Effects of Timing of Whey Protein Intake on Appetite and Energy Intake in Healthy Older Men

Background Protein-rich supplements are used widely to prevent and manage malnutrition in older adults. We previously showed that 30 g whey protein ingestion, 3 hours before a buffet meal, suppressed energy intake in young, but not in older men. Information about the impact of the timing of ingestion of protein drinks on the suppression of energy intake in older adults is lacking. Objective The aim of the study was to determine the effect of the timing of whey protein ingestion on appetite and subsequent ad libitum energy intake in healthy older men. Design In a single blind, randomized design, 16 older men were studied on 5 occasions, on which they consumed a whey protein drink (30 g/120 kcal, 140 mL) 3, 2, 1 hour(s), or immediately before a buffet meal, from which ad libitum energy intake was quantified, and isopalatable noncaloric drinks (∼1 kcal) at the remaining time points. On the control day, noncaloric drinks were ingested at all time points. Perceptions of appetite and gastrointestinal symptoms were determined, by visual analog scales, throughout the study days. Results There was no effect of the timing of protein ingestion on perceptions of appetite and gastrointestinal symptoms (P >.05) or energy intake at the buffet meal (3 hours: 888 ± 49 kcal, 2 hours: 879 ± 56 kcal, 1 hours: 909 ± 47 kcal, 0 hour: 892 ± 51 kcal, control: 930 ± 49 kcal, P =.94). Total energy intake (ie, preload + test meal) was higher on the protein days compared with control (82 ± 24 kcal increase, P =.003). Conclusions In older men, ingestion of 30 g protein increased total energy intake, irrespective of the time of intake in relation to the meal. These observations support the use of “pure” whey protein drinks to increase overall protein and energy intake in older adults at risk of undernutrition.