The more you weigh when you first start trying...

Most people who are obese or morbidly obese think they are "big boned" or "thick" or have a large frame. In the end, when you get a low body fat, most people fall within a very small distribution of weight based on height.

People underestimate their fatness.

Some people are okay with remaining fat, but just being less fat.

You can determine your frame by your wrist size. In fact, I am big boned (woman with 7"+ wrist regardless of my weight). I can still be lean and have been in the past. I also tend to build and keep muscle easily, so as I lose weight, I don't care if I lose some muscle, because I know I can adjust for it later quite easily.

Here's an interesting article on how to test for bodyfat, but in summary, the only surefire way to get an accurate reading is to do an autopsy. Other methods will show a range of results for the same person.

http://www.washingtonpost.com/wp-dyn/content/article/2008/05/02/AR2008050203388_2.html?sid=ST2008050500910

I lost an inch off my wrist as I lost weight, so it's not completely full-proof.

Very interesting responses.
I'm gonna come fromthe othe side. I was always smaller in High School and even after I had my first daughter Ilost all of my baby weight which was a whopping 60+ pounds.
Pre-pregnancy I was 23 years old 5ft 3in and 130-135 pounds. Day of delivery I was 190 or so pounds!
Gained the same weight with 2nd kiddo and got pregnant with the 3rd before the 2nd one was even a year ols so I didn't lose all of the 60 pounds from number 2 and then I just never did lose it!
I startd MFP weighing 165 pounds(I had already lost 10 pounds before I started on here)
So....jsut to get to 135 seemed like a lotof weight to me because it had been sooo long since I had been that small! I told myself that if I got stuck at 140 I would be fine with that!
UH so not true! I hit 140 and was totally motivated to get that 135 back on the scale and now...I'm still going to drop a few more pounds. I"m down to 133 but according to my height the "normal" range for me is 104-140....104 is a bit drastic but I see me at 133 and it is not at all what I remember it being so I feel like I need to lose a bit more!
Once you get close to your goal you will probably change your mind.
For me, I started out just wanting a lower number on the scale...now I want to be fit and healthy not just small and jiggly. I want to firm this stuff up!
It's all about where you feel comortable and some people learn things about themselves that they never knew before. Some people simply want to drop weight. Some people want to drop weight and firm up and some people decide to become a totally different person. It all depends on how you embark on this journey and where you let it lead you.

I think it's because we can't imagine being that low.I speak in kg (and my son has disappeared with the calculator to convert) but I can't imagine below 80 which is still overweight for my height (166cm) so I'm only aiming for that. If or when I get there, then I will readjust my goals.

That's it exactly. My first goal weight is 90kg/200lbs. I haven't been that since Year 10/11 of high school. So 1999/2000. The weight I am now I haven't been in eight years. Everyone whose known me a long time keeps stating 'You look like you did when you were 18' because I have a neck again. To get to my (current) ultimate goal weight of 70kg/154lb puts me at just in the normal weight category. I last weighed that at FOURTEEN. That's over half my life since I weighed that. (my grandparents think it's too low) It's a terrifying thought. To think of going to under 60kg? (still mid range for my height) I don't ever remember weighing that little. So once I get to 70kg I'm going to reevaluate where I'm at. If I still have more to lose I'll lose it. (I'll probably be losing 2.5kg anyways as I can then say I've lost half my body weight ) If I like it I'll figure out my range and stay there.

I suspect it's partly because very large folks are often trying to lose weight for health rather than appearance, so just getting down to a level where you (me!) are no longer clinically obese and are merely overweight will have huge health gains.

Certainly that's my first goal. If I can get anyway near the healthy weight goal I will be delighted. I am big structured-not big enough to justify my current weight or anything like it, but when I was fit (heavy weight lifting and rowing) I was very close to the top of the healthy weight range despite having a low body fat percentage. These days, I would, no doubt have to be a fair bit lighter to be the same size as I don't have the same muscle mass, and injury and osteo arthritis make it harder to re acquire it.

Interesting observation. I have my goal set at 183 because that is the high end of a normal BMI for my height (6'). I plan to adjust that lower once I get there, but I think somewhere between 155 and 165 will be my ultimate goal. I guess since its been so long since I was in the range, I didn't want to pick something too low and then never reach my "goal". I'd rather tinker with it when I see what I'm working with.

I'm 5'4 and my goal at the moment is 128lbs. I've set it at 128lbs because a few years ago I was really poorly and I lost a lot of weight very quickly [and put it all back on once I was better!]. I can remember between 128-138lbs I felt okay about myself. However, at 118lbs I started to look like I had a lollipop head and certainly by 108 [which was slightly underweight] I looked really poorly.