Hi,
While on insulin, I have lost about 3 stone. That is about 20 percent of my weight, I'd say.
I have reduced my insulin by around 20 percent also. I was on around 42 units of premixed insulin at the start. My insulin now for a day of 'normal healthy, carb rich diet' would be around the 32-34 units total. As I am low carbing, though, I need less of my rapid insulin and often land around 20 units with 16 of those being basal.
When they set up insulin regimes to begin with, they calculate it based on weight and then adjust.
For a type 1, the starting point is 0.1 units per total body weight in kilo's, then half of that as basal. That goes up to around 0.3 units per kilo.
For type 2s, the starting point is more like 0.3 going up to around 0.5 units/kilo. That is generally because type 2s tend to be more insulin resistant.
So yes, that observation makes perfect sense. And in any event, your meter results and your hbA1c are the things you should trust. So as long as they are good, all is really well.
-M