Body Composition Flashcards
Why is measuring body composition important?
Health status indicator, optimal performance, monitor changes (growth, aging, disease), evaluate treatment efficacy. Excess fat is associated with many diseases.
Define Fat Mass (FM) and Fat-Free Mass (FFM).
- FM: all extractable lipids.
- FFM: lipid-free chemicals and tissues
Define Essential Lipids and Lean Body Mass (LBM).
Essential Lipids: compound lipids (phospholipids) for cell membrane formation. LBM: FFM + essential lipids.
Define Relative Body Fat (%BF)
FM expressed as a % of total body weight
How does essential fat differ between males and females?
Females = 12%, Males = 3%. Too little fat can be detrimental to health because essential fat is important for organ function
What aspects of body composition are important to consider when measuring?
Total amount/proportion, location, and “quality”.
What is visceral fat and how can it be measured?
Visceral fat can be measured with CT scan or MRI and is associated with risk of diabetes
List the body composition techniques discussed.
Bioelectrical Impedance Analysis (BIA), Duel X-ray Absorptiometry (DXA), Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Body Mass Index (BMI), Waist Circumference (WC), Waist-to-Hip Ratio (WHR)
How does Bioelectrical Impedance Analysis (BIA) work?
Chemical approach. Tissues have different impedance (resistance) to electrical current. More water = less resistance. Fat = less water, Muscle & “other” = more water
What outputs does BIA provide?
% body fat, some measure Total Body Water (TBW)
What are the benefits of using BIA?
Inexpensive, safe, portable, easy to use, 2 or 3 compartment model.
What are the weaknesses of BIA?
Low accuracy/validity, typically underestimates BF%. Many things can interfere with a “good signal” like hydration status, temperature, limbs touching
How does Duel X-ray Absorptiometry (DXA) work?
Two sources of low dose X-ray radiation pass through the body
What outputs does DXA provide?
FM + FFM + BM, total and regional FM content
What are the benefits of using DXA?
“Gold standard” for bone mineral content, non-invasive, quick, regional body composition, highly reliable/valid, 3 compartment model
What are the weaknesses of DXA?
Expensive, large equipment, not portable, requires trained technician, cannot measure intra-abdominal fat (some formulas exist to estimate it).
How does Computed Tomography (CT) work?
Anatomical approach. Rotating X-ray
What output does CT provide?
3D image of internal structures
What are the benefits of using CT?
Highly reliable/valid, important for disease management (e.g., cancer), 4 compartment model. It can separate fat (visceral vs subcutaneous), bone, muscle mass, and othe
What are the weaknesses of using CT?
Expensive, large, requires a trained technician, high dose radiation exposure.
How does Magnetic Resonance Imaging (MRI) work?
MRI uses magnets and radio waves to produce images on a computer. MRI does not use ionizing radiation
Anatomical approach. Big rotating magnet.
What output does MRI provide?
3D image of internal structures
What are the benefits of using MRI?
No radiation, highly reliable/ valid, important for disease management (e.g., cancer), 4 compartment model. It can separate fat (visceral vs subcutaneous), bone, muscle mass, and other
What are the weaknesses of using MRI?
Expensive, large, requires a trained technician, claustrophobia
Why isn’t liposuction effective for metabolic complications?
Losing weight in visceral fat leads to decreased metabolic complications
How does Body Mass Index (BMI) work?
BMI is a calculated measure of a person’s body weight (in kilograms) divided by the square of their height (in meters)
Anatomical approach. Weight to height ratio
What output does BMI provide?
Index of relative weight. Units: kg/m2
What are the benefits of using BMI?
Fast, easy to measure, low cost, minimal participant involvement. Correlated to many health outcomes (epidemiology studies). Screening/tracking tool
What are the weaknesses of BMI?
Not appropriate for some populations. Tells you nothing about location or quality of weight
How does Waist Circumference (WC) measurement work?
Anatomical approach. Measure of the circumference of the waist
What output does WC provide?
Waist circumference. Units: cm
What are the benefits of using WC?
Fast, easy to measure, low cost, minimal participant involvement. Screening/tracking tool. Abdominal region specificity
What are the weaknesses of using WC?
Individual vs population level indicators
How does Waist-to-Hip Ratio (WHR) work?
Anatomical approach. Waist to hip ratio
What output does WHR provide?
Ratio. No units
What are the benefits of using WHR?
Fast, easy to measure, low cost, minimal participant involvement. Screening/tracking tool
What are the weaknesses of using WHR?
Two people with very different health risks can have the same WHR
How do BMI, WC, and WHR relate to heart attack (MI) risk?
As WHR increases, risk of MI increases. As WC increases, risk of MI increases. As hip increases, risk of MI decreases. BMI increase elevates OR of MI
What are intramuscular lipids/fat?
Fat located within the skeletal muscle fibers. Associated with T2D risk. Energy store during exercise
What is the relationship between intramuscular lipids and insulin resistance?
Increase in intramuscular lipids decreases insulin stimulated glucose disposal (i.e., increased insulin resistance)
How do lipid size and mitochondria relate to insulin sensitivity?
As lipid droplet size decreased, insulin sensitivity increased. As mitochondria size increased, insulin sensitivity increased
What is white adipose tissue (WAT) and what are its functions?
Energy storage, insulation, protection/packaging, endocrine role, inflammation
What is brown adipose tissue (BAT) and what are its characteristics?
Production of body heat without shivering. Brown color due to presence of more capillaries and mitochondria. Numerous/smaller lipid droplets vs. white adipocytes
What is beige adipose tissue and how does it relate to white and brown fat?
White adipose tissue contains darker adipocytes that come from same precursors as WAT. Beige has mitochondria so it can produce heat. Beige contains iron that gives it its distinct color
What are hyperplasia and hypertrophy in the context of adipocytes?
Hyperplasia = growth of new cells. Hypertrophy = increase in volume.
How do adipocytes change in lean vs. obese individuals?
Increase in body fat mass from lean to obese occurs primarily through an increase in the size of the cells (hypertrophy), however the conversion between obesity and severely obese occurs through an increase in cell number (hyperplasia)
What happens to adipocytes during weight loss?
Weight loss results in the decrease of the volume of adipocytes but doesn’t change the number
What are apoptosis and necrosis?
- Apoptosis: controlled and mostly non-inflammatory cell death.
- Necrosis: cell death involving macrophage recruitment and inflammatory responses.
How does cell death occur in white adipose tissue?
Cell death of fat cells in white adipose tissue occurs primarily by necrosis-like cell death and involves an inflammatory response
What are the differences between subcutaneous and visceral obesity?
More macrophages in individuals with visceral obesity leading to more inflammation - insulin resistance, T2D etc
What should be considered when assessing body composition?
Consider absolute amount, relative amount, location, and “quality.” Body composition is but one factor to estimate “risk” or “performance”
