TDEE for Intermittent Fasting: How to Set Your Calorie Window
Intermittent fasting (IF) — whether 16:8, 5:2, or OMAD — is a timing strategy, not a calorie-free pass. Your TDEE determines how many calories you need regardless of the window. During a 16:8 protocol, you consume all your daily calories in 8 hours. Knowing your TDEE means you can plan appropriately dense, satisfying meals rather than guessing — or accidentally overeating.
Intermittent fasting doesn't change how many calories you need, it changes when you eat them. The most popular approach, 16:8, means eating within an 8 hour window and fasting for 16 hours. The 5:2 method means eating normally 5 days a week and eating only 500 to 600 calories on 2 non consecutive days. Your TDEE stays the same either way. IF works for weight loss mainly because restricting your eating window naturally reduces total calorie intake. Most people eat fewer calories when they skip breakfast and compress their meals into fewer hours. However, IF isn't magic. If you eat your entire TDEE within an 8 hour window, you won't lose weight. And if you use the eating window to binge, you might even gain weight.
- Your TDEE doesn't change with intermittent fasting. You still need a calorie deficit to lose weight. IF just makes it easier to eat less for some people.
- Start with 14:10 if 16:8 feels too aggressive. Gradually extend your fasting window over two weeks.
- Black coffee, tea, and water are fine during the fasting window. They don't break your fast or spike insulin meaningfully.
- Time your eating window to include your workout. Training in a fasted state is fine for light cardio but can hurt performance during heavy strength training.
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