Info

aPAL ranges apply to both men and women. Reproduced with permission from FAO Human Energy Requirements. Food and Nutrition Technical Report Series No. 1. (2004) FAO, Rome.

aPAL ranges apply to both men and women. Reproduced with permission from FAO Human Energy Requirements. Food and Nutrition Technical Report Series No. 1. (2004) FAO, Rome.

unless his or her BMR is measured and account taken of his or her personal lifestyle (i.e., activity pattern). Nevertheless, the total energy expenditure of an individual child or adult is remarkably consistent from day to day, varying by only 1 or 2% provided that food intake and physical activity are meticulously standardized and account is taken in women of the stage of the menstrual cycle. The factors modulating BMR or the metabolic response to food are many, but their effect is small, so it is not surprising that energy expenditure is very predictable; the human body is thus a finely tuned and well-regulated machine. Abnormalities of regulation (e.g., in obesity) only arise because of a consistent discrepancy between the physiological controlled intake and expenditure, which, if discrepant by 1 or 2%, produces a 2- to 5-kg weight change in a year.

New measures of total energy expenditure estimated over 2 or 3 weeks can be obtained by using the double-labeled water technique, which relies on the difference in labeling of urine or saliva with the two heavy isotopes of water, deuterium and 18O. The differential dilution of 2H and 18O in urinary water is monitored over a 2- or 3-week period following a single oral dose of 2H218O. The 18O content is diluted more rapidly than the 2H because the oxygen in water exchanges rapidly with the body's bicarbonate pool, which turns over rapidly as carbon dioxide is produced by tissue metabolism. Thus, the difference in dilution rates of 18O and deuterium provides a measure of the rate of carbon dioxide production. The technique is expensive and difficult to perform analytically but very convenient for the subject being studied since only single daily or occasional urine or saliva specimens are needed during the period of observation.

This method is increasingly used, and together in children with a heart rate monitoring system, has been used to revise the estimates of population energy requirements. These are accurate for groups of people but not for individuals, who vary not only

Diet And Exercise Expertise

Diet And Exercise Expertise

Get All The Support And Guidance You Need To Be A Success At Dieting And Exercise. This Book Is One Of The Most Valuable Resources In The World When It Comes To Better Physical Personal Development Through Better Living.

Get My Free Ebook


Post a comment