Body Comp Flashcards
why is body comp assessment relevant to dieticians?
nutrition diagnosis, help guide intervention development, monitor impact of nutrition interventions
3 components of study of body comp:
rules and models, bio influences, measurement techniques
what are the 5 lvls of human body comp?
atomic, molecular, cellular, tissue-system, whole body
subcomponents of level 4
blood, bone, adipose, skeletal muscle, other
basic 2 compartment model:
fat and fat free mass
key observations about men in Behnke’s reference man and woman:
generally > ht and wt and muscle mass, < total body fat
what is essential fat?
fat in internal organs (heart, lungs, liver, spleen, muscles, intestines, kidneys) bone marrow, CNS, cell membranes ; in females there is also sex specific essential fat; essential for normal physiological functioning
what is storage fat?
includes fat primarily in adipose tissue deports, fat that surrounds/protects organs (visceral), adipose tissue depot beneath skin’s surface (subcutaneous)
what is fat free mass?
body mass devoid of all extractable fat (muscle, connective tissue, water, organic matter, mineral content); ie. FFM = body mass - fat mass
what is lean body mass?
FFM + essential fat
direct methods to assess body comp:
cadaver analysis (direct chemical analysis of the adult body, most accurate) which is the gold standard but not practical
indirect methods (in vivo) to assess body comp:
anthropometry, hydrodensitrometry, air displacement plethysmography, whole body counting, BIA, DXA, CT, MRI, ultrasound
error associate with in vivo methods:
methodological (data collection) error, error in assumptions (calculations)
how close measured value gets to true value
validity
how close measured values are to each other
reliability
bio factors that influence body comp:
genetic influences, life stage/age, exercise, chronic disease
LBM ___ throughout childhood and ____ with ^ age
increases; decreases
anthropometric measures:
wt, skinfold, circumferences, stature, limb lengths, breadths
anthropometric findings compared to:
reference standards and previous measurements of individual
uses of anthropometry?
estimate body comp, evaluate nutrition status, indices and ratios can predict disease risk
ht is measured to the nearest ___ cm
0.5
primary method for height:
stadiometer
estimates for height:
knee height index, half arm span, Demi arm span, ulna length, recumbent length with measuring tape
knee height best measured using _____
sliding knee ht caliper
what is half arm span?
distance form midline at sternal notch to tip of mid finger while non dominant arm is stretched out horizontally (ht calculated by doubling this measure)
what is demispan?
distance from midline at sternal notch to web between mid and ring fingers along outstretched non dominant arm (gender specific formulas)
equations used to predict height in men and women >65 years:
ulna length (olecranon process at elbow to midpoint of styloid process at wrist)
wt is measured to nearest ____
0.1 kg
relationship between BMI and mortality represented by ____
J shaped curve
risk of death is lowest at this BMI range:
22.5-25
wt measurement at time of exam is called:
actual body weight
clinical presentation to consider in context of interpretation of ABW:
fluid status, disease burden, tumours
what is IBW?
ideal weight associated with max life expectancy for given ht
frame size measurement includes:
biacromial breadth, bitrochanteric breadth, ratio of stature to wrist circumference, breadth of chest, knee and wrist breadth, elbow breadth
most accessible and easy to measure, practical frame size measurement?
elbow breadth
frame size limitations:
subjective, reference data not representative of entire population, quality of data variable, inadequate control of confounding variable that can influence wt, unclear how frame size was determined , don’t provide info on body comp
calculating IBW use ____ equation
Hamwi
how to calculate %IBW?
actual body weight / ideal body weight x 100
how to calculate IBW?
use BMI target
used by some RDs for obese pt when calculating energy requirements
adjusted body weight
premise of AdBW is ____ and assumption is _____
adipose tissue not as metabolically active asleep tissue so ABW in equations to predict BEE may result in overestimation ; 25% of excess wt in obese person is metabolically active
equation for AdBW?
