Food and nutrition.pdf

88 Function of FoodBMR varies from individual to individual. Important general factorsinfluencing BMR are the person's weight, gender, age and state of health.BMR is also influenced by the person's body composition, for examplethe amounts of muscle and adipose tissue and therefore the amounts ofprotein and fat in the body.In broad terms, bigger people with more muscle and larger bodyorgans have higher BMR than smaller people.Elderly people tend to have lower BMR than they had when theywere young, and females tend to have lower BMR than males even on aper kilogram body weight basis. There are exceptions, however, to all thesegeneraliza tions.BMR is important as a component of energy requirements. Table 10shows BMR of adult men and women according to height and weight,both per kilogram body weight and as total energy per day.The table shows, for example, that in females aged 30 to 60 years BMRranges from 1 190 to 1 420 kcal per day.This is the amount of energy required by a woman at complete restfor 2,~ hours. Of course many adult females in developing countries aresmaller than 1.4 m in height and 41 kg in weight; their BMR might thenbe a little lower than 1 190 kcal per day.Energy RequirementsThe mean daily energy requirements of adult men and women doingwork classified as light, moderate and heavy are given in table, expressedas multiples of BMR.The table shows, for example, that a woman doing heavy workrequires energy equal to 1.32 times her BMR. If the woman is aged 25years, is 1.4 m tall and weighs 41 kg, according to Table her BMR wouldbe 1100 kcal per day. Thus her daily requirements are: 1100 kcal x 1.32 =2002 kcal.It is often useful to estimate energy needs for various activities that aperson may do for particular lengths of time.The energy expenditure is usually calculated by multiplying anactivity factor or metabolic constant, which varies according to the activity,by the individual's BMR.Table gives the activity factors for calculating gross energyexpenditure of various activities for adult males and females.The average human burns energy at his or her BMR only when atcomplete rest. All ordinary movements require additional energy, andphysical work, of course, requires more still. For a healthy male with BMRof 1 kcal/min, an average day may involve the energy expenditure shownin Table.