I know very little about the state of medical and neurological research on transgenderism and, while I'm very interested in educating myself more on this issue, I'd rather not get too deep into questions of the "reality" of gender.
What I
do know is that there are many people whose fundamental wellbeing and happiness depends on seeing their gender identity recognized and respected.
This makes transgenderism real, regardless of anything else.
Its almost impossible to lose weight once you gain it,
Can't confirm. My weight fluctuates a good deal based on the factors one would expect--how I'm eating and exercising and my stress levels. (This is actually unhealthier than being consistently slightly or moderately overweight, but it does mean that I could keep the weight off if I were able to eat well, exercise, and avoid constant stress for a decent length of time.)
I have the same experience. I once gained 15 kilos over the span of nine months or so, and then lost them over the fifteen (though for me it was all through changes in my eating habits - I've never managed to exercise).