Whey Protein Drink Ingestion before Breakfast Suppressed Energy Intake at Breakfast and Lunch, but Not during Dinner, and Was Less Suppressed in Healthy Older than Younger Men

Ageing is associated with changes in feeding behavior. We have reported that there is suppression of energy intake three hours after whey protein drink ingestion in young, but not older, men. This study aimed to determine these effects over a time period of 9 h. Fifteen younger (27 +/- 1 years, 25.8 +/- 0.7 kg/m(2)) and 15 older (75 +/- 2 years, 26.6 +/- 0.8 kg/m(2)) healthy men were studied on three occasions on which they received, in a randomized order, a 30 g/120 kcal, 70 g/280 kcal whey-protein, or control (similar to 2 kcal) drink. Ad-libitum energy intake (sum of breakfast, lunch, and dinner) was suppressed in a protein load responsive fashion (P = 0.001). Suppression was minimal at breakfast, substantial at lunch (similar to-16%, P = 0.001), no longer present by dinner, and was less in older than younger men (-3 +/- 4% vs. -8 +/- 4%, P = 0.027). Cumulative protein intake was increased in the younger and older men (+20% and +42%, P < 0.001). Visual analogue scale ratings of fullness were higher and desire to eat and prospective food consumption were lower after protein vs. control, and these effects were smaller in older vs. younger men (interaction effect P < 0.05). These findings support the use of whey-protein drink supplements in older people who aim to increase their protein intake without decreasing their overall energy intake.