Based on height and weight...

[Shaman]

I'm about 5' 8" and 170 lbs, I've lost about 40 lbs. I've still go t large MBs, would that be fat or gyne? Can you even know based on height and weight? Would former stretch marks mean anything? It's mostly normal when I throw my arms back and up...

[Achilles]

I don't think it's possible to tell by height and weight, go see a PS that has experience with gyne and he/she will let you know.

[Allan7865]

I agree, go see someone.

[Paa_Paw]

Most girls are also nearly flat chested with their arm up and back as you described.

Weight loss may help but often it does not. Many of us simply have fatty deposits there which are highly resistant to either diet or exercise.

To make things worse, excess fat can bring with it an increase is Estrogen.

Another element in the mix is the possibility that the skin in the breast area may have been stretched beyond its elastic limits and will not now shrink back and you are left with saggy breasts.  The stretch marks may me a clue that this is the case.

For best success, you will have to have your weight in normal range,  See a good Doctor (usually a Reproductive Endocrinologist is preferred)   Then, you might want to see a surgeon.  But for the best results, don't skip any steps.