How major world religions have practiced periodic fasting for centuries.
What the evidence says
- *Greek Orthodox:* Nativity Fast 40 days, Lent 48 days, Assumption 15 days; totaling 180-200 fasting days/year[1]
- *Islamic Ramadan:* 28-30 day fast (no food/drink during daylight hours); health findings mixed due to variations[1]
- *Daniel Fast: 21-day fast prohibiting animal products, refined carbohydrates and additives. The review reports meaningful improvements in blood pressure, blood lipids and oxidative-stress biomarkers, with insulin, HOMA-IR and C-reactive protein lowered to a clinically meaningful extent — and states in the same breath that "only one study to date has examined the health-related effects of a Daniel Fast."*** One study[1]
- *The three traditions are not in the same evidential position, and the review is explicit about it. Greek Orthodox fasting is the strongest: consistently associated with lower body mass, total cholesterol, LDL-C and the LDL-C/HDL-C ratio. Ramadan is mixed — "few definitive conclusions can currently be made… the collective body of research has noted mostly heterogeneous findings", with results on lipids, blood pressure, sodium and fibre each reported both ways. The Daniel Fast rests on one study. This file said "consistent metabolic benefits" across cultures until 2026-09-02; that is the one word the review does not support*[1]