Does pre-workout break a fast?

Pre-workout powders range from zero calories to a scoop full of sugar. The database therefore rates the category grey for all four of the site's own goals. US labels may round a serving under 5 kcal down to 0. The ingredients list tells you more than the calorie line does.

Sugar, dextrose and maltodextrin are carbohydrates at about 4 kcal per gram. They raise blood sugar, so a scoop with any of them ends a blood-sugar or autophagy fast. BCAAs and other amino acids break autophagy, and a 5 g serving comes to about 20 kcal. Sweeteners such as sucralose keep a scoop grey, because their effect on insulin is unresolved. Caffeine with no calories and plain creatine keep a weight-loss fast.

Healthy adults can have up to 400 mg of caffeine a day, with single doses up to 200 mg. Stimulant pre-workouts can cause jitters and a racing heart, so try half a scoop first. A 2023 sleep analysis put the gap for a pre-workout drink at 13 hours before bed.