Probably mostly body fat after a certain point. Your abs, obliques, and low back all contribute too though.
Robert, or anyone else, how much waist size increase is attributable to actual fat around the waist vs the muscles of the "core" growing? If I hadn't gained ANY fat, would my waist size still have grown, just due to muscle growth, and if yes, is there a general rule to how much this waist growth would be?
Hope this makes sense.
Probably mostly body fat after a certain point. Your abs, obliques, and low back all contribute too though.
If you are referring to your abdomen only (not the entire waist) then I would probably guess it's marginal. The fat looks less squishy as it happens though.