I am in between frame sizes (54 & 56) for a Spec Sequoia and/or Roubaix (2007 models). The 54 feels good for torse. The 56 feels good for legs.
To those who have lost weight, do you find that the reach to the handle bars stay the same, decrease, or increase? Since I am in between sizes, I was curious as to how fit changes as your weight drops.
You should shop around to see if you can find a better fit from another manufacturer. Improper fit will cause cause discomfort and injuries. You shouldn't buy a bike that you'll 'grow into'. It might not happen the way you anticipate. Sounds like your longer legged, and shorter torso'd, try the treks. I have short legs and longer torso. I've never fit well on a trek because of that.
Having said that. I don't think there's much coorelation between weight loss and fit geometry. However, increased flexibility in the torso will allow you to reach further.
When I had my bike fit, they set it up so I was comfortable on the tops of the bars, and had to extend to ride the hoods or drops while maintaining proper posture. As my flexibility has increased, I can now ride on the hoods for a time in proper position. However, the basic geometry has remained the same.
ps. Improving flexibility requires stretching, and saddletime, both of which aid in weight loss, so of course there is that indirect relationship.
I lost about 40 pounds last year, from 6'4" and 270 to 230, and I found it MUCH easier to reach the bars that it had been. I suspect it was partly better flexibility, because I was stretching a lot, but mainly, getting my waist down from 43 to 38 got my gut out of the way.