
- Wong PS, Wan K, Dai Z, Yu AP, Wong SH, Poon ET. Effect of 8-Hour Time-Restricted Eating (16/8 TRE) on Glucose Metabolism and Lipid Profile in Adults: A Systematic Review and Meta-Analysis. Nutrition Reviews. 2026. doi:10.1093/nutrit/nuaf206
- Wilkinson MJ, Padilla E, Wang Y, et al. Time-Restricted Eating Promotes Weight Loss and Favorable Changes in Adipose in Obesity: The TREAD Randomized Control Trial. Obesity. 2026. doi:10.1002/oby.70228
- Martinez-Montoro JI, Bandera B, Gutierrez-Bedmar M, et al. Effect of a ketogenic diet, time-restricted eating, or alternate-day fasting on weight loss in adults with obesity: a randomized clinical trial. BMC Medicine. 2025. doi:10.1186/s12916-025-04182-z
- Camacho-Cardenosa A, Merchan-Ramirez E, Clavero-Jimeno A, et al. Effects of an early, late, and self-selected time-restricted eating intervention on weight loss maintenance in adults with overweight or obesity: A 12-month follow-up. Clinical Nutrition. 2026. doi:10.1016/j.clnu.2026.106706
- Guo Y, Lu L, Chen L, Wang Y, Zhao F, Jiang Y. Effectiveness and safety of intermittent fasting on blood pressure in adults with overweight or obesity: a systematic review. International Journal of Obesity. 2025. doi:10.1038/s41366-025-01823-4
- He H, Qin Z, Liu K, Wang Z, Wang J. The effects of intermittent fasting on BMI, fasting blood glucose, and blood pressure in women with overweight or obesity: a systematic review and meta-analysis with dose-response analysis. Frontiers in Nutrition. 2026. doi:10.3389/fnut.2026.1818813
- Chen S, Kortas J, Ren Y, Zhou H, Liu H. Effects of an 8-Week Time-Restricted Eating and Walking Exercise on Regional Fat Distribution and Lean Mass in Women with Hidden Obesity: A Randomized Controlled Trial. Healthcare. 2026. doi:10.3390/healthcare14121768
- Kotarsky CJ, Johnson NR, Mahoney SJ, et al. Time-restricted eating and concurrent exercise training reduces fat mass and increases lean mass in overweight and obese adults. Physiological Reports. 2021. doi:10.14814/phy2.14868
- Yacoub S, Khemiss M, Besbes A, Ben Saad H. Impact of Ramadan Intermittent Fasting on Salivary pH, Flow Rate, and Electrolyte Levels in Healthy Adult Men. American Journal of Men's Health. 2025. doi:10.1177/15579883241312396
- Rodzen L, Dynka D, Rodzen M, et al. The Ketogenic Diet in the Prevention and Treatment of Hypertension (HTN). Biomedicines. 2026. doi:10.3390/biomedicines14081728
Frequently Asked Questions
Does coffee break a fast?
No. Plain black coffee has almost no calories and does not break a fast. Cream, milk, sugar, or MCT oil does, so keep it black for a clean window.
What breaks a fast?
Anything with calories. That includes juice, milk, bone broth, protein shakes, gummy vitamins, and any food, even a small bite. Water, black coffee, plain tea, and unsweetened electrolytes do not.
Do electrolytes break a fast?
Unsweetened, calorie-free electrolytes do not break a fast. They supply sodium, potassium, and magnesium with no energy. Gummies and any powder with sugar or calories do.
What should I eat to break a fast?
Start small with broth or a few bites of protein, wait 20 to 30 minutes, then eat a meal built on protein, vegetables, and healthy fat. Keep sugar and refined carbs low to avoid a crash.
Is 16:8 intermittent fasting effective for weight loss?
The trials are mixed. TREAT found no significant difference between a 16:8 window and three structured meals over 12 weeks, and a meta-analysis found the weight advantage is roughly halved against matched-calorie controls.
Is intermittent fasting safe for women?
Trials in women have found reductions in BMI and fasting glucose. A 2026 review of 22 studies and 1,287 women found no significant change in blood pressure. Women who are pregnant, breastfeeding, or have a history of an eating disorder should not fast.
What are the most common intermittent fasting side effects?
Headache, fatigue, dizziness, and muscle cramps are most common. A review of 15 studies also found higher rates of vomiting and irritability, mostly early and self resolving.