A kilogram a day is a lot of weightloss. I think your body's slowing down is wise. Congratulations on getting close to your ideal weight. Personally, I think it's wise for us older ones to carry a bit more padding, for warmth, comfort, and because estrogen (produced by fat cells) protects the brain.
Perhaps your body is changing over from digesting fat to digesting other things, cleaning up the blood from pathogens and fibrous tissues--so important to get to that stage for complete healing, or so I've been reading. So again, congratulations are in order!