How to lose wieght quiclky?

I do not work out but I do have a job that entials me to walk a LOT and other things that could be considered as exercise. I only eat one meal a day then snack the rest of the night not on junk food but as I p by the kitchen getting somethign to eat on the way to the next station. I am dietary manager and work around food all day long... I dont eat a lot of junk food or fatty foods but still am gaing weight.