During long periods of fasting:

Correct option is A

Ans. (a) First of all, carbohydrates are used, then fats, and finally proteins are used.
Sol. During prolonged fasting, the body follows a specific sequence for energy utilization:
1. Carbohydrates (Glycogen Stores) – Initially, the body breaks down glycogen stored in the liver and muscles for energy. This lasts for 12–24 hours.
2. Fats (Lipids) – Once glycogen is depleted, the body shifts to fat metabolism, utilizing stored triglycerides for energy.
3. Proteins (Muscle Breakdown) – As fasting continues, the body starts breaking down muscle proteins to generate energy via gluconeogenesis, which can lead to severe muscle loss and organ damage.
Explanation of each option:
· (a) First of all, carbohydrates are used, then fats, and finally proteins are used. – Correct answer. The body first uses glycogen, then shifts to fat metabolism, and lastly breaks down proteins.
· (b) First of all, fat is used, then carbohydrates in the form of glycogen stored in the liver and muscles, and finally protein is used. – Incorrect, as carbohydrates (glycogen) are always used first, not fat.
· (c) First of all, lipids are used, then proteins, and finally carbohydrates are used. – Incorrect, as carbohydrates are always the body's first energy source.
· (d) None of the above. – Incorrect, as (a) correctly describes the process of energy utilization during fasting.