I think Personally, I don’t know. However, I am a cis person who has had body dysmorphia. Even when I was unhealthily thin, I perceived myself as disgustingly fat. I genuinely believed that things would be better if I just lost “one more kilo — just one more, and things will all be fine and I’ll start seeing myself as a human deserving of respect rather than just a disgusting lump. Yes, I know I said that 5 kilos ago, but just one more will do it”.

There was a fundamental mismatch between my perceptions and reality. As a small aside, your comment mentioned “body dysphoria”, when I suspect you meant “body dysmorphia” (and “gender dysphoria” is what many trans people experience). I’m not highlighting this to be a persnickety asshole, but because I think the (body) dysmorphia vs (gender) dysphoria contrast is interesting. Whilst my experience was rooted in disproportionately magnified perceptions of flaws, gender dysphoria is rooted in reality: consider someone who is assigned male at birth who later comes out as a trans woman. If she decides to go for medical transition (which typically involves hormones and surgery), these are pretty serious changes that wouldn’t make sense if someone already believed they were a cis woman. Rather, the gender dysphoria that many experience arises from an acute understanding of both the biological reality of their body, and the sociocultural reality of how people tend to perceive that body. (I also want to note, as a biochemist, that the way that our bodies respond to hormones is also part of biological reality. Like, if someone assigned male at birth starts taking estrogen, their body will go “cool, guess we’re making titties now”. Human nature, if it exists as a unified concept at all, is fundamentally fluid, and I wish we spoke about this more)

The key thing in distinguishing between gender dysphoria and body dysmorphia is the proposed treatment. Every kilogram I lost caused me to become more miserable, more caught up in my distorted perceptions, and more physically frail. Even before I had lost an unhealthy amount of weight, it would have been patently clear to an outside observer how bullshit my “just one my kilogram” spiel was. For trans people undergoing medical transition though, it’s a completely different story. Whilst I’m told by multiple friends that first starting HRT does feel like taking the red pill in the matrix, the ongoing reality of it isn’t quite so dramatic. Many of the changes are permanent, but they’re gradual enough that with support and oversight from medical professionals who understand trans people, there is so much opportunity to gauge whether this is the right path for a person. Whilst there are some people who regret transitioning, the regret rate for gender confirmation treatments is stunningly low compared to other cosmetic surgeries (I don’t have the number to hand, sorry). In terms of positive treatment outcomes, there are oodles of evidence that show that medical transition is absurdly beneficial — it’s a strong enough case that even if I didn’t care at all about the wellbeing of trans people, there’s a super strong case for the economic benefits of good access to gender affirming healthcare.

To put it simply, the difference between body dysmorphia and gender dysphoria is evident in how they respond to treatment. The therapy I underwent focussed on unwinding and unlearning the false perceptions of myself. In contrast, conversion therapy is not just an inhumane way to respond to gender dysphoria, but proven to be harmful. On the other side of things, indulging my delusions would have just deepened my spiral, whereas medically supported gender transition is proven to save lives and increase trans people’s wellbeing.

(N.b. I have focussed on medical transition here because that’s the angle that naturally arises from your question. However, not all trans people who experience gender dysphoria necessarily want to medically transition, finding that social transition (living as one’s chosen gender) is enough for them. I feel it important to highlight that many trans people I have known have expressed that they feel there would be far fewer trans people feeling they need to undergo medical transition if the world wasn’t so shitty to people who are gender non conforming. Also notable is that not all trans people experience gender dysphoria, and there are plenty of trans people who actively want to get away from thinking about things in terms of gender dysphoria, because they feel that it promotes an overly medical approach that can be harmful, such as how access to trans healthcare is increasingly being gatekept for bullshit reasons (their bigotry is transparent because in blocking access to trans healthcare, they are actively ignoring a pretty strong scientific consensus). Honestly though, I’m not the right person to discuss these nuances; I am in community with many trans people, but there’s a lot that I just simply can’t understand because I don’t have any direct lived experience of being trans. Furthermore, the trans community is far from a monolith, so discussions around terms like gender dysphoria, medical transition etc. ongoing.)