Understanding Energy Needs and Malnutrition: A Comprehensive Guide

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17. Differentiation of energy needs. Resting energy expenditure. Thermic effect of food. Thermic effect of exercise. The world fatigue problem of hunger, general signs of marasmus


  • - Energy in humans is obtained in the form of food:

  • - It is vital for the human body and without it the body would break down

  • - Energy is expressed in calories or joules: 1 Kcal = 4.19 KJ

  • - Energy needs are met by 3 basic nutrients: proteins, fats and carbohydrates.

  • - Energy is required for:

o Resting energy expenditure: amount of calories required for a 24-hour period by the body during resting conditions (basal metabolism).

 The values change with sex, age, height and weight and are calculated by the Harris Benedict equations. o Energy required for the specific dynamic action of food
o Energy for thermogenesis: accounts for 75% of energy loss
o Energy for activities

  • - Energy requirement depends on: physical activity, body size/composition, size, climate and the environment

  • - Our body requires a certain number of calories to function which are burned in three main ways:

o To sustain bodily functions (staying warm, breathing, having your heart beat, etc) → This is called Basal Metabolic Rate (BMR) o To perform activity (daily living, work and exercise) → This is called the Thermic Effect of Exercise (TEE)
o To extract energy and nutrients from food (digest, absorb and process chemically) → This is the Thermic Effect of Food (TEF)

Thermic Effect of Food:

  • - The TEF is the increase in energy expenditure above resting metabolic rate due to the cost of processing food for storage or use.

  • - It accounts for 10% of caloric intake but varies with different foods, as for e.g.:

o Fats are easily processed → low thermic effect
o Proteins are difficult to process → high thermic effect

Thermic Effect of Exercise:

- The TEE refers to the calories you burn when you perform any type of physical activities, as: o Work-related activities such as vacuuming cleaning, washing the car,
o Transportation (walking or climbing stairs), and
o Recreational (golfing, swimming or dancing

  • - Heat is released when you burn calories, which is why you feel hot when you exercise

  • - ± 30% of the calories you need in a day are used for TEE

  • - The calories you burn through activity are related to your amount of muscle.

o Muscles allow you to work harder, which burns more calories and, in turn, builds more muscle - a never-ending cycle.

o If you are trying to lose weight or maintain weight loss, increase your physical activity - Nutritional requirements for athletes have 2 components:

o Quantitative (energy value of their diet)

o Qualitative (nutritional value of their diet: proteins, fats, carbs, vitamins, minerals, water) - Energy requirement depends on:

o Type/ Period of activity o Rate of activity
o State of training

o Other energy expenditures during the day

o Gender
- Sports activities averaging approx. 2 hours, depending on how vigorous require:

o 500-1000 Kcal (high)
o 1000-1500 Kcal (moderately strenuous) o 1500-2500 Kcal (strenuous)


  • - Inadequate intake/absorption/metabolism of energy supplies

  • - A person is malnourished when:


o Unintentional weight loss of >10% of BW in the preceding 3 months o BW less than 90% of the ideal amount corresponding to their height o BMI < 18.5
o Severe malnutrition is BW < 70%

o Incompatible with life <60%

  • - Is a form of severe malnutrition characterized by energy deficiency

  • - Extensive tissue and muscle wasting

o Body weight is reduced to less than 60% of the normal (expected) body weight for the age

  • - Variable edema

  • - Other common characteristics include – dry skin, loose skin folds hanging over the buttocks and axillae, etc.

  • - There is also drastic loss of adipose tissue from normal areas of fat deposits like buttocks and thighs

  • - The afflicted are often fretful, irritable, and voraciously hungry

  • - It can be distinguished from kwashiorkor in that the latter is protein deficiency with adequate energy intake whereas the former is inadequate energy intake in all forms, including protein


  • - It is a form of severe protein–energy malnutrition with sufficient calorie intake, but insufficient protein consumption

  • - Common in areas of famine or poor food supply

  • - Characterized by edema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates

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