I'm speaking from th standpoint of a former anorexic. Anorexia, like what is documented in the book you're reading, is a type of body dysmorphic disorder. Between the ages of 16 and 17, I lost 107 lbs in 10 months. At my lowest, I was 124 lbs at 6'1....pretty scary. At that time, I faced heart failure due to starvation. I was subsequently admitted to a psych ward where I made progress towards gaining weight after being threatened with a stomach tube. Upon leaving the hospital, I was back at a healthy weight, yet was by no means cured. I then went on an eight year drug and alcohol spree, going to any lengths to get over many of my insecurities. This spree started with the small-time such as alcohol and marijuana and ended with me slamming heroin before I went to work as a teacher in the morning. Life was crazy, to say the least. I am now three years clean and sober after admitting myself to rehab. I will tell you this..the feelings of being fat have never completely left me. That said, bodybuilding has given me an perception of my body that I have never had before, and in the past three years, I have started to get to a point where I like my body. Now I'm in the middle of my first cycle, and considering my past, I really have to keep an eye on my use.
With all this said, I do not believe...and I am speaking from the standpoint of someone who has done a lot of research on all these, has a PhD (though not in any medical field), and has spent 1000s of hours with psychiatrists and psychologists...that anorexia, your so-called bigorexia, and even drug addiction are things that a person is born with. That said, I see all of these as types of compulsive behavior that certain people are definitely born with a predetermination for. Science can prove that genes do determine one's predisposition towards compulsive behavior. Now, whether or not this compulsive behavior manifests, as well as how it manifests (bigorexia, anorexia, bulimia, drug addiction, etc.) is likely a reaction to environmental stimuli. At the age of sixteen, something made it alright for me to be anorexic, but not a drug addict. Later, drug use became a welcome refuge (and honestly saved my life for a while). Now, some may say that I am addicted to working out...at least that doesn't hurt me that much.
So to answer your question, are people born with bigorexia? No.
Can people develop bigorexia? Yes
That said, are people born with a predisposition towards compulsive behavior? Definitely.
So, if you are worried that you have a problem and do indeed have bigorexia, ask yourself these questions, the answers to which might be very telling:
1.) Have you ever engaged in any other compulsive behavior, even if that behavior plays no role in your life now?
2.) Have you ever drank or used recreational drugs excessively for a period of time?
3.) Have you ever been a workaholic?
If you answer yes to any of these questions, it is my opinion that it is highly likely that you suffer from compulsive behaviors. In which case, the possibility that you have bogorexia goes up.