Can I take caffeine pills instead while fasting?

Yes, plain caffeine has no calories and does not break a fast.

Do BCAAs in pre-workout break a fast?

Yes, amino acids raise insulin and provide calories.

Is fasted training with pre-workout effective?

Many people use a zero-calorie pre-workout before fasted training without breaking their fast.

Does Pre-Workout Break a Fast?

Reviewed by the FastTrack team · Updated June 2026

Short answer: It depends

Pre-workout depends on the formula. A zero-calorie, sugar-free pre-workout will not break a fast, but many contain sugars, BCAAs, or other calories that do, so you have to read the label.

Calories	0-40 kcal (varies)
Breaks a weight-loss fast?	Partial
Breaks ketosis?	Partial
Breaks autophagy?	Yes
Insulin impact	Varies

Why pre-workout depends on the product

Pre-workout supplements vary enormously. Some are just caffeine and stimulants with no calories, which will not break a fast. Others add sugar, maltodextrin, or amino acids such as BCAAs, all of which provide calories and can raise insulin, breaking a fast. The verdict is entirely down to the ingredient list.

How to choose a fasting-safe pre-workout

Look for a product with zero calories, no added sugar, and no amino acids if you want to stay fasted. Pure caffeine, beta-alanine, and citrulline have little to no calorie or insulin impact. If your pre-workout contains BCAAs or carbohydrates, it will break your fast.

How much is safe

One serving of a zero-calorie, amino-free pre-workout before training is fine; check the label, since formulas differ widely.

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Frequently asked questions

Does pre-workout break a fast?: A zero-calorie, sugar-free, amino-free pre-workout does not. One with sugar or BCAAs does.
Can I take caffeine pills instead while fasting?: Yes, plain caffeine has no calories and does not break a fast.
Do BCAAs in pre-workout break a fast?: Yes, amino acids raise insulin and provide calories.
Is fasted training with pre-workout effective?: Many people use a zero-calorie pre-workout before fasted training without breaking their fast.