Pre-race fueling and carb loading — 1-day, 3-day, 6-day protocols
The classic Sherman/Costill depletion-then-loading protocol is dead. Modern marathon loading is gentler, faster and more evidence-based. Here is what the data actually supports.
The 1981 Sherman and Costill depletion-then-loading protocol (IJSM) — deplete glycogen with a hard run 7 days out, eat low-carb for 3 days, then switch to high-carb for 3 days — has been superseded by gentler, equally effective approaches.
The modern standard for a marathon is the 6-day modified loading protocol (Burke and colleagues): progressive carbohydrate increase that mirrors the training taper, culminating in 10–12 g/kg/day during the 36–48 hours before the race. For a 70 kg runner, that is 700–840 g of carbohydrate per day — which sounds like a lot until you realise a single 200 g plate of pasta delivers ~140 g, a 150 g bread roll another 80 g, and a sports drink bottle 60 g.
The fastest evidence-based alternative is Fairchild et al.'s 1-day rapid load (MSSE, 2002): 10 g/kg/day of carbohydrate for a single day combined with minimal exercise super-compensates muscle glycogen in trained athletes. It is especially useful for runners who find the 3-day plan uncomfortable or who get GI symptoms from the volume of food required over multiple days.
Race-morning fuelling. 3–4 hours before the gun: 1.5–4 g/kg of low-to-moderate-glycemic-index carbohydrate (oatmeal, banana, honey, a bagel, coffee). The earlier the meal, the larger it can be. Optional 30 g top-up 10–15 min before the start (gel, sports drink) — there is no meaningful rebound hypoglycaemia risk in warmed-up runners (Jeukendrup & Killer, Annals of Nutrition and Metabolism, 2010), despite the persistent myth.
The "fasted breakfast" debate resolves in favour of fed for races >90 minutes. For 5K, where glycogen is not limiting and GI comfort matters more, fasted is acceptable. For half-marathon and up, eat.
FODMAP reduction in the 24–48 hours before the race (Lis et al., MSSE, 2018) is a legitimate intervention for runners prone to GI distress — temporarily reduce wheat, onions, garlic, legumes, apples, stone fruit, sugar alcohols. This is a pre-race tool, not a long-term dietary pattern.
The single most important principle across all of this: nothing new on race day. Every item of the pre-race meal and every gel on course must have been rehearsed on at least two long runs.