Does Sparkling water break a fast?
Does not break a fast
Sparkling water does not break a fast when used as directed — its calorie and insulin impact is negligible for standard fasting goals.
Goal-based reading
Fasting goals differ. Use this matrix as a conservative reading of the same item-specific verdict; the detailed note and source below carry the nuance.
| Goal | How to read this verdict |
|---|---|
| Weight loss / calories | Usually compatible when calories are negligible. |
| Metabolic / insulin | Usually compatible when insulin impact is negligible. |
| Gut rest / strict fast | Plain water is still the strictest choice; use only if your protocol allows it. |
| Autophagy / longevity | Evidence is limited; plain water is the conservative choice. |
Calories
0 kcal (plain carbonated water, no flavourings or sweeteners)
Why — the calorie and insulin logic
Plain carbonated water — water with CO₂ — contains zero calories, sugar, protein, or fat. For fasting purposes, the carbonation does not change the calorie or insulin logic.
Does it depend on your fasting goal?
Safe for standard fasting goals when it is plain and unsweetened. Check flavoured sparkling waters for sugar, juice, or calories. Sweetened sparkling drinks such as tonic water break a fast.
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Frequently asked questions
- Does sparkling water break intermittent fasting?
- No. Plain sparkling water has zero calories and does not affect insulin. Choose unflavoured, unsweetened varieties to stay completely fast-safe.