Lecture 4 - Body Composition Flashcards
What is body composition
Proportion of muscle, fat and bone mass in body.
Important for health and performance, body composition is what helps us survive.
Risks of being under/overweight
overweight:
stroke, cancers and diseases
underweight:
malnourished, osteoporosis
Three different models of body comp
2-c: fat and fat free mas
3-c: lean mass, fat and bone
4-c: fat, protein, water, bone
Function of fat and two types
fat helps as insulation, provides protect and used as energy storage
Essential fat is found its tissues, marrow and organs used for physiology function (women more then men due to child birth)
Storage fat is stored in adipose tissue and is just beneath skin. There are two types of adipose tissue
Two types of adipose tissue
Visceral: found around major organs, visceral is the more dangerous fat
Subcutaneous fat is found beneath skin
Two types of obesity
Android: trunk and abdominal, more commonly seen in me
Gynoid is hips and thighs, more commonly seen in women
Stable isotope dilution technique
Test that measures free fat mass as water stored in everywhere but body fat. Baseline concentration of tracer is measured from body fluid. Fat free mass is then calculated by dividing TBW and hydration factor
Pros: Accurate measure of total body water
Cons: Costly, time consuming and need a lab
Underwater weighing (hydrodensitometry)
Calculating total density body by immersing a human in a fluid that is equal to the weight of a human. weight of water is displaced by volume of body to be calculated for for BF%
Pros: Accurate FFM measurement
Conss: costly, lab, high patient burden
Air displacement plethysmography
Air displacement plethysmography relies on similar principles to the underwater weighing to estimate total body volume. Pod measures pressure within the pod with and
without participant in it
Pros: Accurate with less patient burden
Cons: Costly and requires lab
Bioelectrical impedance
Bioelectrical impedance provides body composition by measuring the impact of adiposity on opposing electrical current flow. Uses Ohms law V=IR (v= voltage, I= electrical current and R= resistance). Overall impedance is calculated by sending a small electrical current through the body and measuring the voltage difference
Pros: Convient, Portable and cheap
Cons: Different types of devices with varying accuracy
Skin fold measures
Measuring skinfold thickness at various sites across the body. The adding it up to calculate BF% using equations
Pros: Portable simple and inexpensive
Cons: accuracy dependant on measurments that require training to take
Dual-energy X-ray absorptiometry (DXA)
DXA relies on emitting high and low energy X- ray beams through the body. Utilizes 3-compartment model: Fat mass, Lean mass, Bone mineral content. Laying on face
Pros: Accurate determination of results. low radiation and burden on patient
Cons: costly and requires lab
What is BMI?
BMI=weight (kg)/ height (m^2)
Used many years for proxy of adiposity and helps inferences on disease risk but does not differentiate fat mass from fat free mass
