5.4 Energy in Food Ingredients

• Nutritional Energy: Food provides both nutrition and energy. Not all nutrients give energy, however. Only proteins, carbohydrates, and fats provide energy. The other nutrients do not.

• Muscle Energy: Muscles help with movement (e.g., walking, running, sitting). Energy consumption depends on muscle contraction and relaxation. More muscle activity requires more energy.

• Energy at Rest: Even when we do not move, we still require energy. This happens because even while resting, muscles involved in respiration and heart functions continue to work. This energy is referred to as basic metabolic energy. It is used for essential functions like breathing, maintaining body temperature, and heartbeat.

• Factors Influencing Energy Needs:

1. Basic Metabolic Rate (BMR): The energy needed for basic bodily functions at rest.

2. Type of Physical Activity: The energy needed increases with physical labor or exercise.

3. Influence of Food: The type and amount of food influence energy requirements.

• Additional factors such as growth, physical condition, and climate can also affect energy needs.

5.4.1 Standard Unit to Calculate Food Energy

• Energy from Food: The energy from food is primarily heat energy, and the standard unit used to measure it is the calorie.

• Kilocalorie: In nutrition, the term “calorie” is often used to refer to a kilocalorie (kcal), which equals the energy needed to raise the temperature of 1 kilogram (1000 grams) of water by 1°C.

1 kilocalorie = 1000 calories

• Kilojoule: According to international standards, kilojoule (kJ) is used instead of kilocalorie. The conversion is as follows:

1 food calorie (kilocalorie) ≈ 4.2 kilojoules

5.4.2 Determining Food Energy in Food Nutrients

• Nutrient Diversity in Food: Foods can be categorized into mixed or single nutrients.

• Mixed foods (e.g., milk, eggs, khichuri, guava) contain more than one nutrient.

• Single foods (e.g., sugar, glucose) contain only one nutrient (e.g., carbohydrates).

• Nutrient Composition: To calculate the energy content, it’s essential to know which nutrients are present and in what amounts. This information is found in food value charts.

• Calorie Calculation: The calorie values of carbohydrates, proteins, and fats are:

• Carbohydrate: 4 calories per gram

• Protein: 4 calories per gram

• Fat: 9 calories per gram

Vitamins, minerals, and water are not considered in calorie calculations as they do not provide significant energy.

Example Calculation:

Given 20 gm of chira, the nutritional breakdown is as follows:

• Carbohydrate: 15.4 gm (77%)

• Protein: 1.32 gm (6.6%)

• Fat: 0.24 gm (1.2%)

To calculate the calories:

• From 15.4 gm carbohydrate: 15.4 × 4 = 61.6 food calories

• From 1.32 gm protein: 1.32 × 4 = 5.28 food calories

• From 0.24 gm fat: 0.24 × 9 = 2.16 food calories

Total for 20 gm of chira:

• 69.04 food calories (or 69.04 kilocalories)

For 1 kg (1000 gm) of chira:

• (69.04 × 1000) / 20 = 3452 food calories or 3452 kilocalories

Converted to kilojoules:

• 3452 kilocalories × 4.2 = 14,490 kilojoules (approx.)

Energy Requirements

• Adult Energy Needs: The average adult requires about 2000 to 2500 food calories daily. However, this depends on factors like gender, physical activity, and health condition.

• If a person consumes more calories than needed, the excess is stored in the body as fat.