How does the body primarily obtain energy during periods of fasting?

During periods of fasting, the body primarily obtains energy by utilizing fat stores. When food intake is reduced or eliminated, the body needs to rely on its existing reservoirs of energy to maintain normal physiological functions.

Initially, the body may use available glycogen stores, which are carbohydrates stored in the liver and muscles. However, these glycogen stores are limited and can deplete quickly, typically within 24 hours of fasting. Once those stores are exhausted, the body shifts its energy production from carbohydrates to fats, initiating a process called lipolysis. During lipolysis, stored fats are broken down into free fatty acids and glycerol, which can be used as an energy source.

This shift to fat metabolism is essential for sustaining energy levels during prolonged periods of fasting. Fat stores provide a much larger energy reserve compared to glycogen, allowing the body to function effectively even when food is not consumed for an extended time.

In contrast, while protein can be used for energy and may be broken down during fasting if fat stores are insufficient, it is not the body's primary energy source; protein is more crucial for maintaining muscle mass and facilitating various biochemical processes. Burning carbohydrates exclusively would not be feasible during extended fasting, as glycogen stores will not last long enough