I think it depends on how much you have to lose.
If you have only a little bit to lose, you may be successful not using any syns.
However if you have quite a bit to lose, depriving yourself of syns early on, could mean eventually you may start to feel like you are missing out on stuff and are more than likely to fall off the wagon. Also if you have no syns from the start, when you do get down to those last few pounds, you will have nothing to cut back on to try and boost your weightloss.
With that in mind, I believe it is recommended that you do at the least have 5 syns a day, up to a maximum of 15.