Lighting is a very important factor in how you look in a mirror. In my workout mirror, I often look more defined and leaner, because the lighting is from a lamp over in the corner (indirect lighting is the way to go!). In my bathroom mirror, more cellulite shows, and I don't look as lean, because the light comes from a bright overhead light. (peach-tinted lighting, or candlelight is the most flattering!).
I think it's interesting that mirrors don't really reflect how we look to others. There is a special mirror in a small physics display at the U. of Wisconsin-Madison that shows you the way you look to others (rather than "flipped" right-to-left). It really does change how you look.
Wouldn't you think that stores would want to put the most flattering mirrors and lighting in their dressing rooms to encourage you to buy? I was in the local Penney's once, and the lighting in those dressing rooms (and maybe also the small space so you are too close to the mirror) was aweful! But, as Donna suggests, that might be fore the better.
