What term is used for individuals who undergo physical changes to align their bodies with their gender identity?

The term that is used for individuals who undergo physical changes to align their bodies with their gender identity is "transsexual." This term specifically refers to individuals who may pursue medical procedures such as hormone therapy or gender-affirming surgeries to bring their physical body into alignment with their deeply-felt sense of their gender identity, often moving from one sex to another.

While "transgender" is a broader term that encompasses anyone whose gender identity does not align with their sex assigned at birth, "transsexual" implies a specific aspect of transitioning that includes physical changes. In contrast, "gender fluid" refers to individuals who may not consistently identify with one gender and can experience shifts in gender identity over time. "Non-binary" describes individuals who do not identify exclusively as male or female, which may or may not include physical changes to their bodies. Thus, "transsexual" is the most accurate term for the context provided in the question regarding physical changes.