The brain gut connection is incredible. For years I suffered with terrible IBS where I would almost always get nauseous after eating and would often need to immediately go to the bathroom. I also had a very difficult time gaining weight. I tried all kinds of drugs - prescriptions to treat nausea, malabsorption, even gastroparesis (slow emptying of the stomach). Nothing worked and a few of the prescriptions were nerve…
I am not surprised that the brain-gut circuit affects the sympathetic nervous system. I find that when my symptoms start getting very bad my heart rate variability drops basically to 0 (with loud, thunderous heartbeats). When things are good I don't notice my heartbeat whatsoever. Symptoms improve basically when I stop eating.. which is not a treatment plan.
I find it strange that my gastroenterologist does not even contemplate cases involving gut dysbiosis. I ask all of the relevant questions and the answer is "dysbiosis is not something we treat". And he's a gastroenterologist for christ's sake. He literally said to me "Get used to it. Some days you will have good days and some days you will have bad days". Modern medicine for you.