NASM refers to which organization's code of conduct as a standard of ethical behavior?

The correct answer highlights that NASM adheres to the ethical standards set forth by the American Psychological Association (APA). The APA’s code of conduct outlines principles that promote integrity, professionalism, and respect for the rights and dignity of individuals. This is crucial in the context of behavior change, as professionals in health and fitness fields must ensure they maintain high ethical standards when working with clients to foster a trusting and supportive environment.

Understanding and applying the APA's ethical principles allows NASM professionals to navigate complex interactions with clients, ensuring that they are providing safe, effective, and respectful services. This adherence promotes credibility and accountability, which are vital in fostering long-term behavior change in clients.

Other options, while they may represent organizations involved in wellness or therapy, do not hold the same level of recognition or relevance in setting ethical behavior standards specifically applicable to the practice of behavior change in health and fitness settings as the APA does.