Peptides in this context are functional not dietary. When you eat protein it gets broken down and rebuilt into numerous proteins or used for energy. In this context they are taking a peptide which is just a short amino acid chain but it has very specific functional characteristics. Normally peptides don't make it past the digestive tract which would ruin their specific functional characteristics so, like insulin which is also a peptide, they must be injected to actually work
In the sense that administration of these peptides means that we want to increase their concentration over endogenous levels in order to have some effect
Let's take thymosin beta-4 as an example, it's a protein involved in actin polymerization which is a component of muscle. People use it as a performance enhancer, so theoretically if your ability to recover from high intensity training increases then you can tell it's working. Peptides are no different from other drugs besides the fact that they can be short to long sequences of amino acids
When people read "protein" they think food, however proteins can have physiological effects on the body. Human growth hormone, snake venom and insulin are all proteins, and they do far more than just provide nutrients.
Peptides are just small chain proteins, so the same rules apply.
I don't know man can you measure the effects of any other drug? Why do you think these are somehow different? Did you even read the wikipedia article I linked?
The peptide I mentioned is banned by the world doping agency, but it's probably because it just gives athletes a warm fuzzy feeling right?
At this point your comments seem intentionally disingenuous
There are subjective effects that are much harder to measure though, and these peptide injections fall into that area, as there are numerous environmental and genetic factors one would need to control for.
You say "these" like all peptides are in the category. I'm talking about ones like the one I mentioned earlier. Sure there are some ineffective peptides but there are also ineffective drugs. A peptide banned from sport by the world doping agency is not something with subjective effects
