Food and nutrition.pdf

90 Function of Foodwould also tend to be tired at the end of the day, and might well increasehis period of complete rest (at 1 kcal/min) by reducing the period of minoractivities. He would therefore have reduced his energy requirements to 2646 kcal, as shown in Table 15.This is just an example. In most in stanc,~s, when people increase theiroutput of energy, including work, they feel more hungry and increasetheir consumption of their staple food, be it rice, millet, maize wheat,cassava or anything else.The energy requirements of- ~ human being are affected by severalfactors. The important ones are:• Body size: A small person needs less energy than a large person.• Basal metabolic rate: BMR varies and can be affected by factorssuch as disease of the thyroid gland.• Activity: The more physical work or recreation performed, themore energy is required.• Pregnancy: A woman requires extra energy to develop the foetusand to carry its additional weight.• Lactation: The lactating mother needs additional energy toproduce energy-containing milk for the suckling baby. Therelatively long duration of breastfeeding among most Asians andAfricans results in a large proportion of women requiring extraenergy.• Age: Infants and children need more energy, for growth andactivity, than adults. In older persons, the need for energy issometimes reduced because there is a decline in activity andbecause their BMR is usually lower.• Climate: In warm climates, i.e. in most of the tropics andsubtropics, less energy is necessary to keep the body at its normaltemperature than in cold climates.Macronutrients: Carbohydrates, Fats and ProteinsCarbohydratesThe main source of energy for most Asians, Africans and LatinAmericans is carbohydrates in the food they eat. Carbohydrates constituteby far the greatest portion of their diet, as much as 80 per cent in somecases. In contrast, carbohydrates make up only 45 to 50 per cent of thediet of many people in industrialized countries.Carbohydrates are compounds containing carbon, hydrogen andoxygen in the proportions 6:12:6.They are burned during metabolism to produce energy, liberatingcarbon dioxide (C0 2) and water (H 20). The carbohydrates in the human