Is chitosan a safe way to achieve weight reduction?

Jury still out. There are more effective ways to lose weight than chitosan, like aerobic exercise and a good diet. The studies that have been done on chitosan are varied and not all are of good caliber. Some show minimal weight loss, others don't. Be wary of most supplements you see in gnc and online drug stores. The industry isn't tightly regulated at all and contamination with other substances is possible.
Not effective. Good studies have shown this not to be very effective in doing what people selling the product claim it will do. I wound not waste my money.