I can feel the expansion of my belly, especially when I take a deep breath.
I tend to compare my belly with other bellies. If I think my belly is big, many of those bellies are huge! I find it hard to imagine myself getting that fat.
I have not noticed much change in my weight however the scale reading varies up and down several kilograms depending on food, water etc. At the end of a heavy gym session in which I drink more than 3 litres of water, I can weigh 2 kilograms more than at the start of the session.
It is mainly the greater width that I notice. Especially when I see my image in the mirror when I sit down.