Can you drink coffee while fasting? What black coffee really does to a fast
Dr. Susan Carter, MD: Endocrinologist & Longevity Expert
Nov 30, 2025 · 10 min read
Black coffee does not break a metabolic fast for most men because an 8 ounce cup has about 3 calories and is unlikely to trigger a meaningful insulin response. The real risk comes from what you add to it, plus how caffeine affects hunger, blood sugar, cortisol, and your gut when your stomach is empty. ...