http://www.mayoclinic.com/health/calcium-supplements/
AN00420>
Medline Plus. ‘‘Calcium.’’ U. S. National Library of Medi-
cine, March 14, 2007.<http://www.nlm.nih/gov/
medlineplus/calcium.html>
Office of Dietary Supplements. ‘‘Dietary Supplement Fact
Sheet: Calcium.’’ National Institutes of Health, Sep-
tember 23, 2005.<http://ods.od.nih.gov/factsheets/
calcuim.asp>
National Institute of Arthritis and Musculoskeletal and Skin
Diseases (NIAMS). ‘‘Calcium Supplements: What to
Look For.’’ NIAMS, April 2005.<http://www.niams.
nih.gov/bone/hi/calcium_supp.htm>Tish Davidson, A.M.Calorie restriction
Definition
The definition of calorie restriction is when the
body does not receive an adequate intake of energy.
This can result as a consequence of lack of availability
of adequate volumes of food. However, sometimes the
failure to consume an adequate calorie intake may be a
conscious and deliberate decision, for example, in
individuals seeking to lose weight or people who suffer
with the eating disorder,anorexia nervosa. Calorie
restriction can result in malnutrition or a deficiency
of one or more nutrients.Purpose
The human body requires an adequate amount of
energy or calories to enable us to grow, perform daily
activities, produce hormones and to minimize the risk of
nutrition-related complications. Calorie requirements
for individuals vary from one individual to the next
and are dependent on variables including gender, age,
activity levels, climate and environment and the presence
or absence of medical or nutritional complications. Con-
sequently, it is possible that individuals of similar weight
and age may have different energy requirements owing
to unique individual needs. In addition to the body
requiring energy to perform the aforementioned tasks,
energy is also required to support activity of the internal
organs and to maintain body temperature. This energy is
called the basal or restingmetabolism. The basal meta-
bolic rate (BMR) is determined experimentally when an
individual is lying down at complete physical and mental
rest under standardized environmental conditions.
Research over many years has provided researcherswith guidelines on how to assess and determine an indi-
viduals BMR using specific calculations.DescriptionIndividuals require a certain number of calories
on a daily basis, which incidentally may vary subject to
activity levels and physical status but overall is within
a relatively stable range. When dietary intake remains
stable weight too remains unchanged. Conversely,
increases or decreases in intake can result in weight
changes. To clarify,
When energy intake equals energy expenditure,
weight remains unchanged.
When energy intake exceeds expenditure, weight
increases.
When energy intake is less than expenditure, weight
will decrease.
It is when expenditure exceeds calorie intake that
the body experiences a negative energy balance and
weight loss ensues.
There is little research available to help us under-
stand the impact of starvation on humans. Under-
standably, ethically it would not be appropriate to
impose such situations on individuals, however, two
major studies did impose such situations in 1919 andEstimated daily calorie needsCalorie range
Sedentary Active
Children
2–3 years 1,000 1,400
Females
4–8 years 1,200 1,800
9–13 1,600 2,200
14–18 1,800 2,400
19–30 2,000 2,400
31–50 1,800 2,200
51 1,600 2,200
Males
4–8 years 1,400 2,000
9–13 1,800 2,600
14–18 2,200 3,200
19–30 2,400 3,000
31–50 2,200 3,000
51 2,000 2,800
Sedentary means a lifestyle that includes only the light physical activity
associated with typical day-to-day life.
Active means a lifestyle that includes physical activity equivalent to walking
more than 3 miles per day at 3 to 4 miles per hour, in addition to the light
physical activity associated with typical day-to-day life.
SOURCE: Center for Nutrition Policy and Promotion, U.S.
Department of Agriculture(Illustration by GGS Information Services/Thomson Gale.)Calorie restriction