Circulating fasting total BA was not associated with obesity .
FGF19 was inversely and faecal BA excretion was positively associated with obesity .
Roux-en-Y gastric bypass ( RYGB ) and sleeve gastrectomy ( SG )  modulated BA metabolism , ie , increased BA and FGF19 .
Our results indicate that BA metabolism is altered in obesity .
Serum levels and clearance of bile acids are unaffected by jejunoileal bypass with 3:1 or 1:3 jejunoileal ratio.
Jejunoileal bypass may impair  liver function .  The hypothesis of the present study was that this may depend on the jejunoileal ratio of the segment left in continuity in a manner that affects the transport of bile acids from blood to bile . We investigated five extremely obese patients before and 29 patients 3 , 9 and 15 months after bypass surgery with a 3:1 or 1:3 jejunoileal ratio of the functioning segment .  Routine liver function tests , plasma disappearance rate of intravenously administered 3H-cholic acid and 14C-24-chenodeoxycholic acid , and fasting and postpr and ial serum concentrations of total 3-alpha-hydroxy bile acids showed no appreciable significant relationship with bypass surgery as such , time after surgery , or the jejunoileal ratio of the functioning segment
Circulating fasting total BA was not associated with obesity .
FGF19 was inversely and faecal BA excretion was positively associated with obesity .
Roux-en-Y gastric bypass ( RYGB ) and sleeve gastrectomy ( SG )  modulated BA metabolism , ie , increased BA and FGF19 .
Our results indicate that BA metabolism is altered in obesity .