Body composition & obesity Flashcards
What is body composition?
“The study of human body composition can be defined as a branch of human biology which mainly focuses on the in vivo quantification of body components, the quantitative relationships between components and component alterations related to various influencing factors”
What are the five body composition levels?
I. Atomic, II. Molecular III. Cellular IV. Tissue-system V. whole body.
What is the biggest measurement in:
I. Atomic, II. Molecular III. Cellular IV. Tissue-system V. whole body.
Atomic: BW = O(!) + C + H + N+ Ca + P + S + K + Na + CL + Mg
Molecular: BW = lipids, WATER, protein, bone mineral, soft tissue mineral, glycogen
Cellular: BW = CELL MASS, extracellular fluid, extracellular solids
Tissue/systems: BW = adipose tissue, SKELETAL MUSCLE, skeleton, viscera, blood, others
Whole body: BW = head, neck, trunk, lower extremities, upper extremities.
What are the different BC-methods depending on BC-levels?
I: neutronactivation IVNAAA,
II: IVNAA + water dilution,
III: TBK +DXA + Bromide dilution,
IV CT/MRI/DXA + blood dilution,
V: general status.
How is different BC divided?
2- compartment model is dived into FAT and FFM (fat free mass) uses BIA, TBK, TBN, TBW
3- compartment model is dived into fat, lean tissue and BMC uses DEXA
4 comportment model is dived into fat, ECW, BCM, FFECS
Multicompartment chemical model is dived into fat, water, glycogen, TBP and mineral measurement often to complicated to be practical
What measurement is done on a 2-compartment model?
Anthropometry, Densitometry, Dilusion methods
Describe anthropometry.
Anthropometry: Upper-arm anthropometry (arm circumference and TSF. If you know the circumference and the thickness of the dat -> calculations can be done.
Describe densitometry.
Densitometry: UWW(underwater weighing, not very useful for clinical use more for physiological research, by knowing the density of dat and FFM the % fat can be calculated) and plethysmography(Ppl is but into a box that is sealed., depending on the pressure change the volume can be calculated, together with weight it is possible to calculate %fat. Expensive machine but useful)
Describe dilution methods.
Dilution methods: total body water(?, uses deuterium dilution D2O, tritium dilution T2O, labled oxygen dilution O18 and bioelectric impedance BIA) and total body potassium (measurement of naturally occurring 40K (0.012% of K) in a shielded whole body counter. Estimates body cell mass via intrecellular [K], VCM (kg) = 0.0833 x TBK(mmol),not so difficult for the patient but the equipment is expensive)
Describe bioelectric impedance
Bioelectric impedance(indirect method, measures resistance and reactance. The resistance increase with a higher fat content, compare to standard curve.
Model assumptions include fice-cylinder body model(far from perfect), “shape factor” in BIS calculations, resistively constants – constant or variable?, body height as proxy for distance between electrodes.
Includes different method: single frequency BIA: FFM and TBW – difficult separating ICW and ECW, unsuitable in altered hydration states., Multi-frequency BIA: FFM, TBW, ICW and ECW from regression equations, bioelectrical spectroscopy (BIS): FFM, TBW, ICW and ECW from mathematical modelling of multiple frequencies Electrical properties of tissue are frequency-depemdemt, the ,easurment range is between 1MHz and 5kHz, Bioimpedance spectroscopy (BIS) can measure the physiological impedance curve, the measurement principle is using high frequence so the curret flows through the cells.
What is the difference of using BIS vs DXA for measuring FFM (fat free mass)
– ok for healthy, but not in diseases?
Conclusions: BIA values are affected by numerous variables, including: body positions, hydration status, consumption of food and beverages, ambient air and skin temperature, recent physical activity, conductance of ecamining table, BIA is convenient, portable and works well in health subjects and in patients without disturbed water/electrolyte equations, BIA is NOT valid in extreme BMI <16 >34 or major hydration shifts (ascites, inflammation), impedance spectroscopy & segmental BIA could possibly be proven useful in those cases.)
What is DXA and what can it measure?
DXA – dual energy X-ray absorptiometry: measures bone mineral (BMC), fat (BF), fatfree soft lean tissue (LSTM), skeletal-muscle mass (TBSM), andro/gyno fat localisation ratio (central/distal), C% = 1-3%
How can you measure muscle mass?
CT/MRI, DXA, bioimpedance, anthopometry, many functional tests in use.
Name some obesity related complications?
CVD: hypertension, ischemic heart disease, heart failure, stroke
Metabolic: diabetes, impaired glucose tolerance, elevated triglycerides, low levels of HDL, elevated uric acid & gout.
Respiratory: Sleep apnea, pickwick syndrome
Gastrointestinal: Biliary stones 6-23% M-F, liver steatosis >90%, liver steatohepatitis 50%, pancreatitis 1-2%.
Mechanical: artitis, depressed physical performance, increased surgical risks.
Urogenital: prostatic hyperplasia, urinary incontinence, menstrual dysfunctions, infertility, kidney stones
Miscellaneous: cancer, mental dysfunction.
What are some treatments for obesity?
Decrease energy intake: total starvation, intermittent fasting (5:2), VLCD (12-20 w before op, obtain better results), low energy diets (LCHF), behaviour modifications, anorectic drugs, surgery(gastroplastly, gastric by pass)
Increase energy expenditure: physical activity, thermogenic drugs – ephedrine, thyroxine
Increase fecal energy losses: malabsorptive drugs (orlistat, akarbos), ileal by pass
The macronutrient is not the way to fight obesity?
Normal built human - 10 weeks of starvation is possible (human is allowed to drink water)
For 70year old man - 20 weeks of starvation is possible
When clinically the person of course gets micronutrient
The problem is to keep the weight off
