Impact of Time Restricted Feeding on Daily Protein Requirements

The investigators aim to assess 24-hour protein kinetics at two different levels of protein intake: 0.8 (RDA) and 1.6g/kg/day (2RDA) during a normal dietary (TRAD) and a time restricted feeding (TRF) pattern in older adults. Individuals in the TRF pattern will only consume food during a 6-hour eating period and fast for the remaining 18 hours. Individuals in the TRAD pattern will consume isocaloric and isonitrogenous (RDA or 2RDA) diet but consume an all-beef-breakfast. Participants will consume oral stable isotopes to measure muscle protein synthesis (MPS), whole-body muscle protein breakdown (MPB), and whole-body protein balance (WBPB). Appropriate muscle, blood samples, and urine will be collected throughout a 24-hour metabolic trial following a 2-day controlled diet.

Inclusion criteria

• Men and women ages 50-75 years.
• BMI 20-30 kg/m2 inclusive.
• Capable of providing informed consent.
• COVID-19 negative and/or asymptomatic

Exclusion criteria

• Subject who does not/will not eat animal protein sources.
• Body mass index <20 or >30.
• Hemoglobin <10g/dL at screening.
• Platelets <150,000/uL at screening.
• History of diabetes.
• History of chemotherapy or radiation therapy for cancer in the 6 months prior to enrollment.
• History of gastrointestinal bypass/reduction surgery.
• History of a chronic inflammatory disease (e.g. what?)
• Currently receiving androgen (e.g., testosterone) or anabolic (e.g., GH, IGF-I) therapy.
• Currently using prescription blood thinning medications.
• Currently using corticosteroid medications.
• Unable or unwilling to suspend aspirin use for 7 days prior to Visit 3.
• Unwilling to avoid using protein or amino-acid supplements during participation.
• Subjects who are unwilling to fast overnight.
• Participating in >200 minutes/week of vigorous exercise and/or >4 days/week of resistance training.