Unfortunately, I know first hand of this behavior. It's something I've done for years when I'm eating alone. For me, it started when I was about 14 (I'm 28 now) and was concerned about my weight. I ate very little and chewed a lot. The more weight I lost, the more I did this. I continued for about two years until I had an "episode" with "gastritis" where I couldn't walk, sit up or do anything but scream with pain in my stomach. I went in the hospital for a few days and then my parents started monitoring my food intake. Once I started eating and not just chewing, I did gain weight, but had no more problems. I've not done it consistently over the years, but there are times when it happens. I'm not underweight, but please watch your child and she's so young...see if you can get her to talk to someone about it now. This is probably the first time I've ever mentioned it to anyone and I probably never will, as long as my health doesn't mandate that I do.