Taper week nutrition is where many otherwise well-prepared marathon runners make their most costly dietary mistakes — either eating too little (feeling guilty about reduced training) or experimenting with new foods at precisely the wrong time. The nutrition goal for the 7 days before a marathon is straightforward: arrive at the start line with maximum muscle glycogen, optimal hydration, and a gut that is calm and predictable.
Studies on carbohydrate loading consistently show that athletes who follow structured pre-race loading strategies have 2–4% faster race times than matched athletes who maintain normal training nutrition. Over a 4-hour marathon, this is 5–9 minutes of free performance.
What Happens Physiologically During Taper
As training volume drops 30–50% in the final 2 weeks, your body undergoes predictable changes: glycogen storage capacity increases (muscles become more efficient at storing glycogen when deprived of training stimulus), inflammatory markers from training load decrease, and muscles undergo micro-repair. The paradox of taper is that many athletes feel worse — heavier, sluggish, and more fatigued — as these adaptations occur. This is normal and does not reflect a loss of fitness. Do not increase training or diet in response to taper "symptoms."
Carbohydrate Loading: The Science
The traditional 7-day carbohydrate loading protocol (which involved a glycogen depletion phase) has been replaced in sports science with a more practical 2–3 day modified loading approach. The modern evidence-supported protocol:
- Days 7–4 before race: Maintain normal, balanced nutrition. No dramatic changes. Slightly increase carbohydrate proportion if it was below 55% of calories during heavy training.
- Days 3–2 before race: Increase carbohydrate intake to 8–12g per kilogram of body weight per day. For a 70kg runner, this is 560–840g of carbohydrates daily — roughly double normal intake. Reduce fat and protein slightly to compensate for volume. Focus on white rice, pasta, bread, banana, and sports drinks.
- Day before race: Continue moderate carbohydrate loading (7–8g/kg/day). Reduce food volume to ease digestion. Eat your last large meal at lunch, with a smaller carbohydrate-rich dinner.
Weight gain of 0.5–2kg during carbohydrate loading is expected and beneficial — each gram of stored glycogen binds approximately 3g of water. This water is available during the race and contributes to hydration status.
How Much to Eat During Taper Week
Many athletes undereat during taper because they feel guilty about reduced activity. This is counterproductive. Your total caloric needs drop by only 10–20% during a 30–50% volume reduction (daily metabolic expenditure, sleep, and daily life remain constant). During carbohydrate loading days, total caloric intake may actually exceed your heavy training calories — this is correct. Maintain caloric intake and adjust macronutrient balance toward carbohydrates.
Foods to Avoid in the Final 72 Hours
- High-fibre foods: Raw vegetables, legumes, wholegrain cereals. These slow gastric transit and increase GI distress risk on race morning.
- High-fat meals: Fatty cuts of meat, fried food, heavy cream sauces. Fat slows carbohydrate digestion and absorption.
- Novel foods: Any food you have not eaten regularly. This is not the time to discover a new restaurant or try an unusual dish.
- Alcohol: Impairs glycogen synthesis, disrupts sleep, and acts as a diuretic — all catastrophic during the final 72 hours of race prep.
- Gas-producing vegetables: Broccoli, cauliflower, cabbage, onion. These cause bloating and GI distress during racing.
Hydration Strategy During Taper
Begin active hydration focus from 3 days out. Target pale yellow urine throughout the day — not clear (overhydration) and not dark yellow (underhydration). Drink 2.5–3L of fluid daily in the 48 hours before race start. Include electrolytes: 300–500mg of sodium per litre helps retain fluid and prevents the pre-race over-hydration that leads to hyponatremia. On race morning, drink 400–600ml of sports drink or water with electrolytes in the 2–3 hours before start time. Stop drinking 30–45 minutes before the gun to allow bladder emptying. Use the Race Day Nutrition Planner to calculate your taper-week carbohydrate targets by body weight and set your pre-race hydration schedule. NorthLine electrolyte drinks are a convenient way to maintain sodium intake during the carbohydrate loading phase without relying on high-sodium processed foods.