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| About our energy consumption | | |
Dr. Wahied Khawar Balwan
Energy is necessary for human beings to carry out routine physical work, maintain body temperature, body’s basal metabolism, build and replace body tissues, compensate for the excretory losses and allow physical activities.
Energy was traditionally been expressed as calories of kilocalories. Recently, the units of energy have been changed to kilojoules (4.184 kilojoules equal 1 kilocalorie). The energy value of a food item indicates its value to the body as a fuel. After the food is ingested, some of its energy may be ‘lost’ during digestion and metabolism. Although the energy value of some foods may be estimated by combustion in a bomb calorimeter where the macronutrients–fat, protein, carbohydrates and alcohol (ethanol) account for the energy Liberation. One joule is energy expended when 1 kilogram (kg) is moved 1 meter (m) by a force of 1 Newton (N). Approximately, 1 Calorie (kcal) equals 4.2 Joules (kJ) and 240 Calories (kcal) equal 1.0 megajoule (MJ).
The conversion efficiency of food energy into physical power depends on the form of energy source (type of food) and on the type of physical energy usage (e.g. which muscles are used, whether the muscle is used aerobically or anaerobically). The differing energy density of foods (fat, alcohols, carbohydrates and proteins) lies in their varying proportions of oxidizable carbon atoms. Release of energy from food follows transfer of electrons from carbon and hydrogen to carbon dioxide and water.
Swings in body temperature–either hotter or cooler—increase the metabolic rate, thus burning more energy. Prolonged exposure to extremely warm or very cold environments increases the Basal Metabolic Rate (BMR). People who live in these condition often have BMRs 5-20% higher than those in other climates. Physical activity also significantly increases body temperature which in turn uses more food energy. BMR is the number of calories your body burns at rest to maintain life. Instead, it is responsible for 60-70% of the calories expended through activities such as the beating of the heart, respiration, and body temperature maintenance.
Factors that affect BMR are as follows.
1. Genetics: This is one factor one cannot directly change. Some individuals have fast metabolisms while some others have slow metabolisms.
2. Gender: Due to greater muscle mass and lower body fat percentage, men have a 10-15% higher BMR than women.
3. Age: BMR of infants and younger children are more compared to adults.
4. Weight: Obese individuals have higher BMR values.
5. Height: Tall, thin people have a higher BMR values compared to short people of equal weight.
6. Fever: Fever increases the BMR. For every 10° F rise in body temperature, the BMR increases approximately 7%. Physical activity significantly increases body temperature.
7. External temperature: Prolonged exposure to extremely warm or very cold environments increases the BMR. People who live in these types of condition often have 5-20% higher BMR’s than those in other climates.
8. Endocrine function: Thyroid glands that produce too much thyroxin can double the BMR, while BMR can drop by 30-40% in individuals with hypothyroidism, or inadequate thyroxin production.
9. Exercise: In addition to increasing body temperature, exercise increases lean muscle mass, which burns more calories than fat–even when you’re not exercising.
REQUIREMENT OF ENERGY
The recommended daily energy allowanes shown in tables:
FACTOR AFFECTING THE ENERGY REQUIREMENT
Men engaged in light activity require 300 Kcal (1.2 MJ) less energy while very active individuals require 500 Kcal (2.1 MJ) more energy. The energy expended during walking varies greatly, depending upon the body weight and the speed of walking.
The survey conducted by National Monitoring Bureau (NNMB) revealed that in India nearly 50% of men and women suffer from chronic energy deficiency.
• Energy requirement of an individual is based on daily energy expenditure. As mentioned earlier it also dependent on age, body weight, level of physical activity, growth and physical status. In India, 70-80% of the total dietary calories are obtained from food grains such as cereals, millets, pulses and tubers.
• Children and adolescents obtain 55-60% of their daily requirement of calories from carbohydrates.
• Adolescent require more of energy for healthy growth. For example, girls and boys in the age group of 16-18 require 2060 kilocalories and 2640 Kcal, respectively.
• During pregnancy, additional energy is needed to support the growth of foetus and the health of pregnant women.
• Energy inadequacy leads to under-nutrition and at the same time excess intake results in obesity.
Common energy rich foods include cereals, millets, pulses, tubers, vegetable oils, ghee, butter, oil seeds, nuts, sugar, jaggery, etc. Coarse inexpensive cereals like jowar, bajra, and millets like ragi are also good sources of energy.
A number of processes go on to ensure the continuance of life without any conscious effort. These include the beating of heart, circulation of the blood, breathing, the regulation of body temperature, glandular activities etc. These process are known as the basal metabolic processes. The energy needed to keep these going is BMR which is measured as energy used there unit time cK.cal/ kg. hr.
Energy is also consumed by voluntary activities, which include work related to one’s occupation, profession or job, leisure activities such as reading, watching television, playing games, gardening, playing with children etc., and activities related to personal necessities, such as brushing teeth, bathing, eating, washing clothes, utensil etc.
Some energy is used to take the food into body, digest and carry the nutrients to the tissues and to eliminate waste. This is known as specific dynamic action of foods or the energy utilization.
Extra energy is needed during period of rapid growth for the building of tissues. These include pregnancy, early childhood and adolescence. The total energy need in pregnancy is estimated to be about 40,000 kilocalories. During lactation for secretion of milk mother need additional energy in the range of 700-1000 kilocalories per day. It has been observed that underfed mothers tend to have smaller babies, who have very little reserves of nutrients at birth. Inadequate food during infancy results in stunted growth. Continued increase in weight in adult after the age of 25, indicates intake of energy in excess of body needs.
Most people add weight after the age of 35 or 40 years, because they continue the energy intakes that they needed at the age of 25 years. But with age the energy needs decreased, due to the lowering of BMR. Most of the people became less active at this age. They can afford the luxuries of life such as eating rich and expensive foods. Thus there is an intake of excess food energy which is not utilized and is deposited as far in the body.
It is necessary to take adequate amount of energy, it you are obese, reduce energy intake to a level lower than one’s needs, to use up the deposited fat. Exercise in the form of active outdoor games, walking and indoor fitness exercise which will be helpful in weight reduction. But it must be accompanied by consistent, regular, carefully planned reduction of energy intake.
“Any error is this manuscript is silent testimony of the fact that it was a human effort” |
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