Does Collagen Break a Fast?

Reviewed by the FastTrack team · Updated June 2026
Short answer: Yes

Collagen breaks a fast. Collagen peptides are protein, which provides calories and raises insulin, so a scoop will end a fast and stop autophagy.

Calories~35-70 kcal per scoop
Breaks a weight-loss fast?Yes
Breaks ketosis?No
Breaks autophagy?Yes
Insulin impactYes

Why collagen breaks a fast

Collagen is protein, and protein both provides calories and triggers an insulin response. A typical scoop has 35 to 70 calories and around 10 to 20 grams of protein, which is enough to leave the fasted state and switch off autophagy through the mTOR pathway. It does not raise blood sugar like carbohydrate, but it still breaks a fast.

It does not break ketosis, but it breaks the fast

Because collagen has no carbohydrate, it will not knock you out of ketosis, which is why some keto dieters use it. But ketosis and fasting are not the same thing: collagen still provides protein calories and stimulates insulin, so it breaks a fast. Save it for your eating window.

How much is safe

There is no fasting-safe amount of collagen, since even a small scoop provides protein calories. Take it during your eating window.

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Frequently asked questions

Does collagen break a fast?
Yes, it is protein with calories and an insulin response.
Does collagen break ketosis?
No, it has no carbohydrate, but it still breaks a fast.
Can I put collagen in my fasting coffee?
It will break your fast; add it during your eating window instead.
How many calories are in a scoop of collagen?
Usually about 35 to 70, all from protein.

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