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Gluc:fruc ratio

What it is. The gluc:fruc ratio is the balance of glucose to fructose in an athlete’s carbohydrate. The two sugars are absorbed across the gut by different transporters, so a blend draws on both pathways rather than saturating one. This is why blended carbohydrate is tolerated better at high intakes than the same grams of glucose alone. What the dial does in Saturday. It sets the blend Saturday builds toward. Every carb source carries a known glucose fraction: table sugar is half glucose and half fructose, maltodextrin and dextrose are effectively all glucose, fructose is none. Saturday takes the carbohydrate-weighted average across everything in the recipe and composes the mix, or suggests a swap, to land on the ratio you asked for. What it does not do. The ratio does not set how many grams per hour the athlete is prescribed. That number comes from their profile: the carbohydrate intake they have reported handling, their satiety setting, and the session’s demands. Changing the ratio changes what the carbohydrate is made of, not how much of it there is. If an athlete needs a higher carbohydrate target, that is a profile change, not a ratio change. When to change it. When an athlete is pushing high carbohydrate targets on long or hard sessions, or when they report stomach trouble at intakes that have not previously bothered them. The question it answers. “Why can’t I just drink more of one sugar?”

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What you do as a coach

  • Read the athlete’s current ratio by opening them from your roster.
  • Pick from the offered set. The portal offers a fixed set of ratios, from pure glucose up to equal parts glucose and fructose. See The Setup for how to change one.
  • Pair it with the fill. A branded product may already carry a tuned blend, while a kitchen mix lets you hit a ratio from staples. See Eco-mode vs products.
An unknown blend is left out rather than guessed. When a product’s glucose-to-fructose split is not known, Saturday excludes it from the ratio and reports those grams separately, instead of assuming an even split. A ratio you see is computed from sources whose composition is known.

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See also