**Core Concept**
The acute catabolic phase is a critical period following major surgery, characterized by a surge in stress hormones, such as cortisol and catecholamines, which stimulate the breakdown of muscle protein and lipolysis. This phase is marked by a negative nitrogen balance, where the body's demand for amino acids exceeds its ability to synthesize them.

**Why the Correct Answer is Right**
The acute catabolic phase typically lasts for 3-5 days after surgery, during which the body's energy expenditure increases, and muscle protein synthesis is suppressed. This period is characterized by increased levels of cortisol, which inhibits protein synthesis and stimulates the breakdown of muscle protein. The body's response to surgery triggers the release of various hormones, including insulin-like growth factor-1 (IGF-1), which helps regulate protein metabolism.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because the acute catabolic phase typically lasts longer than 1-2 days, which is the initial response to surgery.
* **Option B:** Incorrect because the anabolic phase is the period of recovery, where the body rebuilds muscle protein and restores its energy stores, whereas the acute catabolic phase is a period of breakdown.
* **Option D:** Incorrect because the hypermetabolic phase, also known as the hypercatabolic phase, is a more severe and prolonged response to severe injury or infection, lasting for weeks or even months.

**Clinical Pearl / High-Yield Fact**
The acute catabolic phase is a critical period for nutritional support, and adequate caloric and protein intake are essential to prevent muscle wasting and support wound healing.

**Correct Answer:** C. 3-5 days