Body dysphoria is a feeling that there is something wrong with the configuration of the body, apart from any documented physical conditions. It is often contrasted with simple gender dysphoria, but some people instead portray gender dysphoria as a symptom of the same underlying condition. As I wrote a few years ago, there is an argument that body dysphoria is an innate “medical condition” deserving special protection. In that post I discussed multiple cases of body dysphoria appearing in adulthood, which contradict the idea that it is always innate.
So if not everyone with body dysphoria is born with it, how did those people get it? There is an alternative explanation for body dysphoria, based on the theory of semantic frames, that body dysphoria arises when gender dysphoria and transgender desire interact with the world. There is no reason to believe any of them are innate.
I also want to note that body dysphoria seems to be frequently triggered by the presence of others, or at least by people imagining how others would see them. The symptoms of body dysphoria – shock and distress – bear a strong resemblance to the feelings that many people feel when they are misgendered – classified by gender in a way that contradicts their intentions. The explanation that I give for body dysphoria also explains the reactions to misgendering. In fact, they are the same reaction, only with different triggers.
The way I’ve presented the concept in the past is that body dysphoria is a feeling of discomfort with the body, specifically the idea that there is something wrong with the body, that the way it appears is not the way it truly is or should be. By contrast, I’ve defined gender dysphoria as a discomfort with gendered expectations imposed by other people. I’ve also tried to separate gender dysphoria from transgender desire, the desire to be seen and accepted as a member of a different gender. Many people experience all three feelings, but some people only experience one.