I have heard different reasons for this.
1. Jim Quinn told me GH makes you hold water in the intestines, resulting in a blocky waist.
2. Others feel GH & insulin lead to the growth of the fat around the internal organs (not the fat under your skin that bodybuilders lose when they diet).
3. Others opine that GH & insulin cause the internal organs to actually grow.
Who knows for sure? I'd love to see a guy who had a GH gut later when he is slimmed down to normal. How doe shis waist look then?