Intraduodenal infusions ( 240 mL , 60 min ) of saline ( 0 kcal , control ) and protein ( hydrolyzed whey ) loads of 30 , 90 , and 180 kcal were followed by an ad libitum buffet meal in 10 young ( 19-29 y ) and 10 healthy older ( 68-81 y ) men .