ENERGY AND PHYSICAL ACTIVITY

     Whether a man eats for living or lives for eating, food is his prime concern. Nutrition significantly  promotes man's developoment, his health and welfare. The subject nutrition, perhaps, is the most controversial. This is due to the fact that nutrition is concerned with food and everyone feels compeent enough to talk like an expert on nutriton. 

ENERGY SUPPLY

Food is the fuel source of the body. The ingested food undergoes metabolism to liberate energy required for the vital activities of the body. 

Energy content of foods:
The calorific value (energy content) of a food is calculated from the heat released by the total combustion of food. Calorific values of foodstuffs is given here:

Foodstuff	Energy value (Cal/g) in the body
Carbohydrate	4
Fat	9
Protein	4

It must be noted that the nutrients, namely vitamins and minerals, have no calorific value, although they are involved in several important body functions, including the generation of energy from carbohydrates, fats and proteins.

PHYSICAL ACTIVITY OF THE BODY

The physical activity of the individual is highly variable. The amount of energy needed for this depends mainly on the duration and intensity of muscular activity. For the sake of convenience, the individuals are classified into different categories with regard to their physical activity and the requirement of energy:

• Sedentary work
• Moderate work
• Heavy work
• Very heavy work

Classification of activities based on occupation

Sedentary
Male

Teacher, Tailor, Barber, Executives, Shoemaker, Priest,, Retired personnel, Land-Lord, Peon, Postman etc

Female

Teacher, Tailor, Executives, Housewives, Nurses etc

Moderate
Male
          Fisherman, Basket-maker, Potter, Goldsmith, Agricultural labour, Carpenter, Mason,    Electrician, Fitter, Turner, welder, industrial labourer, cooli, weaver, driver,  etc

Female

Servant-maid, cooli, basket-maker, weaver, agricultural labourer, beedi-maker etc

Heavy
Male

Stone-cutter, blacksmith, mine worker, woodcutter, gang-man, sportsmen etc

Female

stone-cutter, mine worker,  sports women etc

Very heavy work

construction workers, rikshaw pullers, bodybuilders, olympic athlets etc

Energy requirements of an adult individual

The daily requirements of energy is rather variable which depends on basal metabolic rate, inturn depends on age,sex, body size etc and physical activity. As per some rough calculation, caloric requirements of an adult per day (kcal/day) is in the following ranges:

• Light work:                  2200-2500
• Moderate work:          2500-2900
• Heavy work:                2900-3500
• Very heavy work:       3500-4000

The expenditure of energy for some physical activities:

PHYSICAL ACTIVY	ENERGY REQUIREMENT (kcal/hr)
Sitting (quietly)	25
Standing (quietly)	30
Writing/eating/reading	30
Car driving	60
Typing	75
Household work	80
Slow walking	130
Sexual intercourse	140
Cycling slow	150
Moderate running	500
Swimming	600
Walking upstairs	800

 


References: 1. Biochemistry - U. Satyanarayana, 2nd Edition
                      2. Nutritive Value of Indian Foods - National Institute of Nutrition