Pre-sleep protein consumption has no impact on next-day appetite, energy intake and metabolism in older individuals

Background: Appetite, energy intake and dietary protein intake tend to decrease with age and may contribute towards the development of sarcopenia. Pre-sleep protein stimulates overnight muscle anabolism in older adults and may potentially mitigate sarcopenia progression. However, protein is the most satiating macronutrient and acutely affects appetite, energy intake and metabolic rate. Therefore, the aim of this study was to investigate the effects of pre-sleep protein ingestion on next-day appetite, and next-morning energy intake and metabolism in older populations. Methods: 12 participants (8M,4F, aged 71.3 +- 4.2 yrs) were recruited for a single-blind randomized cross-over design study. Participants completed 3 experimental visits, during which they consumed one of three beverages; casein protein (CAS; 40g protein, 168kcal), maltodextrin (MD; 0g protein, 168kcal) or a water placebo (WP; 0g protein, 0kcal) prior to sleep. Next-morning metabolic rate was assessed using indirect calorimetry. Ad libitum energy intake was assessed at a buffet-style breakfast, and subjective ratings of appetite were obtained prior-to and over 24 h after protein ingestion. Results: There was no effect of CAS consumption on subjective appetite at any point during the experimental trial compared with MD or WP. Relative energy intake at breakfast (CAS: 6.8 +- 3.1 kcal.kg-1, MD: 6.9 +- 3.2 kcal.kg-1, WP: 7.2 +- 3.4 kcal.kg-1) and next-morning resting metabolic rate (CAS: 1874.4 +- 468 kcal.day-1, MD: 1645.4 +- 424.4 kcal.day-1, WP: 1805.6 +- 399.8 kcal.day-1) were also unaffected. Conclusion: Our findings suggest that pre-sleep protein can be implemented by older adults to augment daily protein consumption without impacting next-day appetite or energy intake. Further research should assess whether these findings are applicable in chronically ill and hospitalised populations who are at higher risk of sarcopenia and associated comorbidities.