Table 1.

Anatomic and physiologic changes due to bariatric surgery

	Stomach	Duodenum	Proximal intestine	Distal intestinal
RYGB	Decreased capacity to 15-30 mLChyme bypasses 90% of stomachDecreased gastric transit time	Bypassed by chyme	Proximal jejunum bypassed by chymeRapid exposure of distal jejunum to chymeBile mixes with chyme in proximal ileum	Earlier exposure to chyme
AGB	Restrictive band around gastric cardiaDirect pressure on vagus nerves	No alterations	No alterations	No alterations
BPD/DS	Decreased capacity to 60-150 mL85%-90% of stomach removedAccelerated gastric emptying by 2-fold to 3-fold	Bypassed by chyme	Chyme bypasses jejunum Rapid exposure of ileum to chymeBile mixes with chyme in distal ileum	Rapid exposure to chime
SG	Decreased capacity to 60-150 mL85%-90% of stomach removedAccelerated gastric emptying by 2-fold to 3-fold	More rapid exposure to chyme	Possibly earlier exposure to chyme	Possibly earlier exposure to chyme

AGB: Adjustable gastric band; BPD/DS: Biliopancreatic diversion with or without duodenal switch; RYGB: Roux-en-Y gastric bypass; SG: Sleeve gastrectomy.