In my experience it is fairly easy to assess whether a patient will react well to the VASER treatment and suffer from lax skin or not. If there is any doubt that there is going to be wrinkly skin then the patient is not a candidate and I decline to treat them.
The term "Loose skin" applies to the mobility of the skin. This occurs when the interface between the muscle and skin becomes less elastic and allows the skin to move freely over the muscle and connective tissue. As we become older our elastic tissue becomes a little lax and thus allows for the skin to be a little more mobile.
This becomes especially noticeable when someone has lost a few stones. Compare this to a ballon that deflates - the membrane becomes flaccid as the volume depletes. Similarly the skin becomes a little "wobbly" over the muscle. VASER does help a little with skin tightening, but there is a limit as to how much will take place.
I hope this explains and reassures you a little with regards to skin laxity.