I have always seemed to look like my neck was not washed good, even when I was a kid, and at a more normal weight. My mum would get so frustrated with me, admonishing me to wash my neck, and threatening to take me down and scrub me until I was clean! I have rubbed and rubbed and rubbed and rubbed and the dern thing is STILL there! My friend's nephew is only 4, but he is really overweight, and they were told by his dr. that the darkish ring around his neck was a precursor to diabetes... and sure enough, the poor kid got it. I decided to do some checking on it, and it sounds like what I have had on my neck all these years. It is embarrassing at times, because I love to wear my hair up, and it makes my neck look like I have been rolling in the dirt! I am not aware of it being anywhere else.