Assessing Body Composition
Ana Carolina Paludo
Ana Carolina Paludo
Physiology of Sport and Exercise
carolina.paludo@fsps.muni.cz
Learning Objectives
▪ Concept of body composition
▪ Methods for assessing body composition
▪ Practical approach
Human Body Composition
Typical body composition of and adult man and woman
Body Composition: the body's relative amounts of fat
mass and fat-free mass (bone, water, muscle, connective
and organ tissue, teeth)
Essential fat: crucial for normal body functioning
Nonessential fat: adipose tissue
Body Composition Models
Two-Compartment model: divides the human body into fat and fat-free
mass.
Multi-component model: divide the human body into the atomic model, molecular
model, cellular model, and tissue system model.
Why assessing body composition?
Information about the % of body fat and fat distribution
The most important consideration is the proportion of total body weight that is fat
Estimating a healthy body weight and formulating nutritional recommendations/ exercise
prescriptions (over and underweight/fatness)
Estimating competitive body weight for athletes participating in sports that use body weight
classification
Monitoring the growth of children and adolescents and identifying those at risk ( under or
overweight/fatness)
Body changes associated with aging, malnutrition or obesity
Two Method Body Composition Assessment
Direct
• Chemical solution dissolves
• Physical dissection
Indirect
• Height, weight and BMI
• Hydro densitometry
• Air displacement plethysmograph
• Skin fold method
• Bioelectrical impedance analysis (BIA)
• Dual-energy X-ray absorptiometer (DEXA)
Height, weight and BMI
Body Height: measured by stadiometer
Body weight: measured by weighing scale
Body Mass Index (BMI): estimated by equation BMI= Weight (kg)/ Height (cm)2
BMI postive and negative factors
• A significant predictor of cardiovascular disease and type 2 diabetes.
• Is widely used in population-based and prospective studies
• Does not differentiate fat from lean body mass
• Athletes with a large amount of muscle mass can be wrongly classified
into the 'moderate or high-risk' categories
Hydro densitometry
Based on the density of the body
D= Mass/volume
Mass= measured by scale weight
Volume= 1. hydrostatic weighing (underwater weighing)
2. volume by air displacement
Archimedes' Principle: weight loss underwater is directly
proportional to the volume of water displaced by
the body volume.
Hydro densitometry - Calculation
Body density = Wa / (((Wa - Ww) / Dw) - (RV + 100cc))
Wa = body weight in the air (kg),
Ww = body weight in water (kg),
Dw = density of water (according to temperature)
RV = residual lung volume
100cc is the correction for air trapped in the gastrointestinal
tract.
Siri (1956): Fat % = [4.950 /Density - 4.500]×100
Brozek et al. (1963): Fat % = [4.570 /Density - 4.142]×100
Hydrostatic Weighing
• A most common technique used for decades
• The majority of indirect techniques have been validated
against hydrostatic weighing
• Time-consuming
• Difficult to perform on the aquaphobic
• Requires measurement of residual lung volume
• Impractical to measure a large number of people
Air displacement plethysmograph
• Measure the body volume and density using air displacement instead of
water to estimate the volume.
• Body volume is calculated by subtracting the air volume of the person
inside the chamber from the volume of the empty chamber.
• The individual sits inside the small chamber (Bod Pod)
• Computerized pressure sensors determine the amount of air displaced
by the person.
• After estimating the body volume is possible to predict the body density
and body fat.
• Take around 5-10 minutes.
Air displacement plethysmograph
Factors to consider:
• Individuals are tested wearing minimal clothing (a swimsuit)
and a swim cap to compress the hair.
• Individuals with excess body hair may affect the results
(underestimating).
Skinfold Thickness
• Based on the principle that the amount of fat beneath the skin is
proportional to total body fat
• Reliable measurement of the tissue gives a good indication of the percent
body fat.
• A simple anthropometric procedure that estimates body fat from the
close relationship between three factors:
1.Subcutaneous fat in adipose tissue deposits directly beneath the skin
2.Body's internal fat store
3.Body density of the intact human body
Skinfold Thickness Measurement
• Skinfold measurement is done with pressure
calipers
• Specific anatomical sites are measured, on the
right side of the body, three times (average or
repeated number is taken)
• The values are applied in predictive equations to
estimate body fat.
Skinfold Thickness Formulas
Bioelectrical Impedance Analysis (BIA)
• Based on the principle that the fat tissue is a less-efficient conductor of an
electrical current (1-10 uA).
• The easier the conductance, the leaner the individual
• Low-level electrical current is passed through the individual body and the
impedance or the opposition to the flow of the current is measured with a BIA
analyzer.
• It is possible to estimate body fat, lean body mass and body water
Bioelectrical Impedance Analysis (BIA)
• BIA devices are considered safe for most people
CAUTIONS:
• Anyone with an electronic medical implant
• Pregnant women
Factors that may affect the measurement
• Body weight: less accurate in obese people
• Hydration: dehydration may cause the fat-free mass (muscle and bone) to be underestimated
• Exercise: a recent exercise in high intensity may affect the accuracy
• Food and drink: recent food and drink intake may affect the accuracy. Overnight fasting is
more accurate
Dual-Energy X-Ray Absorptiometey
• A high-technology procedure that quantifies fat and muscle around bone areas of the body,
including regions without the bone present.
• Consists of a short exposure with low radiation dosage penetrates into the bone and soft
tissue areas to a depth of about 30cm. Specialized computer software reconstructs an image
of the underlying tissue.
• The computer generates a report that quantifies bone mineral content, total fat mass, and fatfree
mass.
Practical application - Sport
Maximizing Fat-Free Mass
Desirable for athletes involved in strength, power and
muscular endurance types of modalities in which the body
weight is moved through space.
Dehydration: impairs kidney and cardiovascular function;
impairing performance
Chronic fatigue: similar symptoms of overtraining
Severe weight loss
Practical application - Sport
Problems associate with very low levels of body fat
Too little body fat is associated with impairment in
reproductive health (low levels of testosterone and
estrogen); disorders in the immune system; lower bone
mineral density; increase risk of injuries.
In female athletes, increase the chance of the Female Triad
Syndrome: interrelationship of menstrual dysfunction, low
energy availability and decrease of bone mineral
Practical application - Sport
• Prioritize the body composition instead of weight
• Specific sport modality
• Sex and individual differences should be considered
• Methodological errors in body composition measurement should be considered
• A combination of diet and exercise is the best approach for optimal weight loss,
for athletes with no more than 0.5 -1.0kg per week until reaching the desired
body composition range.
To consider in sport settings:
carolina.paludo@fsps.muni.cz
Obrigada