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Eat normally five days a week. Restrict to 500 calories on two non-consecutive days.
Last updated: February 21, 2026
2 days/week
Fasting Window
5 days normal
Eating Window
1,100
Est. Weekly Deficit (cal)
~0.31 lbs
Est. Loss per Week
The 5:2 protocol involves eating normally for five days a week and severely restricting calories (to 500 to 600 calories for women, 600 calories for men) on two non-consecutive days. It was popularized by Dr. Michael Mosley and is one of the most studied forms of modified fasting. The advantage over daily fasting protocols is that you only need to manage hunger two days per week, making long-term adherence easier for many people.
Choose two non-consecutive fasting days each week, such as Monday and Thursday. On fasting days, limit intake to 500 to 600 calories. Spread them across one or two small meals: a protein-rich breakfast and a light dinner work well. On the five normal days, eat your regular TDEE-appropriate diet. Do not intentionally overeat on normal days to compensate. The weekly calorie reduction comes entirely from the two fasting days.
| Day | Eating | Fasting |
|---|---|---|
| Monday | 500 calories (fasting day) | Rest of the day |
| Tuesday | Normal eating (TDEE) | None |
| Wednesday | Normal eating (TDEE) | None |
| Thursday | 500 calories (fasting day) | Rest of the day |
| Friday | Normal eating (TDEE) | None |
| Saturday | Normal eating (TDEE) | None |
| Sunday | Normal eating (TDEE) | None |
People who prefer a weekly rhythm over daily eating windows
Anyone who finds daily fasting too socially restrictive
People who can tolerate intense hunger two days per week in exchange for five completely free days
People with diabetes or blood sugar regulation issues, as 500-calorie days can cause dangerous blood glucose drops, particularly in combination with diabetes medication.
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 FitCommitMost people see a drop of two to four pounds in the first week, almost all of which is water weight and glycogen depletion. True fat loss begins in week two. At the typical calorie reduction from 5:2 Diet (roughly 1,100 calories per week deficit), expect 0.5 to 1.0 lb of fat loss per week after the initial water weight phase. Visible body composition changes typically appear after four to six weeks of consistent adherence.
5:2 Diet is not suitable for pregnant or breastfeeding women, people with a history of eating disorders, those with Type 1 diabetes or insulin-dependent Type 2 diabetes, or anyone under 18. People on blood pressure or blood sugar medications should consult their doctor before starting any fasting protocol, as medication timing may need to be adjusted. If you experience persistent dizziness, extreme fatigue, or heart palpitations, stop the protocol and speak with a healthcare professional.
Calculate 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 5:2 Diet, 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. 5:2 Diet creates a calorie reduction primarily through time restriction, but food quality and quantity still determine your results.
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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