Which of the following metabolic events will not occur following 12-24 hour of fasting
**Core Concept**
The body's response to fasting involves a series of metabolic adaptations to maintain energy homeostasis. After an overnight fast, the body begins to mobilize stored energy sources, including glycogen, fatty acids, and ketone bodies.
**Why the Correct Answer is Right**
During the initial 12-24 hours of fasting, the body primarily utilizes stored glycogen in the liver and muscles for glucose production through glycogenolysis. This process is mediated by the enzyme glycogen phosphorylase, which breaks down glycogen into glucose-1-phosphate. However, after the initial glycogen stores are depleted, the body begins to rely more heavily on fatty acid oxidation for energy production. This is due to the increased activity of hormone-sensitive lipase, which mobilizes fatty acids from adipose tissue.
**Why Each Wrong Option is Incorrect**
**Option A:** Glycogen synthesis will not occur following 12-24 hours of fasting because the body is in a catabolic state, breaking down stored energy sources rather than synthesizing new ones.
**Option B:** Lipolysis will actually increase following 12-24 hours of fasting as the body attempts to mobilize fatty acids for energy production.
**Option C:** De novo lipogenesis, the process of synthesizing new fatty acids from glucose, is typically suppressed during fasting as the body prioritizes energy production from stored energy sources.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the body's metabolic response to fasting is highly adaptable, and the timing and extent of metabolic shifts can vary depending on individual factors such as age, sex, and nutritional status.
**Correct Answer: D. De novo lipogenesis**