Most people are quite fixated on weight loss, but there are much better measures for health and diet.  The most important one is body fat.  If you are skinny as a rail but as a male have thirty percent body fat, you aren’t really doing so hot, and are probably at a risk for hyper-tension and the like.  Females start to be in trouble at about 40% body fat.  I think that the ideal percentage for men is something like ten, and for women roughly double that. 

The problem is that it is easy to step on a scale and get your weight, but figuring out body for is never really that easy.  There are some scales that claim to measure your body fat, but I have yet to experience one of these that seemed to really work with any kind of accuracy.  There are a few different machines that most health clubs have that do a great job, but probably the simplest way is to use calipers.  You simply take measurements of your fat (so much fun) and then run them through a formula that includes your weight, and you have a pretty good idea, and calipers are cheep, and while not quite so easy as a scale, easy enough.