Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It doesn't restrict what you eat, only when you eat. The most popular protocol is 16:8—fasting for 16 hours and eating within an 8-hour window each day.

Yes, but not because of any metabolic magic—it works because most people naturally eat fewer calories when they have a shorter eating window. A 2020 review found IF produces similar weight loss to continuous calorie restriction. The advantage is that many people find it easier to skip breakfast than count calories all day.

Yes—black coffee and plain tea are fine during fasting. They contain negligible calories and don't meaningfully raise insulin levels. Avoid adding milk, cream, sugar, or any caloric additions, as these break the fast. Sparkling water and plain water are also allowed anytime.

Anything with calories breaks a fast. This includes milk, cream, sugar, sweetened drinks, gum (sugary), any food, and most supplements (vitamins with fillers, BCAAs). Black coffee, plain tea, water, and plain sparkling water do not break a fast. Zero-calorie sweeteners are a grey area—they don't spike insulin for most people.

The best eating window is one you can sustain consistently. Most people prefer 12pm-8pm (skipping breakfast) because it aligns with social meals. Earlier windows (8am-4pm) may have slightly better metabolic benefits since they align with daylight hours, but consistency matters more than perfect timing.

For healthy adults, intermittent fasting is generally safe. It's not recommended for: pregnant or breastfeeding women, children and teenagers, people with a history of eating disorders, those with type 1 diabetes, or people who are underweight. If you have any medical conditions, consult your doctor before starting.

Most people feel adapted to IF within 1-2 weeks. The first week is hardest—you may feel hungry or have low energy during fasting hours. By week 2-3, hunger hormones adjust and fasting feels natural. For weight loss results, give it 4-6 weeks of consistent effort before judging effectiveness.