Benefits
Body composition with exercise
In one randomized controlled trial, 97 middle-aged untrained men took 15 grams a day of collagen peptides or placebo for 12 weeks while all of them did the same resistance training. Fat free mass rose 3.42 kg with the peptides versus 1.83 kg with placebo, and fat mass fell 5.28 kg versus 3.39 kg. Because both groups trained, training itself produced most of the change.
Muscle and strength
In that same trial, leg strength rose by 163 N with the peptides versus 100 N with placebo over 12 weeks. A third group took whey protein and landed in between, without being significantly different from either collagen or placebo, so collagen has not been shown to work better than ordinary protein.
Connective-tissue support
Collagen is rich in the amino acids glycine, proline, and hydroxyproline, which the body uses to build connective tissue. The one cited trial did not measure tendons or connective tissue, so this is background chemistry rather than a tested benefit.
Mechanism of action
Amino acid signaling
Collagen peptides deliver amino acids that may add to the muscle building signal of resistance training. This is a proposed explanation, not something the single published trial measured.
Connective-tissue substrate
Collagen provides building blocks for the connective tissue framework that surrounds muscle and transmits force. This comes from basic biology, not from a study of this ingredient.
Clinical trials
Randomized controlled trial of 15 grams a day of specific bioactive collagen peptides over 12 weeks, with every group following the same resistance training programme. The published paper does not name BODYBALANCE, and one author disclosed financial interests related to collagen. (Zdzieblik et al. 2021, International Journal of Environmental Research and Public Health)
97 middle-aged untrained men who completed the study. No women and no trained athletes took part.
Fat free mass rose 3.42 kg with collagen versus 1.83 kg with placebo (p=0.010), and fat mass fell 5.28 kg versus 3.39 kg (p=0.023). Leg strength rose 163 N versus 100 N. A whey protein group fell in between and was not significantly different from either collagen or placebo.