The 12-Week Race Nutrition Timeline: What to Focus On Each Phase

Your race nutrition plan has a deadline — and it is not race morning

Most runners start thinking about race nutrition far too late. A week before the marathon, the panic searches begin: "how many gels should I take," "what do I eat the morning of," "should I carb load." By then, the window to build a plan you trust has already closed.

Elite athletes treat nutrition as a training variable with its own periodisation. Sabastian Sawe spent 12 months refining the fueling protocol behind his 1:59 marathon. You do not need 12 months. But you do need 12 weeks.

This timeline breaks your race nutrition prep into four phases. Each phase has a specific focus, specific actions, and a clear goal. Follow it from 12 weeks out and you will arrive at the start line with a fueling plan you have tested, adjusted, and trust completely.

Phase 1: Baseline and assessment (weeks 12–10)

Goal: Understand where you are starting from.

Before you change anything, you need to know your current state. This phase is about collecting the data that will inform every decision over the next three months.

What to do

Estimate your sweat rate. Weigh yourself before and after a 60-minute run at your easy pace. The difference in grams, plus whatever fluid you drank during the run, equals your approximate fluid loss per hour. Do this in conditions similar to your expected race-day weather. If your race is in October, test in the warmest conditions you can find — your sweat rate in summer training will be higher than on a cool race morning, and it is better to plan for the higher end.

Audit your current fueling. On your next long run, pay attention to what you eat and drink, when you eat and drink it, and how your stomach responds. Most runners discover they are either under-fueling (skipping gels because they feel fine until they suddenly do not) or fueling inconsistently (nothing for 90 minutes, then three gels in 20 minutes).

Calculate your carb target. The current evidence-based recommendation is 60–90 grams of carbohydrates per hour for marathon-distance events. Where you fall in that range depends on your body weight, pace, and gut tolerance. A 60kg runner finishing in 3:30 has different needs than an 85kg runner finishing in 4:45.

As a starting point: aim for 60g/hour if you have never practised fueling during runs. Aim for 70–80g/hour if you have some experience with gels. Only target 90g+ if you have a tested, progressive gut-training history.

Pick your products. Choose the gels, chews, or drink mixes you plan to race with. This is not the time for variety — you need consistency for the testing phase ahead. Consider carb content per serving, whether the product needs water, flavour preferences during exercise, and caffeine content (save caffeinated gels for race day or key sessions only).

What Sweatr does at this stage

Sweatr pulls your training data from your Apple Watch, Garmin, or Strava and calculates your estimated sweat rate, calorie burn, and carb needs based on your actual activity data — not population averages. It gives you your baseline numbers without the manual weighing and spreadsheet work.

Phase 2: Gut training and product testing (weeks 9–6)

Goal: Train your gut to tolerate your target carb intake at race effort.

This is the phase most runners skip entirely, and the reason most race-day stomach problems happen. Your gut is a trainable organ. It adapts to the demands you place on it — but adaptation takes weeks, not days.

What to do

Start gut training on long runs. Begin taking your chosen fuel during every long run from week 9 onward. Do not wait for the "big" long runs. Your body needs repeated exposure to absorbing carbohydrates during exercise.

Week 9–8: Baseline tolerance. Take one gel or serving at 40–45 minutes into your long run, then one more every 40 minutes. This is approximately 40–50g carbs per hour. Note any GI symptoms: bloating, nausea, urgency, cramping.

Week 7–6: Progressive increase. Increase frequency to every 30 minutes, bringing you closer to 60–70g carbs per hour. If you tolerate this well, increase to every 25 minutes on your longest run during this block. If you experience GI distress, hold at the previous level for another week before increasing.

Match your hydration. Always take gels with water, never with a sports drink (the combined sugar concentration can overwhelm your gut). Aim for 150–200ml of water per gel. If you are using a carbohydrate drink mix instead of gels, do not add extra gels on top without reducing the drink concentration.

Test your exact race-day products. Do not train with Brand A and race with Brand B. Different gels have different osmolalities, different carb sources (glucose, fructose, maltodextrin), and different textures. Your gut adapts to the specific product, not just the carb load.

The signal that gut training is working

You should notice that the same carb intake that caused mild discomfort in week 9 feels normal by week 6. If a particular product consistently causes problems despite progressive exposure, switch products now — not in week 2.

Phase 3: Race simulation and plan lock-in (weeks 5–3)

Goal: Run your final long runs with your complete race-day nutrition plan.

By week 5, you should have a clear fueling plan: which products, how much, how often, with how much fluid. The goal of this phase is to rehearse the entire protocol under conditions as close to race day as possible.

What to do

Run at least two long runs with your full plan. These are your dress rehearsals. Use the exact products, exact timing, and exact fluid intake you plan to use on race day. Carry your fuel the way you will carry it in the race (belt, pockets, or relying on aid stations).

