Two widely hyped peptides for fitness are sometimes marketed together and nicknamed the 'Wolverine stack.' Tom Werner/DigitalVision via Getty Images It’s tough to avoid the current hype about the health benefits of injecting peptides. Although these substances – essentially, synthetic bits of protein in solution – have long made the rounds in the fitness world, their popularity has exploded. Social media influencers, podcasters, wellness clinics and online sellers promote peptides as a quick