0.25 (ABW - IBW) + IBW
AdBW typically used when client > ____% IBW
125-130
%UBW is calculated by:
actual / usual weight
calculate %wt lost:
(usual-current) / usual x 100
estimated IBW for amputees:
((100 - %amputation) / 100) x IBW for original ht
android type also referred to as ____ and is _____
apple/male type; > proportion fat distributed in upper body, esp. abdomen
gyroid type also referred to as ____ and is _____
pear/female type; > proportion fat distributed in lower body, esp. hips and thighs
excess ab fat is associated with:
insulin resistance/hyperinsulinemia, prediabetes, hypertension, hyperlipidemia, stroke, mortality
cut points for WHR (waist to hip ratio)
0.95 for M, 0.80 for F
better predictor of overall ab obesity than WHR
waist circumference
WC outpoints to determine disease risk:
> /= 102 cm for M, >/=88 cm for F
skin folds measurement is based on this assumption:
direct relationship exists between total body fat and subcutaneous fat
2 uses for measurements of skinfolds collected:
1) scores for various measures added and sum used to indicate relative degree of fatness 2) scores inputted into various math regression equations developed to calculate %BF
assumptions involved in skin folds:
1) double thickness of skin/subcutanoues adipose tissue has constant compressibility 2) thickness of skin is negligible or a constant fraction of skin fold 3) thickness of SAT is constant/predictable within and between individuals 4) fat content of adipose tissue is constant 5) proportion of internal to external fat is constant 6) body fat is normally distributed
which has more impact, absolute change or percentage change?
%change
4 common skin fold measurement:
bicep, tricep, sub scapular, suprailiac
advantages of skin folds:
inexpensive, require little space, expedient, estimates of body comp correlate well with those done from hydrostatic weighing when skin folds done correctly
limitations of skin folds?
requires extensive training, less accurate than other indirect methods
general procedure of estimating body comp from body density
densitometry
density of human body is ration of ____ and ___
mass (MA) ; volume (v)
equation for body density:
Db = MA/V
synonymous with hydrodensitometry, original gold standard of body comp assessment prior to advancement of other tech
underwater weighing
modern alternative air displacement plethysmography
bod pod and pea pod
technique of hydrodensitometry is based on:
archimedes Principle: volume of object submerged in water = volume of water the object displaces
how does UWW work?
computes body volume as diff between body mass measured in air (Wa) and body weight measurement during water submersion (Ww); body volume (BV) is = to the loss of wt in water with the appropriate temp correction for water’s density (Dw)
equation for UWW:
BV = (Wa-Ww) Dw
UWW procedure:
subject exhales fully, slowly lean forward until head completely submerged, try press as much air from lungs as possible, stays motionless, multiple trials
factors that affect UWW measurements?
consumption of food and carbonated beverages beforehand, fluid losses during training, fluid retention prior to menstruation, ability to forcibly exhale while submerged
corrections required for UWW:
residual volume (RV) , volume of gas in GIT (VGI)
how to calculate body density using UWW?
Db = Wa / ((Wa-Ww)/Dw - (RV+VGI))
equations used for calculate %BF?
siri equation, brozek equation
assumptions of FFM for UWW?
FFM has constant lvl of hydration and constant proportion of bone mineral to muscle
density of fat is ____ and FFM is _____
0.9007g/cm^3; 1.100 g/cm^3
limits of density assumptions for FM and FFM?
represent averages for young and middle aged adults, constants vary among individuals and groups (ie. race/ethnicity)
how to convert %BF into fat mass?
TBW x (%fat/100)
biggest source of error in UWW?
residual volume
limitations to UWW?
requires considerable subject cooperation and training, special equipment / space required, evaluator requires training, assumption of constant density of FFM, gas trapped in GIT can only be estimated
technique where body vol and density estimated using pressure-volume relationships
air displacement plethysmography
bod pod need to adjust for:
isothermal effects (put on swim cap and suit)
total body volume is corrected for ____
thoracic gas volume (measured or predicted)
TGV measured is better than predicted for this population:
athletes at extreme heights, >185cm
final body volume is corrected for:
TGV and body surface area
advantages of ADP?
validation studies show good agreement with other criterion methods, expedient, easy test to perform, more suitable for children and elderly v UWW
limitations of BOD POD?
expensive, not portable , depend on assumption that FFM has constant density
