Evaluate the following dietary prescription for a malnourished elderly patient: 'Limit carbohydrates to <20% of energy and increase fat to 60% to promote ketone-mediated brain fuel and reduce appetite.' Is this appropriate? Justify your answer.

• A. Not appropriate: In malnourished elderly patients, extreme carbohydrate restriction may increase gluconeogenesis and protein catabolism, risking muscle loss and impaired immune/repair functions; while ketones can supply some brain fuel, adequate carbohydrates are important to spare protein and maintain health.
• B. Appropriate only if protein intake is eliminated so that all dietary amino acids are prevented from contributing to gluconeogenesis, thereby preserving muscle mass directly.
• C. Perfectly appropriate: elderly individuals universally benefit from very low carbohydrate intake as ketones fully replace glucose and completely protect against muscle loss, making it ideal for malnourished patients.
• D. Appropriate only if the patient has type 1 diabetes, otherwise it will have no metabolic effect and can be followed without monitoring.

Answer: (A)