Carbohydrate loading (carb-loading)
A nutrition strategy for endurance athletes that involves sharply increasing carbohydrate intake before a competition to maximise glycogen stores.
Carbohydrate loading (« carb-loading ») aims to saturate glycogen stores (in muscle and liver) before a prolonged endurance effort (marathon, triathlon, long-distance cycling). The goal: delay glycogen depletion, the infamous « wall », which hits at around 90 minutes of intense effort.
A fresh angle (the strategy has evolved): the classic carb-loading of the 1960s-70s was brutal: a depletion phase (exhausting glycogen through training plus a low-carbohydrate diet for several days) followed by an overload. This « shock » method was gruelling and risky.
Modern protocols are gentler and effective: you simply increase carbohydrate (up to 8-12 g/kg/day) during the 1-3 days before the event, while cutting back on training (tapering). No need for an exhausting depletion phase.
Glycogen water (the scales effect): every gram of glycogen is stored with ~3 g of water. A successful carb-load therefore makes you gain 1-2 kg on the scales, but that is water and glycogen, not fat. Athletes know this; beginners sometimes panic. This water retention is beneficial (hydration, available energy).
Who is it for? (an important nuance): carb-loading only makes sense for efforts of over 90 minutes of continuous exercise. For a weights session, a 30-minute jog or a short match, it is pointless, as normal stores are enough. Loading up on carbohydrate before a short effort just stores it with no benefit.
During long efforts: beyond the initial store, very long efforts (over 2-3 hours) require refuelling with carbohydrate during the effort (30-90 g/h) to maintain blood sugar.
In practice: easily digestible carbohydrate sources (pasta, rice, bread, fruit) in the preceding days, avoiding excess fibre and fat on the day itself (for digestive comfort).