Yes, cucumber technically breaks a fast, though it is one of the lightest foods there is. A cup of sliced cucumber has about 16 calories and 2 g of sugar, and a whole cucumber about 45. For a weight-loss fast the impact is small; a strict fast is over.
| Calories | ~16 kcal per cup |
|---|---|
| Breaks a weight-loss fast? | Partial |
| Breaks ketosis? | No |
| Breaks autophagy? | Yes |
| Insulin impact | Low |
Cucumber is about 95% water, yet it is still food: it brings a little carbohydrate, fiber and chewing, which start digestion. Any food ends a clean fast, even if the calories are tiny.
Slices left in a jug of water add flavor and almost no calories, so cucumber water keeps a fast. Pickled cucumbers are another case: see our page on pickles for salt and brine.
If hunger is hard to handle on a weight-loss fast, a few slices are a gentle choice. On a clean or autophagy fast, keep cucumber for your eating window and drink cucumber water instead.
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