The present invention is directed to constructs, compositions and methods for modulating platelet-type 12 lipoxygenase (12-LO) in adipose tissue in vivo. Specifically, the invention provides constructs encoding expression-inhibiting oligonucleic acids, e.g. antisense and RNA interfering (RNAi) molecules, targeted to a platelet-type 12-LO gene or a transcript thereof, which are capable of reducing or silencing platelet-type 12-LO expression specifically in adipocytes and pre-adipocytes. Vectors comprising these constructs (including, but not limited to, viral vectors), compositions comprising them and methods of using same for the treatment and amelioration of conditions associated with excess fat cell mass and obesity are also provided.