I'm an adult male and I have around a 32 inch waist size and I can kind of fit into Pampers Cruisers size 7 diapers.
They don't fit completely correctly like they would on a real toddler or baby however the tabs stretch enough to where I can wear them without them popping loose.
I can also squeeze into Target size 7 diapers as well as parents choice size 7 diapers.
However if you really want to fit into diapers and be more comfortable then I recommend buying some adult sized disposable diapers that are made to look like baby diapers such as Tykables, Race Car Diapers, Abuniverse Little Pawz, Super Dry Kids, Rearz diapers etc.
I mostly use the Pampers and other baby sized diapers and wear them and then put the adult sized disposable diaper over the baby sized diaper which gives me extra absorbency.