Simulate race-day timing. If your race starts at 7am, run your dress rehearsal long runs at 7am. Eat the same pre-run breakfast at the same time. This trains your circadian digestion as well as your gut tolerance.

Test your pre-run meal. The morning-of breakfast is part of the plan. A common approach: 2–3 hours before the start, eat 1–2g of carbohydrate per kilogram of body weight. For a 70kg runner, that is 70–140g of carbs — roughly a bowl of porridge with a banana and honey, or two slices of white toast with jam and a sports drink. Test this on your long run mornings.

Plan for aid station logistics. If you are relying on on-course nutrition (water, sports drink), rehearse grabbing cups while running. If you are carrying everything, confirm your carrying setup is comfortable for the full distance. Small logistics failures on race day — fumbling a gel, missing a water station — cascade into fueling gaps that compound over hours.

Finalise your race-day hydration volume. Based on your sweat rate testing and the forecast for race day, set your target fluid intake per hour. For most marathon runners, this falls between 400ml and 800ml per hour. Adjust upward for heat (above 20C) and downward for cool, overcast conditions.

Lock the plan

After your final dress rehearsal long run (typically 3 weeks before race day), your plan is locked. Write it down: what you eat for breakfast, when you take your first gel, how often you fuel, how much you drink, when you take caffeine (if at all), and what you do if your stomach objects. No more changes after this point.

Phase 4: Taper nutrition and race week (weeks 2–0)

Goal: Arrive at the start line fueled, hydrated, and confident.

The taper is not a time to experiment. It is a time to maintain your nutrition habits while your training volume drops.

Weeks 2–1: Maintain, do not over-eat

A common taper mistake is eating significantly more because you are anxious about "topping up" glycogen. Your training load has decreased, so your calorie needs have decreased. Eat normally. Your glycogen stores will replenish naturally as training volume drops.

Keep your daily hydration consistent. Do not suddenly start drinking three litres of water a day if you normally drink two. Over-hydrating in the days before a race dilutes sodium levels and can leave you feeling bloated and sluggish.

Race week: Carb loading done right

Carb loading is real and evidence-based, but it does not mean eating pasta until you feel ill. The goal is to maximise muscle glycogen stores in the 48–72 hours before the race.

The practical approach: Increase carbohydrate intake to 8–12g per kilogram of body weight per day for the final 2–3 days. For a 70kg runner, that is 560–840g of carbs per day. Focus on familiar, easily digestible carbohydrates: white rice, white bread, pasta, potatoes, bagels, sports drinks, fruit juice. Reduce fibre, fat, and protein slightly to make room for the extra carbs without increasing total food volume too much.

Sodium loading. If you are a salty sweater or racing in warm conditions, consider increasing sodium intake in the 24–48 hours before the race. Adding salt to meals or sipping an electrolyte drink throughout the day can pre-load your sodium stores. This is not about drinking litres of salt water — it is about slightly elevating your baseline so you start the race with a buffer.

Race morning: The 4-hour countdown

4 hours before start: Wake up. Sip water or electrolyte drink.

3 hours before start: Eat your tested pre-race breakfast. This should be familiar — the same meal you ate before your dress rehearsal long runs.

2 hours before start: Finish your main fluid intake. Small sips only from here.

1 hour before start: Optional top-up gel or small carb snack (a banana, a few sweets). This is preference-based. Some runners feel better with a small boost; others prefer an empty stomach.

30 minutes before start: Final sip of water or electrolyte drink. Nothing new, nothing unfamiliar.

Start line: Your first gel should come at 30–45 minutes into the race, not at the start. Your glycogen stores are full — you do not need immediate fueling. Starting too early wastes gut capacity.

The cost of winging it

The difference between a good race and a bad race is rarely fitness. Athletes who train for months and execute their running plan perfectly still blow up because their nutrition plan was improvised.

A 2023 study of recreational marathon runners found that 47% reported GI symptoms during the race, and the most common cause was consuming unfamiliar foods or drinks on race day. Separately, research on marathon finishers shows that athletes who practise their fueling strategy during training are significantly less likely to experience GI distress and report higher satisfaction with their race performance.

The pattern is consistent: athletes who plan, test, and lock in their nutrition outperform athletes who wing it, even when their fitness is identical.

Build the plan your data supports

This 12-week timeline gives you the structure. But the specific numbers — your carb target, your sweat rate, your fluid needs, your adjustment for race-day weather — depend on your data.

Sweatr pulls your training history from your Apple Watch, Garmin, or Strava and builds a personalised race-day nutrition plan calibrated to your body weight, training load, sweat rate, and target pace. It tells you exactly what to eat, when to eat it, and how much to drink — and it adjusts the plan if conditions change.

You have spent months training your legs. Spend 12 weeks training your nutrition too.