[doublesCs]

No, this isn't true. There's no conservation of matter anywhere. If you take 2 hydrogen atoms and weight them, then bond them together in a hydrogen molecule and weight that, the molecule weights less than twice one hydrogen atom.

[ncmncm]

But you still have the two hydrogen atoms, before and after. They are matter. Tiny (really tiny!) differences in weight don't change that.

[doublesCs]

I guess when you said "conservation of matter" I interpreted that as meaning "conservation of mass", seeing as we're talking about weight loss.