minimum of 3 days. Dietary guidelines of most
nutrients are intended to be intakes averaged
over at least 3 days and over several months for
those nutrients stored by the body, e.g. vitamin
A.
Physical activity levels, climate and other
factors can change dietary requirements. Anyone
who exercises and/or is exposed to cold or
hot environments may require different levels of
some nutrients as compared to levels listed in
current guidelines. As the reader evaluates
dietary assessments of physically active popula-
tions, these limitations of the dietary guidelines
should be considered.
Requirement for energy
Energy needs are related to body mass. In the
UK, median weights and heights of the popul-
ation, recorded in 1980, are used to calculate
energy needs (MJ · day–1). Total energy expendi-
ture (TEE) is expressed as a multiple of the basal
metabolic rate (BMR) and is affected by the
physical activity level. Examples of TEE calcula-
tions for men and women can be found in the UK
Report on Dietary Reference Values(Department of
Health 1991). Current US energy calculations are
based on median heights and weights found
in the second National Health and Nutrition
Examination Survey with empirically derived
418 special considerations
equations developed by the World Health
Organization (WHO 1985) specifically used to
estimate resting energy expenditure (REE). To
estimate total energy expenditure (TEE), REE is
multiplied by a factor that represents an activity
level which needs to be recorded over a suffi-
ciently long time accounting for weekdays
and weekends to increase validity of the estimate
of energy expenditure. Examples of this calcula-
tion can be found in the US reference (National
Research Council 1989).
Agreement regarding which equation to use
for TEE estimation does not exist. As published
in the WHO’s Report on Energy and Protein
Requirements, BMR forms the basis of the factorial
method to estimate TEE (WHO 1985). However,
examination of the calculations indicates that the
equations overestimate BMR of some population
groups (Piers et al.1997). Carpenter et al.(1995),
in a meta-analysis of 13 studies that utilized
doubly labelled water technique as the method
to measure TEE in free-living humans, con-
cluded that there are insufficient published
data to permit development of practical models
to predict TEE in adults.
Acknowledgement of potential limitations of
TEE calculations and of the derivation of energy
recommendations is necessary to prevent inap-
propriate energy-related conclusions made in
sports nutrition research or recommendationsFig. 31.1Performances of elite
female athletes have improved
rapidly with increased
opportunities for participation
and increased training loads.
Photo © Allsport / John Gichigi.