Eating Window Builder for Runners
Wake time, bedtime, key session — get a concrete eating window with fuel anchors and honest warnings.
- Default is 14:10 early time-restricted feeding (eTRF) — aligns with circadian cortisol and fuels morning training.
- Window shifted to 09:55–19:55 so your key session falls inside it.
- 09:55Break fast20–40 g protein + complex carbs to stop overnight catabolism.
- 13:15Protein pulse20–40 g protein (leucine ≥ 2.5 g) to keep MPS switched on.
- 17:15Pre-session fuel30–50 g easily digestible carbs (banana, toast, gel).
- 18:00Key sessionThreshold / VO2 intervals
- 19:40Post-session recovery20–40 g protein + carbs within 30–60 min to trigger MPS.
- 19:55Window closesFinal protein pulse — fast begins. No more calories until tomorrow.
How to use this tool
- Set your real wake and sleep times — not your aspirational ones.
- Pick your key session of the day. If you train twice, choose "Double day".
- Set your goal and, optionally, sex (it changes the safety warnings).
- Read the clock dial and the fuel-anchor list. Copy or print the schedule.
The URL updates as you tweak inputs, so you can bookmark or share a specific schedule. Not sure if your plan even needs a fasting window? Ask Pallie.
The rules behind the recommendation
- 14:10 > 16:8 for athletes. 16:8 leaves too little time to hit the 3–4 protein pulses muscle protein synthesis needs. 14:10 is the ceiling for most training plans.
- Early time-restricted feeding (eTRF) beats late. Opening the window near your wake time aligns with morning cortisol and lets you eat before evening digestion starts costing you deep sleep.
- The window must encompass quality sessions. Threshold, VO2, long runs, and strength work need pre-fuel and post-session protein. If your window misses the session, the tool shifts it — or drops to 12:12.
- Never fast longer than 14 hours. Past that, you are in LEA territory and inviting RED-S. The tool refuses to recommend it.
If you're not sure whether intermittent fasting is the right tool for you at all, read the pillar first: Intermittent Fasting for Runners — does it actually work?
Sample schedules
Three worked examples, straight from the research. If your situation looks like one of these, this is roughly what your day should look like.
Morning runner — 14:10, easy Z2 session
| Time | Action | Why |
|---|---|---|
| 06:00 | Wake · break fast | 30–50 g easy carbs to blunt morning cortisol. |
| 06:30 | Zone 2 run (60–75 min) | Sub-threshold; fasted is fine under 90 min. |
| 08:00 | Breakfast (post-session) | 20–40 g protein + complex carbs. Triggers MPS. |
| 12:00 | Lunch | Second protein pulse. |
| 15:30 | Dinner / final fuel | Final protein pulse. Heavier carbs. |
| 16:00 | Window closes | 14 h fast begins |
Evening runner — 14:10, threshold intervals
| Time | Action | Why |
|---|---|---|
| 06:00 | Wake · fast continues | Coffee / water only. |
| 10:00 | Break fast | First protein pulse + foundational carbs. |
| 14:00 | Lunch | Loading glycogen for the evening session. |
| 17:00 | Pre-session snack | 30–50 g easy carbs to top off liver glycogen. |
| 18:00 | Threshold intervals | Fully fed quality work needs glucose. |
| 19:30 | Dinner (post-session) | 20–40 g protein + carbs for recovery & glycogen. |
| 20:00 | Window closes | 14 h fast begins |
Double day — 12:12, AM swim + PM run
| Time | Action | Why |
|---|---|---|
| 06:30 | Morning session (easy swim) | Zone 1; fasted OK for the low-intensity half. |
| 08:00 | Break fast | Immediate 20–40 g protein to halt overnight catabolism. |
| 13:00 | Lunch | High-carb meal to refuel before evening effort. |
| 16:00 | Pre-session snack | Top-off carbs. |
| 16:30 | Evening run (quality) | Fully fed |
| 17:30 | Dinner (post-session) | Final recovery meal of the day. |
| 18:00 | Window closes | 12 h fast begins |
Pre-session fuel minimums
- Easy < 60 min: fasted is fine. Optional espresso.
- Zone 2, 60–90 min: 20–30 g carbs 30 min prior if you can stomach it.
