Hi Peter
I have type 2 and have had a subtotal colectomy and proctectomy so I don’t have an internal pouch but a stoma bag, however I had similar problems when taking metformin , stomach cramps, excessive wind and watery output which would cause my bag to have a major leaks when at work and out shopping etc
It was extremely embarrassing so I decided not to take metformin and try a lchf
Diet instead, it has been extremely successful my hba1c has come down from 7.9 to 5.6
I haven’t experienced any adverse affects from the increased fat intake (although It might be different with an internal pouch) and I have found that by not eating the bulky starchy carbs (pasta,rice,potatoes etc) I have a lot less output and have to empty my bag much less frequently. I know internal pouches are more difficult regarding diet and control.
This is just my experience and everyone is different so I’m not recommending lchf, I guess it wouldn’t be suitable for you and as always it’s best to discuss any changes with you GP