2.16 Body Composition and Energy Balance Flashcards
(22 cards)
What is body composition
A branch of human biology focusing on in vivo quantification of body components and how they interact.
What are some reasons for measuring body composition
- to assess nutrition quality and any specific nutritional problems
- to look for significant decreases in body composition which can indicate undernutrition - disease related undernutrition with inflammation, disease related undernutrition without inflammation or undernutrition without disease
- there are strong relationships such as between body composition and chronic disease and elevated fat mass and cardiometabolic disease
- there is a relationship between fat free mass and functional capacity, improving strength, balance and reducing mortality risks
What are the two different components of body composition
Fat mass and fat free mass
What is fat mass made up of
It is loose connective tissue mostly made up of adipocytes. It is either essential fat or storage fat
Essential fats are in tissues and organs (e.g bone marrow, nervous system and muscle), making up 3% of male mass and 12% of female mass.
Storage fats are energy reserves accumulating both cutaneously (beneath the skin) and viscerally (around organs). Storage fats form when eneregy intake exceeds energy expenditure (there is a positive energy balance)
Describe different fat mass distribution patterns
Android fat distribution is when fat accumulates around visceral organs and around the central abdomen. It is more common with men and can be associated with metabolic risk.
Gynoid fat distribution is the accumulation of fat around the hips and gluteal regions.It is higher in women for child bearing and it is not associated with metabolic risk
Where can fat mass cause damage
Fat mass around organs can cause damage, e.g liver and pancreas fat is associated with insulin resistance
What is fat free mass
Fat free mass is mass that does not have adipose tissue. It is made up of lean tissue, which is protein and body water, as well as bone.
What is fat free mass hydration
The proportion of fat free mass made of water, including intracellular and extracellular water (the extracellular to intracellular ratio stays fairly constant unless there is disease).
Describe changes in bone mass over time
Bone mass increases early in life and peaks early in adulthood, it then decreases from then onwards. Bone density is a determinant of bone strength, the minerals that determine density are primarily calcuim and phosphate
Describe changes in skeletal muscle mass over time
Skeletal muscle mass increases during adolescence, is stable from 30-40 and then decreases after, during old age rapid decrease can cause sarcopenia.
What factor can slightly modify organ size
Nutrition
What are the average changes in fat mass and fat free mass every year during adulthood
During adulthood the average person gains 0.5kg of FM and looses 0.2kg of FFM per year
Describe changes in bodyweight and BMI as you age
Body weight and BMI increase up until 70-80 when it declines due to hormonal and lifestyle factors
List some different body composition assessment methods
-BMI
-skinfolds
-hydrostatic weighing
-body volume measured by air displacement
-Bioelectrical Impedance Analysis
-DEXA
-MRI
-Digital Image Analysis
Describe BMI as a body composition assessment method
Is calculated as (kg/height (m) squared)
Is used as a screening tool to see if a person is underweight, healthy weight, overweight, class 1 obese, class 2 obese or class 3 obese (morbid) in clinical settings, field surveys and large scale population studies
Describe skin folds as a body composition assessment method
Where you pull skin and fat away from muscles and place skin callipers estimate thickness in mm of skinfolds at different body sites. It is based on the principle that subcutaneous fat is proportional to total fat. Equations are then used to give a body density estimate.
Describe hydrostatic weighing as a body composition assessment method
When body weight in the air is compared with body weight in water whilst holding breath, the residual volume of air in the lungs and GI are also taken into account. This is used to give estimates of density, FM and FFM. Someone with a higher FFM proportion will weigh more in water.
Describe body volume measurement by air displacement as a body composition measurement method
The amount of air displaced when subject sits in an enclosed BODPOD chamber. This can give volume and can then estimate density and body fat
Describe biological impedance analysis as a body composition measurement method
It measures impedance (opposition to a flow) by body tissues when exposed to a small alternating electric current. Then regression can provide FM and FFM estimates as non-aqueous mass gives a greater resistance than aqueous so current flows more freely through FFM.
Describe DEXA as a body composition measurement mechanism
An imaging technique with high energy and low energy beams where different masses reduce the signal at different extents
Describe MRI as a body composition measurement method
Strong magnetic fields and radio frequency signals interact with protons of the tissues to produce cross sectional areas and 3D images of tissues
Describe Digital Image Analysis as a body composition measurement method
3D optical body scanners are a recent tool to estimate body volume, circumferences and size at body parts
