Whey-protein loads do not suppress ad libitum energy intake in elderly
Older men and women taking whey-protein drinks show a load-dependent slowing of gastric emptying and altered gut hormone secretion compared with controls, a recent study has found. However, whey protein does not appear to suppress subsequent ad libitum energy intake.
To determine the effects of whey protein on energy intake, appetite, gastric emptying and gut hormones in healthy older adults, researchers analysed eight older women and eight older men (mean age 72 years; body mass index, 25 kg/m2) on three occasions in which they received protein loads of 30 g (120 kcal) or 70 g (280 kcal) or a flavoured water control drink (0 kcal).
At regular intervals over 180 min, researchers measured appetite (using visual analogue scales), gastric emptying (using three-dimensional ultrasonography) and blood glucose and plasma gut-hormone concentrations (eg, insulin, glucagon, ghrelin, cholecystokinin, gastric inhibitory polypeptide [GIP], glucagon-like peptide 1 [GLP-1] and peptide tyrosine tyrosine [PYY]).
They also quantified ad libitum energy intake from a buffet meal (180 to 210 min; energy intake, appetite and gastric emptying in the men have been published previously).
At the buffet meal, older men had ∼80-percent higher energy intake than older women (p<0.001). Protein did not suppress energy intake in men and women compared with the control group (p>0.05). Sex had no effect on gastric emptying, appetite, gastrointestinal symptoms, glucose or gut hormones (p>0.05).
Whey-protein drinks load-dependently slowed gastric emptying; increased concentrations of insulin, glucagon, cholecystokinin, GIP, GLP-1 and PYY; and increased total energy intake (drink plus meal: 12-percent increase with 30 g and 32-percent increase with 70 g; p<0.001). Energy intake at the buffet meal inversely correlated with stomach volume and area under the curve of hormone concentrations (p<0.05).