How many kilocalories (kcal) of energy are yielded by carbohydrates upon metabolism?

RRB Nsg Superintendent -29 April 2025 (Shift-1st)

Applied Nutrition & Dietetics

Easy

Appeared in: RRB Nsg Superintendent -29 April 2025 (Shift-1st)

Explanation

Carbohydrates are a major macronutrient and the body's primary source of energy.
The physiological fuel value, or Atwater factor, for carbohydrates is 4 kilocalories (kcal) per gram.
This value represents the metabolizable energy that the body can actually derive from the food after digestion and absorption.
Glucose, a simple carbohydrate, is the main fuel for most cells, particularly for the brain, which relies almost exclusively on it for energy.

Option A: 9 kcal per gram is the energy yield for fats (lipids), not carbohydrates. Fats are the most energy-dense macronutrient.
Option B: 2 kcal per gram is the approximate energy yield for dietary fiber, which is a type of carbohydrate that is fermented by gut bacteria rather than being fully digested and absorbed like other carbohydrates.
Option C: 5 kcal per gram is not the standard physiological fuel value for any of the major macronutrients. While some laboratory methods like bomb calorimetry might yield slightly different values, 4 kcal/g is the accepted standard for carbohydrates in human nutrition.

Visual 1: Infographic: A comparative chart showing the caloric content per gram for carbohydrates (4 kcal), proteins (4 kcal), and fats (9 kcal). The chart could use simple bar graphs for easy visual comparison.
Visual 2: Diagram: A simple flowchart illustrating the metabolic pathway of carbohydrates starting from ingestion to the production of ATP (energy), highlighting that 1 gram yields 4 kcal.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological fuel value of carbohydrates as background academic context rather than a clinical decision trigger.
Nutritional Assessment: Nurses must know these values to calculate patients' daily caloric intake and expenditure, which is crucial for creating diet plans for weight management, diabetes control, and post-operative recovery.
Patient Education: This knowledge is essential for educating patients about balanced diets, reading food labels, and understanding the energy content of different food groups.
Total Parenteral Nutrition (TPN): When calculating TPN formulas, nurses and dietitians use these values to ensure critically ill patients receive adequate caloric intake to prevent malnutrition and support healing.

How to Approach the Question

Identify the core question: The question asks for the specific energy yield (in kcal) of carbohydrates.
Recognize this as a factual recall question common in nutrition and biochemistry.
Recall the standard physiological fuel values (Atwater factors) for the three main macronutrients.
Remember: Carbohydrates = 4 kcal/g, Proteins = 4 kcal/g, and Fats = 9 kcal/g.
Compare the recalled value for carbohydrates (4 kcal/g) with the given options.
Select the option that matches the correct value.

Concept Tested & Keywords

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