Macro Calculator for Intermittent Fasting
Macros for 16:8 intermittent fasting: how to distribute protein, carbs and fat in your eating window.
Do macros change with intermittent fasting?
Intermittent fasting (IF) does not change TDEE or total macronutrient needs — it only compresses the time window in which they are consumed. The 16:8 protocol (16-hour fast, 8-hour eating window) is the most studied: evidence shows similar fat loss and body composition results compared to 3 spread meals when total calories are equal [¹]. However, compressing all protein intake into 2–3 meals requires special attention: to maximise muscle protein synthesis, each meal should provide at least 0.3–0.4 g of protein per kg of bodyweight (30–40 g for most adults) [²].
How to use this calculator
Calculate your total macros normally (IF does not change them). Then distribute intake across your eating window (8h for 16:8, 6h for 18:6, etc.). Prioritise a high-protein first meal when breaking the fast to activate protein synthesis after the catabolic period. Avoid compensating the fast with caloric excess in the window.
Intermittent fasting protocols and macro distribution
| Protocol | Eating window | No. of meals | Protein per meal (70 kg) |
|---|---|---|---|
| 16:8 | 8 hours | 2–3 | 40–50 g per meal |
| 18:6 | 6 hours | 2 | 50–60 g per meal |
| 20:4 (Warrior) | 4 hours | 1–2 | 60–80 g per meal |
| 5:2 (2 days <500 kcal) | Normal 5 days | 3 normal days | Normal on non-fasting days |
FAQ
1Does intermittent fasting burn more fat than a regular diet?
Not independently. Studies that equalise total calorie intake show no significant advantage of IF over conventional distribution for fat loss [¹]. IF's advantage for many people is behavioural: it simplifies the diet and reduces the number of food decisions.
2Can I gain muscle on intermittent fasting?
Yes, though with slight disadvantages compared to spreading protein across more meals. With 16:8 and sufficient protein (1.8–2.2 g/kg/day) in 2–3 meals it is entirely possible [²]. Longer protocols (20:4) may compromise muscle synthesis if protein per meal is not carefully managed.
3Does coffee with milk break the fast?
A small dash of milk (20–30 kcal) probably does not significantly interrupt the metabolic fasting state. However, black coffee or tea are the safest options. Full-fat lattes or drinks with >50 kcal can interrupt autophagy [³].
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