Does collagen break a fast?

Why a scoop counts

Protein has 4 calories a gram ³, so a scoop of 10 to 20 g, the usual size, brings roughly 35 to 70 calories, nearly all of it protein. That's not much, but with protein the kind matters more than the number. In a study of 38 everyday foods, protein foods released much more insulin than their effect on blood sugar would suggest ¹. In a Swedish study, whey released 90% more insulin than white bread ².

Collagen hasn't been tested in the same way, but it's made of the same building blocks, amino acids, and the app's guide puts it with protein shakes and amino acid drinks: all of them belong in your eating window.

Collagen isn't a protein shake

If you use collagen to protect muscle while you fast, know its limits. Protein helps you keep muscle while you lose fat, and it's easy to fall short in a shorter eating window. Gains from strength training level off at about 1.6 g of protein per kilo of body weight a day ⁴. But not all proteins work equally well.

So count collagen as an extra, not as your main protein. Build meals around eggs, fish, meat, dairy, legumes or tofu, and see our guide to protein and muscle.

When to take it

MYTH

Collagen peptides are so small they don't count as protein.

FACT

Peptides are protein broken into shorter pieces. That may make them easier to dissolve and absorb, but they still bring amino acids and calories.

The same goes for bone broth, which is rich in collagen, and for amino acid and BCAA drinks: they're protein, so they end a fast.

Collagen coffee creamers

Collagen creamers sold for coffee often add oil, sugar or milk powder on top of the protein. Read the label: if a product has calories from fat or sugar as well as protein, it's food, and it belongs with your first meal. For a coffee that keeps your fast, drink it black, or with a small splash of milk.

Sources

1. Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997;66(5):1264-76. doi.org/10.1093/ajcn/66.5.1264
2. Nilsson M, Stenberg M, Frid AH, et al. Glycemia and insulinemia in healthy subjects after lactose-equivalent meals of milk and other food proteins: the role of plasma amino acids and incretins. Am J Clin Nutr. 2004;80(5):1246-53. doi.org/10.1093/ajcn/80.5.1246
3. Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex XIV: conversion factors for the calculation of energy. www.legislation.gov.uk/eur/2011/1169/annex/XIV
4. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. doi.org/10.1136/bjsports-2017-097608
5. Oikawa SY, Kamal MJ, Webb EK, et al. Whey protein but not collagen peptides stimulate acute and longer-term muscle protein synthesis with and without resistance exercise in healthy older women: a randomized controlled trial. Am J Clin Nutr. 2020;111(3):708-718. doi.org/10.1093/ajcn/nqz332