Design a short explanation integrating ketosis, gluconeogenesis, and protein sparing to predict physiological changes during the first two weeks of a very-low-carbohydrate (keto) diet in a healthy adult.

• A. Glycogen stores are immediately replenished, protein synthesis skyrockets so no amino acids are used, and ketone production drops to zero, resulting in no metabolic adaptation.
• B. Initially glycogen stores are used and gluconeogenesis increases using amino acids, leading to some protein catabolism; as ketone production rises (ketosis) the brain uses ketones reducing but not eliminating glucose demand, which spares proteins over time though some continued protein turnover and mild ketone-induced acid buffering adjustments occur.
• C. The body converts all dietary and stored fats into glucose directly, stopping gluconeogenesis entirely and causing protein stores to be completely preserved without ketone formation.
• D. The immune system is completely shut down in the first 48 hours, eliminating the need for proteins as antibodies, and therefore proteins are never catabolized on such diets.

Answer: (B)