When you begin a fasting routine, the most important question is often, “What can I drink without breaking the fast?” The short answer is simple: any beverage that contains little to no calories. Water, sugar‑free electrolyte drinks, black coffee, plain tea and sparkling water all fit that description and can keep you hydrated while you reap the metabolic benefits of fasting.

Why Hydration Matters During a Fast

During the early hours of a fast your body depletes stored glycogen, a process that also increases sodium excretion. The result can be a noticeable loss of fluid, which may cause headaches or fatigue for some people. Replacing both water and electrolytes helps you stay comfortable and supports the fast’s intended effects.

Zero‑Calorie Beverages That Won’t Disrupt Your Fast

• Water – The gold standard. Drinking to thirst keeps most people in the “just right” range of fluid intake.
• Sugar‑free electrolyte water – Useful on longer fasts when sodium loss is higher. Check the label for added sugars; many brands contain only a few calories.
• Black coffee – Typically about five calories per cup. It also provides antioxidants and may modestly support autophagy, according to laboratory studies.
• Plain tea – Black, green or herbal teas usually contain around two calories per cup and are rich in antioxidants.
• Sparkling water – Carbonated, calorie‑free water can add variety without breaking the fast.

What About Diet Soda and Artificial Sweeteners?

Zero‑calorie sodas sweetened with stevia or monk fruit are technically acceptable, but some research suggests certain artificial sweeteners could affect gut microbiota. The evidence in humans is mixed, so if you’re concerned, stick with plain water or unsweetened tea.

When Small Calories Might Be Acceptable

Strictly speaking, any calories end a zero‑calorie fast. However, many people follow modified fasting protocols that allow tiny amounts of fat or collagen without significantly impacting weight‑loss or metabolic goals. If you choose this route, keep the intake minimal and understand it is no longer a pure zero‑calorie fast.

How Fasting Affects Hormones

Fasting lowers insulin and mTOR signaling, shifting the body from growth‑focused pathways to those that burn stored fat. This hormonal shift can improve certain metabolic markers and support weight loss when overall calorie intake drops. Remember, occasional rises in insulin after a meal are normal and not a health threat unless they become chronic.

Practical Tips for Staying Hydrated

• Listen to your body’s thirst cues rather than chasing a specific ounce target.
• If you feel light‑headed, increase water intake gradually.
• On longer fasts, consider an electrolyte drink with zero or very low calories.
• Avoid adding cream, milk, sugar or high‑calorie flavorings to coffee or tea.

In summary, the safest drinks for a fast are those that contain little to no calories. By staying hydrated with water, electrolyte water, black coffee, plain tea or sparkling water, you can maintain comfort and support the metabolic benefits that fasting aims to provide.

Original reporting: KEYT (Ventura/Santa Barbara) — read the source article.