Can I exercise while fasting for 18 hours?

Yes, you can exercise while fasting ( 41 ). Low-intensity cardio (Zone 2) is excellent during the later hours of a fast to target fat oxidation ( 42 ). High-intensity interval training (HIIT) or heavy lifting is also possible, but performance may vary ( 43 ). Listen to your body – if you feel lightheaded, consider shifting your workout to your feeding window or consuming essential amino acids (EAAs) prior to training.

How many calories do I burn if I fast for 18 hours?

Fasting itself doesn’t inherently “burn” extra calories in a significant way compared to eating the same amount of calories spread out. Fasting primarily works by controlling calorie consumption (reducing the opportunity to eat) and optimizing hormones to allow access to fat stores ( 44 ). Any metabolic “boost” from fasting would be minimal compared to the deficit created by simply not eating a third meal.

Can you drink coffee while intermittent fasting?

Yes, black coffee is permitted and often encouraged. It contains negligible calories and doesn’t spike insulin. However, you must avoid adding sugar, milk, cream, or MCT oil, as these contain calories that will break the fasted state.

What can I drink during the 18:6 fasting window?

During the 18-hour fasting period, stick to zero-calorie beverages: plain water, sparkling water, black coffee, and unsweetened tea (green, black, or herbal).