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Fast every other day. The most aggressive structured fasting protocol.
Last updated: February 21, 2026
2 days/week
Fasting Window
5 days normal
Eating Window
2,000
Est. Weekly Deficit (cal)
~0.57 lbs
Est. Loss per Week
Alternate Day Fasting (ADF) alternates between full fasting days (or severe restriction to 500 calories) and normal eating days in a repeating cycle. It produces the largest weekly calorie deficit of any structured fasting protocol. Research shows ADF is as effective as continuous calorie restriction for weight loss, and some studies show superior improvements in metabolic markers. The challenge is psychological and social: fasting every other day is relentlessly demanding.
On fasting days, eat 0 to 500 calories. On eating days, eat your normal TDEE or slightly below. Strict ADF allows zero calories on fast days, while modified ADF allows up to 500 calories. Most research uses the modified version. The alternating pattern means you fast roughly three to four days per week. Schedule eating days around important social events. Do not compensate for fasting days by overeating on eating days.
| Day | Eating | Fasting |
|---|---|---|
| Monday | Normal eating (TDEE) | None |
| Tuesday | 0 to 500 calories (fast day) | All or most of the day |
| Wednesday | Normal eating (TDEE) | None |
| Thursday | 0 to 500 calories (fast day) | All or most of the day |
| Friday | Normal eating (TDEE) | None |
| Saturday | 0 to 500 calories (fast day) | All or most of the day |
| Sunday | Normal eating (TDEE) | None |
People who have a specific short-term fat loss goal and can commit fully for four to twelve weeks
Those who have maximized results from all other IF protocols
People who can structure their social and work life around an every-other-day fasting schedule
Anyone who cannot afford frequent days of reduced cognitive and physical performance, people with active social or business schedules that include regular meals, and anyone without prior extensive experience with other fasting protocols.
Intermittent fasting controls when you eat. What you eat during the eating window still determines whether you lose fat, maintain muscle, or stall entirely. The most effective approach is scanning your meals with FitCommit as you eat, so you know your daily protein, calorie, and macro totals without logging every ingredient manually. Point your camera at your plate, and the AI identifies the meal and calculates the nutrition in seconds.
Tracking your eating window nutrition takes less than two minutes per day and eliminates the guesswork that causes most IF practitioners to either undereat protein (causing muscle loss) or overeat calories (negating the fast). The combination of a proven fasting schedule and accurate nutrition tracking produces results that neither approach achieves alone.
Track Your Eating Window with FitCommitCalculate your TDEE (Total Daily Energy Expenditure) using a reliable calculator or app. Then eat 10 to 20 percent fewer calories during your eating window to create a calorie deficit. Do not try to eat your entire TDEE in a compressed window. For Alternate Day Fasting, eating 200 to 500 calories below your TDEE on normal days is typically sufficient. FitCommit can calculate your exact TDEE based on lean mass from an AI body scan.
Prioritize protein first: lean meats, fish, eggs, Greek yogurt, cottage cheese, or legumes. Aim for 0.7 to 1.0 grams of protein per pound of bodyweight per day. Fill the rest of your calories with whole foods: vegetables, fruits, whole grains, and healthy fats. Avoid using the eating window as license to eat anything. Alternate Day Fasting creates a calorie reduction primarily through time restriction, but food quality and quantity still determine your results.
Only attempt this after successfully maintaining a less aggressive protocol for at least four to six weeks. Adaptation takes time. During the fasting period, stay hydrated with water, black coffee, or plain tea. Track your eating window with a fasting app or phone timer so you know exactly when to start and stop eating. Most people find it easiest to schedule their fast to overlap with sleep.
Hunger during a fast usually peaks at the times you would normally eat, then fades within 20 to 30 minutes. Drink 500ml of water when hunger hits. Black coffee and plain tea are also effective appetite suppressants and do not break a fast. After one to two weeks, most people find hunger during the fast significantly decreases as their body adapts to the new meal timing.
Scan any meal in seconds. FitCommit's AI identifies your food from a photo and calculates macros instantly. Stop guessing what you ate during your eating window. Free 7-day trial.
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