Lecture 2 Flashcards
What is body composition
-refers to the components that make up the body
What is included in body composition
-body weight and relative amounts of muscle, fat, bone, and other vital tissues
-often limited to fat and lean body mass
What is relative body mass
-percentage of fat
What is absolute body mass
-kilograms of fat
What is a good body fat percentage for males
-12-23%
What is a good body fat percentage for females
-17-26%
What health risks is obesity related to
-cardiovascular disease
-peripheral vascular disease
-hypertension
-type 2 diabetes
-metabolic syndrome
-sleep disorders
-stroke
Why do we measure body composition
-determine risk of metabolic diseases
-maximize performance/health
-research outcome
Different types of body composition models
-two component models
-three component models
Two component models
-anthropometry (circumference)
-skinfolds
-bioelectrical impedance analysis
-underwater weighing
-bod pod
-ultrasound
Three component models
-duel energy x ray absorptiometry (DEXA)
-MRI
-CT
When is a body composition technique valid
-when it measures what it says it measures
When is a body composition technique considered reliable
-when the results are reproducible
What is considered the gold standard for body composition measurements
-DEXA
-3 component model which provides an estimate of bone, fat, and lean tissue densities
How does underwater weighing work
-one of the most valid methods of estimating relative body fat
-uses density
What is air-displacement plethysmography
-BOD POD
-displacement of air in a sealed compartment
What is BMI
-proxy measure for body fat
-used to classify underweight, normal, overweight, and obesity classes in adults and children
What is the equation for BMI
BMI = wt (kg) /Ht2 (m2)
What are the strengths of BMI
-simple, inexpensive, reliable measure
-national and international standards available
-high specificity for detecting excessive adiposity with higher BMI values in adults
Weaknesses of BMI
-does not provide direct body fat measure
-poor estimates of body fat in some ethnic groups, ages, body build/frame size
What does waist circumference measure
-intra-abdominal fat
Strengths of waist circumference
-closely linked to increased risk for chronic disease in both adults and children
-may provide a better indicator of chronic disease risk than BMI, especially in individuals with normal BMI values
Weaknesses of waist circumference
-does not directly measure intra-abdominal fat
-practitioner must be trained
-2-3 measures need to be taken and averaged
What do skinfolds measure
-body fat
What is the approximate error of skinfold measurements
-3.5%
What is the skinfold equation
-%body fat = (4.95 /density) - 4.50
Strengths of skinfolds
-relatively easy measurement with minimal equipment
-relationship between subcutaneous fat and total body fat varies with race, age and sex so population specific equations have been developed
Weaknesses of skinfolds
-calipers vary in quality, and some can be inaccurate
-intra and inter-rate reliability
-not recommended for people with BMI greater than 30 kg/m2
Factors that may contribute to skinfold measurement error
-poor anatomical landmark identification
-poor measurement technique
-inexperienced evaluator
-extremely obese or extremely lean participant
-improperly calibrated caliper
Bioelectrical impedance analysis
-estimates fat-free mass and total body water
-based on bodys ability to conduct mild electric current
Strengths of bioelectrical impedance analysis
-validated equation available for adults and children
-standard error estimates available for BIA published equation
Weaknesses of bioelectrical impedance analysis
-equations less valid for identify adiposity in individuals with high or low BMI values
-accuracy depends of following standardized procedures
BMI underweight value
-18.5
BMI normal weight value
-18.5-24.9
BMI overweight value
-25.0-29.9
BMI class 1 obesity value
-30-34.9
BMI class 2 obesity value
-35-39.9
BMI class 3 obesity value
-greater than 40
Landmark for measuring waist circumference
-measurement at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest
What does greater total body water mean in regard to BIA
-current passes more easily through the body
Which type of tissue has a lower water content than fat free mass
-fat tissue
In what individuals is BIA greater in
-individuals with more body fat
Siri equation to convert body density to body fat percentage
-%body fat = (4.95/density) - 4.50
What waist circumference is associated with increased risk of cardiometabolic disease in men
-greater than 102 cm
What waist circumference is associated with increased risk of cardiometabolic disease in women
-greater than 88 cm
