Acute Effects of Ketone Monoester Co-Ingestion With Dietary Protein on Whole-Body Phenylalanine Oxidation, Phenylalanine Retention, and Myofibrillar Protein Breakdown Following Resistance Exercise in Older Males

The goal of this trial is to determine if ketone monoester supplementation in conjunction with protein supplementation in the post exercise period can augment whole-body protein metabolism following resistance exercise in older trained males. This trial will compare the difference in phenylalanine metabolism between the ketone monoester and control conditions. Secondary outcomes including plasma amino acid, plasma insulin, plasma glucose, capillary blood beta-hydroxybutyrate concentrations and whole body myofibrillar protein breakdown rate (k) will be explored as secondary measures. Ketone monoester supplementation with protein in the post-resistance exercise period will be compared to the control condition of just protein in the post-resistance exercise period.

Inclusion Criteria: 1. Adult male aged 65 years or older at time of initial screening. 2. Generally healthy (no uncontrolled diseases or conditions) as determined by health history, and if necessary, physician clearance. 3. BMI between 18.5 and 30 kg·m-2 (inclusive) at time of initial screening. 4. Maintenance of a stable body weight for at least 3 months prior to participation and willingness to maintain this weight during the duration of this study 5. Maintained stable use of medication and supplements (which are not limited by the exclusion criteria), and stable dietary and lifestyle habits for the last 3 months prior to screening and agree to maintain them throughout the study 6. Minimum 6 months of resistance training experience with a minimum of 2 sessions/week 7. Able and willing to understand and agree to the requirements and restrictions of this study and provide written informed consent Exclusion Criteria: 1. Presence of cardiovascular, metabolic, renal, hepatic, neuromuscular, or gastrointestinal disease that could interfere with study participation or data interpretation or make the resistance training unsafe 2. History of severe cardiovascular events (myocardial infarction, stroke, severe hypertension) 3. Any musculoskeletal injury that would prevent completion of the resistance exercise protocol 4. Ketone supplementation or adherence to a ketogenic diet 5. Use of medication known to influence protein metabolism 6. Participation in a stable-isotope tracer study in the past 6 months 7. Tobacco/nicotine use 8. Undergoing exercise sessions more than 5 days/week. 9. Metal implants 10. Paralysis, limb loss, or congenital or acquired absence of skeletal muscle 11. Individuals with Phenylketonuria (PKU) 12. Dairy allergy or lactose intolerance