I've always had longish hair (it's curly, so while grows fast it doesn't look it) and I thought it looked good on me at my starting weight and at my goal weight. I do admit I would "hide" behind my hair (I've got A LOT of THICK hair so it's always out and big) because I thought it made me look thinner. Now I just embrace my hair because it's unique.
I think much of it largely depends on one's face though. Certain hairstyles look better or worse depending on people's facial structures. It also depends on the type of hair, how it grows...I guess it work to say that one hairstyle works for overweight people and another works for thin people...everyone's faces and hair are different after all!
My mother always wanted me to have a close-cropped short hair cut, because she said it makes my face look thinner, and I think she was right (for me, not for all overweight women), but I also think it makes me look ridiculous - a thin face on a huge body, like a large snowman with a teeny, tiny baseball-sized head.
I don't think length is as important as fullness. A tight ponytail makes my head look just as small as a pixie cut, so I like volume. Right now, I have long hair, and I do often put it in a ponytail (even though it does make my head look too small), but I prefer to have it fuller so that my head looks more balanced with my body. So while it does make my face look fuller, I don't feel like a pinhead.
I think it really depends on not only your face shape, but what you like.
My Etsy shop (currently closed for the summer)
Back when I was at a much healthier weight, I decided to cut my hair. That's when I realized a shorter hairstyle will never look good on me no matter what my weight. Right now my hair just goes down to the top of my shoulder blades. I would probably grow it a little longer and maintain the length, but probably won't go any longer than that. my hair needs the weight of long hair in order to keep it from going poofy.
My hair is wavy - that 'wonderful' place between curly and straight. And very prone to frizz. I recently gave up my straightener and decided to stick with my natural hair type.
I think it depends on your face shape. I've seen overweight and obese women who look great with short hair. I look aweful with short hair. But mine is way too long right now, chopping off 5 inches this weekend for a good medium length
I keep mine pretty long because short hair just doesn't suit my face. I've seen girls who are bigger than me with short hair and it looked fantastic on them so it's not really a weight thing I don't think.
I agree with others that it depends on face shape/cut/type of hair.
I've seen some larger women with long hair who can pull it off really well. I've also seen it look really bad (the example I'm thinking of the woman had a very round face and super straight long hair it might have just been the cut too but it didn't match very if that makes sense?). It seems like the styles that I found the most flattering that were longer tended to have more body to them (wavy or curly). However, I could also imagine a scenario where someone had "too much" hair so in the end you just have to experiment a bit.
I guess long story short, maybe talk to a hair dresser and get their opinion. For me I always preferred to have short hair when I was larger. I have a round face but never carried a ton of weight in my face either. Short hair gave me a bit more volume but not an overwhelming amount. Also, when I have long hair that almost always means a ponytail the vast majority of the time and me at my highest with a ponytail was not the most flattering site in the world mostly because it would make my body look a lot bigger than my head. So maybe if I wasn't so lazy I couldn't pulled off long hair better.
ETA: DH always prefers me with short hair no matter the weight but I've had other boyfriends (obviously before meeting him!) that liked me with long hair better regardless of weight so who knows!!!
I've had both while heavier, and seeing myself heavier with shorter hair looks worse to me when seeing pictures. I think, for me, it accentuated how big my face was However, I don't believe it to be true for everyone as, like said above, everyone's face is different
I'm going to be extremely honest because of the anonymity of the internet here, but I have frankly never seen a big girl with a short hair cut that made her look better. I'm with kaplods- it DOES make your head look smaller sometimes, but that's generally not a good thing. Now, maybe I'm just not remembering all the bigger women I've seen with short hair cuts, and maybe there are some out there that look great that I just haven't seen yet, but for the most part, I think chin length or longer helps.
Around Halloween, one of my female friends came over wearing a costume that involved a wig. Her hair is usually very, very short, and she is a bigger girl. The wig was long and full, and she looked SO much better-more feminine and more proportionate- wearing this cheapie Halloween wig than she does from day to day in real life!