The purpose of the study is to see if a ketogenic diet compared to a standard diet is better to maintain muscle function and health in hospital admitted pneumonia patients.

Bacterial community-acquired pneumonia (CAP) is a leading cause of hospitalization and mortality in older adults, often resulting in significant muscle wasting, systemic inflammation, and microbiome dysbiosis. Muscle loss, driven by bedrest, acute illness, and antibiotic-induced dysbiosis, all contribute to prolonged hospital stay, delayed recovery, and long-term physical decline. Current interventions such as physical rehabilitation and increased protein intake are largely ineffective in mitigating the acute illness-induced muscle wasting due to metabolic dysfunction such as impaired glucose control. Preliminary evidence suggests that ketogenic enteral feeding is safe, reduces inflammation, stabilizes metabolism and preserves functional outcomes in hospitalized patients. Because most of older hospitalized CAP patients are able to ingest food orally, our study aims to test the safety, feasibility and determine effect sizes for preliminary evidence of a 10-day oral ketogenic diet (low carbohydrate, high fat) in older CAP patients.

The investigators will conduct a double-blinded pilot randomized clinical trial in 30 hospitalized older adults (>55 years) with bacterial CAP, randomizing participants to a ketogenic feeding (n=15) or standard hospital feeding (n=15). Muscle mass will be assessed using ultrasound, inflammatory and metabolic biomarkers from blood, and microbiome composition from oral and skin swabs collected at baseline, 10-Day post-intervention, and 1-month post-intervention follow-up. Handgrip strength will be collected at baseline and 10-day follow-up. Physical activity measures (accelerometry) will be measured for 7 days after the 10-day and 1-month follow-up visits. Physical function (short physical performance battery), handgrip strength, and activity levels (accelerometry) will be measured at 1-month follow-up. Daily blood ketone level measurements will guide feeding adjustments to maintain ketosis, and dietary habits will be assessed weekly post-intervention until 1-month follow-up. Meals for the 10-day intervention will be prepared in a metabolic kitchen by a clinical nutritionist.

If successful, this study will provide evidence for oral ketogenic feeding as an innovative intervention to prevent muscle wasting and functional decline, supporting a future phase IIb clinical trial targeting middle-aged and older adults hospitalized with CAP.

Inclusion Criteria:

• Age 55 years and older
• Bacterial community-acquired pneumonia
• Expected at least 10-day stay in the hospital
• Ability to ingest food orally
• Willingness to be randomized to either treatment group
• Willingness to participate in all study procedures

Exclusion Criteria:

• Failure to provide informed consent
• Moribund
• Vegetarian/vegan
• Severe cardiac disease, including NYHA Class III or IV congestive heart failure, clinically significant aortic stenosis, history of cardiac arrest, use of a cardiac defibrillator, or uncontrolled angina
• Diagnosed dementia
• Hip fracture, hip or knee replacement, or spinal surgery within past 4 months
• Simultaneous participation in another intervention trial