Does a spoon of peanut butter break a fast?

Yes, even a tablespoon has about 90 to 100 calories.

Does peanut butter break ketosis?

Larger amounts and added-sugar versions can affect ketosis.

Is peanut butter okay during intermittent fasting?

Yes, during your eating window, not during the fast.

Does Peanut Butter Break a Fast?

Reviewed by the FastTrack team · Updated June 2026

Short answer: Yes

Peanut butter breaks a fast. A spoonful packs around 90 to 100 calories from fat and protein, with some carbohydrate too, which ends a fast and stops autophagy.

Calories	~90-100 kcal per tbsp
Breaks a weight-loss fast?	Yes
Breaks ketosis?	Partial
Breaks autophagy?	Yes
Insulin impact	Yes

Why peanut butter breaks a fast

Peanut butter is calorie-dense food: a single tablespoon has about 90 to 100 calories from a mix of fat, protein, and a few grams of carbohydrate. The protein and carbohydrate raise insulin and the calories end any fast, including a fat-loss fast. It is one of the easiest foods to overeat, which makes it a poor fasting choice.

No fasting-safe spoonful

Because it combines protein, carbohydrate, and a lot of calories, there is no small amount of peanut butter that stays within a fast. Enjoy it in your eating window, where its protein and healthy fats are genuinely useful, but keep it out of your fasting hours.

How much is safe

Even one tablespoon has about 90 to 100 calories; save peanut butter for your eating window.

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Frequently asked questions

Does peanut butter break a fast?: Yes, it is calorie-dense and raises insulin.
Does a spoon of peanut butter break a fast?: Yes, even a tablespoon has about 90 to 100 calories.
Does peanut butter break ketosis?: Larger amounts and added-sugar versions can affect ketosis.
Is peanut butter okay during intermittent fasting?: Yes, during your eating window, not during the fast.