Plan what to eat before a workout.
The size of a pre-training meal is limited by digestion time, not by appetite. The longer the runway before the session, the more carbohydrate can be cleared from the stomach, which is why the recommendation scales with both body mass and the minutes available. A modest protein dose of roughly 0.25 g per kg is added because it blunts muscle protein breakdown without slowing gastric emptying much, and fluid is prescribed at 5-7 ml per kg two to four hours out.
Pre-session fuelling
Carbohydrate g = weight kg x (minutes ahead / 60) x rate; protein g = weight kg x 0.25; fluid ml = weight kg x ml per kg
These figures are population-average estimates for general planning only and are not medical or dietetic advice. Individual energy and nutrient needs vary widely with body composition, activity, medication and health status. Consult a qualified health professional or registered dietitian before making significant changes to what you eat, and especially if you are pregnant or breastfeeding, are under 18, or have a medical condition or a history of disordered eating.
The calculator scales down automatically — at 20 minutes the carbohydrate figure is small, and it should come from something easily emptied from the stomach such as a sports drink, a banana or a gel rather than a solid meal.
Keep both low. Fat and fiber slow gastric emptying, which is the main cause of the heavy, sloshing feeling in the first 20 minutes of a session, so neither is included in the recommendation.
Fasted low-intensity work is fine and some athletes use it deliberately. But for hard or long sessions, pre-session carbohydrate reliably improves the quality of the work performed, which is what drives the adaptation.