- Threshold / VO2 / intervals: 30–50 g easy carbs 30–60 min prior. Non-negotiable.
- Long run > 90 min: 50 g carbs beforehand + 60–90 g/h intra.
- Strength (heavy compound): eat 1–2 h prior. Training fasted kills power output.
Post-session recovery window
The muscle-protein-synthesis switch is time-sensitive. You have roughly 30–60 minutes after a hard session where a 20–40 g dose of high-quality protein does disproportionate work — it hits the leucine threshold (≥2.5 g), switches on the mTOR pathway, and keeps MPS elevated for 2–3 hours before decaying.
- 20–40 g whole protein (≈3–6 eggs, 150 g chicken, 1 scoop whey).
- Complex carbs alongside, to refill muscle glycogen.
- Water + sodium if the session was over 60 min or hot.
- Then keep pulsing protein every 3–4 hours until your window closes.
When NOT to use this tool
Time-restricted eating is a tool, not a moral position. There are clear cases where the right answer is just to eat normally:
- Currently in RED-S recovery. You need to eat more, not restrict when you eat. Work with a sports dietitian.
- Pregnancy or breastfeeding.Energy demands are non-negotiable. Don't fast.
- History of disordered eating. Restriction rules, even well-intentioned ones, can be a trigger.
- Masters athlete with bone-density concerns. Chronic LEA accelerates bone loss — the last thing you want.
- Under-18. Full stop.
- Peak training block or race taper. Fuel for the work required; save metabolic experiments for base phase.
Eating Window Builder FAQ
What's the difference between 12:12, 14:10, and 16:8?
The numbers are hours of fasting and hours of eating. 16:8 (16 h fast, 8 h eating) is the most aggressive and the one we don't recommend for runners — it crams all protein and training fuel into 8 hours. 14:10 is the sweet spot for most athletes, long enough for metabolic benefit, short enough to still hit 3–4 protein pulses. 12:12 is the conservative baseline we fall back to for double days, female performance goals, and anyone in a hard training block.
Should my eating window include my workout?
For any quality session — threshold, VO2, long run, strength — yes. You need carbs before it (30–50 g, 30–60 min prior) and protein plus carbs within 30–60 min after it. Easy Zone 1/2 runs under 60 minutes are the only sessions safe to do fasted, and only if you top up immediately on return.
Can I drink coffee during my fast?
Yes. Black coffee, plain tea, and water don't break a fast. Caffeine before a fasted easy run actually lowers perceived exertion. Skip anything with milk, cream, sugar, or sweeteners — those ping insulin and end the fasted state.
I train twice a day — what window should I use?
12:12, not 14:10. Your eating window has to cover both sessions plus a recovery meal after each one. The morning session is the one to keep easy and can be fasted; the evening session is the quality/strength work and must be fully fed. The tool defaults to 12:12 when you select "Double day".
Does this tool account for female physiology?
Partly. If you set sex to female and goal to performance, we cap the fast at 12:12 and flag cycle-phase risk. In your luteal phase (roughly days 15–28) your body relies more on fat and tolerates fasted quality work badly — shorten to 12 h or skip fasting that week. The tool can't know your cycle, so the warning is blanket. When in doubt, fuel.
What if I work shifts?
Anchor the window to your wake time, not the clock. If you wake at 14:00 and sleep at 06:00, a 14:10 window running 14:00–24:00 is mathematically equivalent to the morning version. What you can't do is run a 16-h fast across a training session — the biology doesn't care what your calendar says.
How long until I see results?
Body-composition changes from time-restricted eating typically show up in 4–8 weeks if you're in a mild caloric deficit. Performance will not improve from fasting alone — the best you can hope for is to maintain current fitness while losing a bit of fat. If performance drops in the first 2–3 weeks, the window is wrong for you.
Is this safe if I'm in a calorie deficit?
Only if the deficit is mild (≤300 kcal/day) and you're a healthy, well-fuelled athlete to start with. Combining fasting + a steep deficit + endurance training is the classic road to RED-S: low energy availability, hormonal disruption, bone loss, sports anemia. If you've got fatigue, skipped periods, frequent colds, or plateauing HRV — stop fasting and fuel up.