Hi Oldtyke,
Thanks for the follow-up message. Not sure if there may be differences among people with GS as far as what triggers uncomfortable reactions...If interested in my food lists, or if others are, if you click on my name I've indicated that info in other posts...
Basically, I seem to have no problem with meat -- especially if I eat meat together with bread carbs, (also not a problem, generally). Best is a turkey burger on bread, no condiments.
Vegetables are a positive for me and some fruits such as watermelon. But certain other fruits -- particularly fruits that are heavy in acid seem to trigger the weakness and other symptoms for a day or longer following consumption, unless the quantity is small. In particular, I'll mention strawberries, oranges and other citrus, apples, pineapples and tomatoes.
Interestingly, some of these fruits, if cooked, seem to be less a problem -- tomato sauce is okay for me in small quantities -- better than raw tomato, apples if cooked are ok... Not sure about the other problematic fruits cited here in cooked form.
Your point re moderate portion size definitely applies to me. Relatedly, drinking water while eating seems to help. Not sure if it's due to dilutiuon or eating less due to less hunger as a result of drinking water while eating, or perhaps both circumstances.
I do have to watch my consumption of alcohol and only occassionally will allow myself a mixed drink, (perhaps 1x per month), with plenty of food, usually a margherita. Decent quality tequilla for me seems slightly less problematic than other alcohol.
Hope this info and other info I've posted elsewhere on the GS forums here is of help to you and others.