Intermittent Fasting Calculator

IF alone does not cause more muscle loss than traditional dieting when protein intake is adequate. Several studies (Moro et al. 2016) show trained individuals preserved more muscle while losing fat comparing IF vs. normal eating at matched calories and protein. The key is hitting your daily protein target within your eating window, typically 1.6–2.2 g/kg body weight.

Zero-calorie drinks are generally accepted: water, black coffee, and plain tea do not meaningfully break a fast. Avoid adding milk, cream, sugar, or sweeteners that contain calories. Some IF practitioners allow small amounts of MCT oil or BCAAs, though purists consider anything with calories as breaking the fast. For autophagy benefits, strict zero-calorie fasting is preferred.

Both fasted and fed training work. Fasted cardio may slightly increase fat oxidation during the session, but the total daily effect on fat loss is minimal. For strength training, training at or near the start of your eating window — so you can eat protein shortly after — may help with recovery. If morning training during a fast is your only option, it works fine for most people's performance.

IF is safe for most healthy adults. It may not be appropriate for people with diabetes (especially type 1), those with a history of eating disorders, or individuals who are pregnant or breastfeeding. Some people experience headaches, fatigue, or irritability when starting — these typically resolve within 1–2 weeks as the body adapts. Always consult your doctor before making major dietary changes.