Surgeon told me 170 pounds was unrealistic

I wonder if they say that to not get our hopes up? When I said I wanted to be 150 (I am 5'6, so that would put me in the high end of normal) I was told a more realistic goal would be 170... I remember saying to my husband well 170 is still a lot better then 265, but I will still shoot for 150.

Then on my recent surgery to correct an arm of the Y in my RNY (and an internal hernia and some adhesions and orientation of my intestine) in Dec , while I was recovering the nutritionist came to visit me in hospital to go over my diet post op until my intestines heal, she even said in her classes for wls they tell people that realistically they may never reach a normal BMI, 

my thoughts are that maybe some don't, so they want to be sure we are made aware of this and not be set up for disappointment. so as long as you follow your plan, you will reach your own sweet spot which will be healthier then doing nothing at all :) I have a feeling with your determination you will reach your goal!

My surgeon's office told me the something similar. When I first saw them, and was in the 290's they asked me what I wanted to weigh and I said 150. They told me that realistically RNY might only get me to 195, MAYBE 175. Which we all agreed was WAY better than weighing almost 300 pounds. I am still fighting to get to 150, and maybe even a little less, but I think they do tend to aim low in numbers so people don't have crazy expectations.

There are some reasons my surgeon said that getting to a "normal" BMI would be difficult. Depending on how long we are morbidly obese, everything about us is oversize, including bones, internal organs, etc. Those things, especially bones, may not shrink to normal after surgery, so we weigh more. Also, the extra skin and pockets of fat can add up to enough weight to make a difference.

That being said, at 6'3", my surgeon's goal was 250, my own goal was 225, and my current weight is 185. I think if you follow your plan, you could hit 170.

You have a point.  We do have larger bones due to being overweight and hopefully our bones will not shrink.  Losing fat is good, losing bone is not.  And most of us will have some extra skin.  But in most cases that extra skin doesn't weigh all that much.  I've known people that had loose skin on their stomach hanging down so low it caused difficulty walking and when they had it removed, it might have weighed ten pounds.  Sometimes less.  That extra skin just isn't as heavy as you might think.

Why on earth would the size of anyone's bones change to due weight?  Doesn't make any sense.

I just had my shoulder joint replaced. The implant includes a 6  inch plus long titanium spike which goes down the center of my upper arm bone. I reminded the surgeon that I'd had WLS and asked if that would change his decision of which size and type of implant to use.  He laughed and said no, I'm implanting this in your bone, not the fat, so the size won't change.

Sometimes I wonder about the "science" that is stated as fact on such forums.  Always good to ask your doctor for clarification when he/she gives you information you do not immediately and fully understand.

We are in partnerships with our health care providers and good communication is a key to the success of those partnerships.

I'm sorry it doesn't make sense to you, but it doesn't make it less true. Everyone's bones and bone density varies. Morbidly obese bones are heavier.

I'm always willing to learn, but I wasn't finding anything about bones being larger  (i.e. longer, thicker, greater circumference, etc.)  when I made a Google search.  Are you saying the bones of the MO are denser rather than larger? There is a difference between the cellular density and overall size. 

From another thread: http://press.endocrine.org/doi/full/10.1210/jc.2003-032162

And from the linked article:

"Several facts must be kept in mind with regard to obesity, vitamin D metabolism, and bone. First, body weight is a major determinant of bone mass, and bone mass is increased in obese subjects, particularly at weight-bearing sites (9, 10). This is attributed to increases in mechanical loading (11). Bones of obese individuals are larger and therefore less likely to fracture (12)."

If you google something like "effect of obesity on bones" or "obesity and bone mineral density" you will find numerous articles and studies that find obese people have greater bone mineral density.  Our bones get bigger/denser to carry our weight.

Some of the reasons to exercise after WLS is to preserve lean body mass, including muscle and bone. While on an extended very low calorie diet, everyone will lose some   lean body mass, but those who exercise will retain more than those who don't. Lifting weights and other weight bearing exercise, even walking, will preserve more bone and muscle than non-weight bearing activities. So exercise is important for more than just burning calories.