Background: The dogma that persisted for many years was that
malabsorption plays a significant role in contributing to the weight loss
following bariatric surgery. The aim was to assess for evidence of
malabsorption after bariatric procedures; adjustable gastric banding (AGB),
Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion-duodenal
switch (BPD-DS).
Methods: This cross sectional study recruited participants into four groups:
obese controls (n=7), AGB (n=6), RYGB (n=7) and BPD-DS (n=5).
Biochemical tests were used to assess; (i) entire gut: sulphasalazine test for
oro-caecal transit time (OCTT) & plasma citrulline for functional enterocyte
mass. (ii) foregut: faecal elastase-1 (FE1) for exocrine pancreatic function.
(iii) mid-gut: Lactulose:rhamnose (L:R) ratio for gut permeability, faecal
calprotectin (FCp) for gut inflammation & plasma and urine bile acids (BAs) for
BA metabolism. (iv) hindgut: Faecal fat (Ffat) excretion for fat malabsorption.
Results: (i) entire gut: There was no difference in OCTT (p=0.935) or
functional enterocyte mass (p=0.819). (ii) foregut: FE1 was lower in the
RYGB vs. the control group (p=0.002), with no difference between other
groups (all p>0.05). (iii) mid-gut: L:R ratio was higher in the BPD-DS vs. the
control (p=0.012), AGB (p=0.016) and RYGB (p=0.012), with no difference
between other groups. FCp was higher in the RYGB vs. the control (p=0.016),
with no difference between other groups. The fasting plasma and urine BAs
were elevated in BPD-DS vs. the control, ABG and RYGB (all p<0.05). (iv) hindgut: The BPD-DS had higher Ffat excretion vs. the control (p=0.038),
AGB (p=0.046) and RYGB (p=0.024). The RYGB had higher Ffat excretion vs.
the control (p=0.033). There was no difference between the RYGB and AGB
(p=0.808).
Conclusion: There was no evidence to support the notion that RYGB causes
severe malabsorption of fats or sugars. However, BPD-DS does cause fat
malabsorption.