Research
Hormonal
Roux-en-Y gastric bypass (RYGB) surgery improves glucose homeostasis and reduces appetite largely through altered gut hormonal milieus (increased GLP-1/PYY, decreased ghrelin) rather than solely through caloric restriction or malabsorption.
Bariatric surgery like RYGB works not just by making your stomach smaller, but by changing the hormones your gut releases, which helps fix diabetes and reduces hunger signals to your brain.
GoodSupportsHIGH confidence
Diabetes is rapidly ameliorated after RYGB and glycemic improvements often precede weight loss, supporting the view that changes in the gut hormonal milieu may be involved. An effect of surgery to increase PYY and GLP-1 levels has been reported... A postoperative fall or a failure of ghrelin levels to rise after surgery... has been observed.
Why this rating
The paper cites observed clinical phenomena (rapid diabetes amelioration, hormonal changes) but notes that definitive proof linking ghrelin suppression to appetite reduction awaits replacement experiments.
Source
The Gut and Energy Balance: Visceral Allies in the Obesity Wars
Michael K. Badman et al. · Science · 2005
DOI 10.1126/science.1109951
narrative_reviewCited 528×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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