Hi there-
A lot would depend on the quantity, quality, and distribution of your skin after your weight loss (congratulations!), as well as the proposed areas for liposuction...
If your weight loss has left you with a lot of excess, poor quality skin, it is likely that you will not be happy with your lower back unless a lower body lift technique is used...
On the other hand, if skin excess in the area is minor, and the majority of the problem is remaining subcutaneous fat, you may be very pleased with the outcome of the proposed operation.
Your best bet is to visit a surgeon certified by The American Board of Plastic Surgery who has a lot of experience doing these types of procedures (ask to see photos and maybe even to speak to a few former patients). Get their opinion, digest the information, and decide what you think will make you happiest.