During prolonged fasting, in what sequence are the following organic compounds used up by the body?
- First carbohydrates, next fats and lastly proteins
- First fats, next carbohydrates and lastly proteins
- First carbohydrates, next proteins and lastly lipids
- First proteins, next lipids and lastly carbohydrates
Answer
(1) First carbohydrates, next fats and lastly proteins
Solution
During fasting, the body first uses the readily available carbohydrates (blood glucose and the small glycogen reserve of liver and muscles).
⇒ When glycogen is exhausted, stored fats (adipose tissue) are broken down for energy.
⇒ Proteins (structural and functional molecules) are used only at the last, during starvation.
∴ Sequence: carbohydrates → fats → proteins.
Answer: (1)