The effects of free fatty acids on gastric emptying, plasma cholecystokinin (CCK) and peptide YY (PYY), appetite and energy intake in humans are more potent than those of triglycerides.

Abstract

The effects of fat on gastric emptying, gastrointestinal hormone release and energy intake are dependent on the digestion of fat to free fatty acids (FFAs). There is limited information about the comparative effects of FFAs and triglycerides (TGs) on these factors. In animals, oleic acid inhibits energy intake more potently than an isocaloric infusion of its TG, triolein. Nine healthy males (23±2 years, BMI 22±1 kg/m 2 ) were studied on three occasions to evaluate the effects of (i) 40 g of oleic acid (“FFA”) (1830 kJ), (ii) 40 g of macadamia oil (“TG”) (1856 kJ) (both 600 ml oil-in-water emulsions stabilized with 4% milk protein and labelled with 15 MBq 123 I), or (iii) 600 ml 4% milk protein (“control”, 352 kJ), administered intragastrically, on gastric emptying, plasma CCK and PYY, appetite and energy intake. Gastric emptying of FFA was much slower than of TG ( P <0.05), with greater retention of FFA, than TG, in the proximal stomach ( P <0.001). Hunger was less ( P <0.05), and fullness greater ( P <0.05), following FFA administration, when compared with both control and TG. Plasma concentrations of both CCK and PYY were greater after FFA than after TG or control ( P <0.05). Energy intake was less after FFA, when compared with TG (control: 4754±610 kJ, TG: 5463±662 kJ, FFA: 4199±410 kJ*; * P <0.05 vs. TG). Free fatty acids empty from the stomach more slowly, but stimulate CCK and PYY release and suppress appetite and energy intake much more potently, than triglycerides.