There are a lot of stereotypes surrounding weight in the society that we live in.  We equate thinness with health, whereas those that are overweight, are considered unhealthy.  What we need to consider is metabolic health rather than outward appearance.  This is an article from The New York Times that summarizes some current research on weight vs health.

We all come in different shapes and sizes.  I get worried when a guest has a body fat percentage in the healthy range but are desperate to lose 10 more pounds.  Where is the weight going to come from?  There are often more reliable indicators of health than just the weight on the scale.