Valid point, but your starting mass also increases.
Then there's also that if the measurement changes, the results can become pretty bizarre. Say, you are on a diet for one month. At the start of the month, the kilo prototype weights 1 skg and at the end 1 ekg = 0.9 skg. You measure yourself at the start of the diet, and get that you weight 100 skg. You use some very precise diet-fu to draft a program that should see you losing 5 skg during the month. And lo and behold, you manage to stick to the program and loose exactly 5 skg.
But at the end of the month, when you measure yourself against the now-lighter prototype, you get that you now weight 106 ekg. So, you actually achieved your target and lost 5 kilos, but meanwhile ended up with 6 kilos more body mass than before the diet!
(Disclaimer: real changes in the prototype mass are of course way, way smaller.)
Ha, love it. I wonder if that's like receiving dividends on shares in a foreign currency. Your share value (weight in kg) changes over time due to currency fluctuations (lowering value of 1kg), but the dividends paid out (variable weight loss for a given time period) are also affected by the same currency fluctuations (lowering value of 1kg).
Then there's also that if the measurement changes, the results can become pretty bizarre. Say, you are on a diet for one month. At the start of the month, the kilo prototype weights 1 skg and at the end 1 ekg = 0.9 skg. You measure yourself at the start of the diet, and get that you weight 100 skg. You use some very precise diet-fu to draft a program that should see you losing 5 skg during the month. And lo and behold, you manage to stick to the program and loose exactly 5 skg.
But at the end of the month, when you measure yourself against the now-lighter prototype, you get that you now weight 106 ekg. So, you actually achieved your target and lost 5 kilos, but meanwhile ended up with 6 kilos more body mass than before the diet!
(Disclaimer: real changes in the prototype mass are of course way, way smaller.)