Matter cannot be created or destroyed, but may change form

I did a little bit of a science experiment yesterday. At 3:15pm I weighed 82.00 kilos. At 7:30pm I weighed 83.25 kilos. I went pee once, but not a lot. The only thing I put into my body was 7 litres of water, which weighs 7kg.

Although sometimes I feel like Shiva and that I can destroy worlds at whim, this has yet to be proven in practice. Further, the law of conservation of mass states that my ability to make nothing out of something is extremely unlikely (outside of the stock market of course). I can only sweat, breathe and urinate; which it appears that I did, to the tune of 5.75 kilos of water.

I am pretty shocked and I'll do it again just to make sure that I am not confused. That is a LOT of sweat, but then I am in the tropics and terribly out of shape. Yikes.