Your Complete Fasting Calculator

Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. It doesn't specify which foods to eat but rather when you should eat them. Popular methods include the 16/8 method (16 hours of fasting, 8 hours of eating), the 5:2 diet (eating normally 5 days of the week, restricting calories on 2 days), and alternate-day fasting.

No, fasting is not recommended for everyone. People who should avoid fasting include pregnant or breastfeeding women, children and adolescents under 18, people with a history of eating disorders, those who are underweight, and individuals with certain medical conditions such as diabetes (unless specifically supervised by a doctor). Always consult with a healthcare provider before starting any fasting regimen.

During fasting periods, you can generally consume water, black coffee, and unsweetened tea without breaking your fast. These beverages contain zero calories and won't trigger an insulin response. Some fasting protocols may allow small amounts of cream in coffee or bone broth, while others are more strict. Avoid beverages with artificial sweeteners, as some may trigger an insulin response despite having zero calories.

Weight loss varies greatly depending on your starting weight, fasting protocol, diet quality during eating windows, and other factors like activity level. Many people lose between 0.5-2 pounds per week with intermittent fasting, while more extended fasts may result in faster initial weight loss (though much of this is water weight that returns after the fast). Our various calculators can provide personalized estimates based on your specific metrics and chosen fasting method.

Research suggests that short-term fasting (less than 72 hours) does not significantly slow metabolism. In fact, some studies indicate that fasting for less than 3 days can slightly increase metabolic rate due to the release of norepinephrine. However, extended fasting beyond 3 days or chronic calorie restriction may eventually lead to metabolic adaptation. Intermittent fasting protocols with adequate calorie intake during eating windows typically don't negatively impact metabolic rate in the long term.

Yes, many people successfully exercise while fasting. Low to moderate-intensity activities like walking, yoga, or light cardio are generally well-tolerated during fasting periods. Some people even prefer high-intensity training in a fasted state, as it may enhance fat burning. However, your performance might be affected, especially for high-intensity or long-duration workouts. Listen to your body and consider scheduling intense workouts close to your eating window. If you're new to fasting, start with lighter exercise until your body adapts.

Our fasting calculators use evidence-based formulas to provide personalized estimates and guidance. For example, the Intermittent Fasting Calculator helps you determine your optimal eating and fasting windows based on your chosen protocol. The Weight Loss Fasting Calculator uses your age, gender, weight, height, activity level, and chosen fasting method to estimate potential weight loss over time. Each calculator is designed to give you realistic expectations and practical information to support your fasting journey.

The frequency of extended fasting depends on your experience level, health status, and goals. For beginners, a 24-hour fast once per week may be appropriate. More experienced fasters might do 48-hour fasts once every 2-4 weeks. 72-hour or longer fasts are typically done less frequently, perhaps once every 1-3 months. It's important to allow adequate recovery time between extended fasts and to focus on nutrient-dense foods during eating periods. Always consult with a healthcare provider before attempting regular extended fasting.