fit ass lab 4
Fat mass/ body mass
% body fat equation
How to calculate % body fat?
1) Calculate the sum of the 7 (Average) skinfolds (SSF) measured for each type of caliper 2) Use the following equations to calculate body density (Db) - Jackson-Pollock Equation for Predicting %BF: - Male- Db = 1.112 - 0.00043499 (SSF) + 0.00000055 (SSF)2 - 0.00028826 (age) - Female- Db = 1.097 - 0.00046971 (SSF) + 0.00000056 (SSF)2 - 0.00012828 (age) 3) Use the following equation to calculate %BF for each type of calipers used. -Modified Siri Equation: %BF = [(495 / Db) - 450] * 100
Greater
Because fat is relatively low in water, individuals with a ________ % body fat will display a greater impedance
body weight (kg) / height (M^2)
Body Mass Index (BMI) equation
Densitometry
Db=body mass/body volume Hydrostatic weighing Bod-pod (air displacement)
Chest/Pectoral fold
Diagonal fold half distance between anterior axillary line and nipple (men) 1/3 distance (women)
Suprailiac fold
Diagonal fold in line with the natural angle of illiac crest
The Waist-to-Hip Ratio is a ratio of the circumference of the waist to that of the hips. Girth is the measurement of the middle of something, and traditionally refers to measuring around the waist. The relationship between girth and fat distribution can be gleaned from the WHR ratio. If the ratio is closer to one, then that means the fat is distributed in an unhealthy manner. If the ratio is close to .7 or .8, then that means the fat is distributed in a more healthy manner. Knowing someone's WHR is significant because knowing the location of the fat on the body is the most important factor for knowing the potential risk for that fat. If you are carrying excess fat around the waist and belly area, this abdominal/visceral fat makes you more likely to develop health problems and is linked to higher cardiovascular disease risk. This type of obesity is considered android (apple-shaped) obesity, and it is more common in males. Excess visceral fat is also linked to abnormalities, such as insulin resistance and an increase in LDL cholesterol levels, both of which are risk factors for heart disease. On the other hand, gynoid (pear-shaped) obesity is when the fat is distributed around the hips and thighs and is more common in females. This is a more healthy distribution of fat and is not linked to cardiovascular disease risk.
Explain how WHR gives information about the relationship between girth and fat distribution? Why is knowing someone's waist and/or hip girth significant? Which is better: android or gynoid obesity (explain the difference between these two in your answer).
The BIA estimates % BF through measuring electrical impedance and current flow through the body. It analyzes one's total body water (TBW). If someone has a high TBW, they will have a lower electrical impedance, and thus a lower % BF. If someone has a low TBW, they will have a higher electrical impedance, and thus a higher % BF. This makes sense because muscle and lean tissue has more water-content than that of fat tissue.
Explain how the BIA estimates %BF.
Direct body composition assessments directly measure the different components of the body by separating and weighing them. On the other hand, indirect body composition assessments, estimate body composition by obtaining indirect measures from the subject and plugging the values into formulas to obtain an estimate. The only direct assessment of body composition must be performed post-mortem. This is because direct measurement of body composition is done by dissecting the body and physically separating out the tissues into the desired body composition categories. Indirect assessment of body composition can be obtained using densitometry. Densitometry is used to find the density of the body which can then be plugged into formulas such as the Siri Equation. Two types of densitometry assessments that can be performed are bod pod and hydrostatic weighing. Both assessments predicate upon Archimedes Principle and measuring the amount of water (hydrostatic weighing) and air (bod pod) is displaced by the subject. DEXA or Dual-Energy X-ray Absorptiometry can also be used to indirectly measure body composition by passing x-rays through the subject and estimating bone mineral mass, fat mass and lean tissue mass based on each component's unique absorption spectrum. Field tests to indirectly estimate body composition include, skinfold assessment, bioelectrical impedance analysis and anthropometry (like waist-to-hip ratio). DEXA is an indirect assessment of body fat percentage because it does not physically separate the components and measure them. Instead, x-rays are passed through the body and estimates of the differences in body tissue (fat, muscle, and bone) are made.
Explain the difference between direct and indirect assessment for body composition (%BF). Is DEXA a direct or an indirect assessment of %BF?
BMI is generally not a good measurement because it fails to consider body composition. BMI is inaccurate for obtaining a general health indicator for both obese individuals and severly muscular individuals. The BMI measurements of these two people may be very similar, even though the distribution of fat and muscle is extremely different for the two people. For example, a man who has 8% body fat is 6'0 ft (1.83m) and weighs 205 lbs (92.98kg) would have a BMI of 27.8 which is considered overweight by the BMI scale. This person is not overweight but just carries more muscle than the average individual, so his BMI does not estimate his health accurately. On the other hand, someone who is carrying little muscle mass but significantly more fat could be considered normal by the BMI scale. For example, a man who has 25% body fat is 6'0 ft (1.83m) and weighs 180 lbs (81.65kg) would have a BMI of 24.4, which is considered normal by the BMI scale. Clearly, the man in the first scenario is a healthier individual, but according to the BMI scale the man in the second scenario is considered normal and healthier.
Explain why BMI would be inaccurate in some populations?
Body mass - fat free mass
Fat mass equation
Low impedance (good current flow)
High total body water
The BIA analyzer assessing % BF is probably not that accurate compared to a skilled technician using a metal caliper to assess % BF during a skinfold assessment. There are many possible sources of error for this method of body composition assessment. First, since it measures electrical impedance through measuring total body water (TBW), one can receive a body fat percentage that is not accurate if they are hyper- or hypohydrated. For example, someone who is very hydrated will have a higher TBW, a lower electrical impedance, and thus a % BF that is probably underestimated. Also, calibration differences among device types and brands of BIA will provide slightly difference % BF readings.
How accurate do you think the BIA analyzer assessed %BF? What are some possible sources of error for this method of body composition assessment?
1/3
How much of the total body fat is assumes to be subcutaneous
Waist to Hip Ration (WHR)
Indirect measure of upper and lower body fat distribution Estimate of central adiposity
High impedance (poor current flow)
Low total body water
Bioelectrical Impedance Analysis (BIA)
Measures resistance to flow od electrical current
> 40
Morbidly Obese BMI
One advantage of using the DEXA for body composition assessment is this machine accounts for individual variability in bone mineral content, which makes this method more reliable and accurate than the other body composition assessments. Another advantage of using this machine is this test is fast and comfortable for the subject, which is an advantage for patients who have low subject compliance. It is also easy to administer for the technician, although they need to be trained. One disadvantage for using DEXA for body composition assessment is this machine requires a trained technician to operate the DEXA, which requires money to pay for the trained technician. The DEXA machine itself is also very expensive. Another disadvantage of using this machine is x-rays are being transmitted through the body. Although low doses of radiation are being transmitted, this still increases radiation exposure in the subject.
Name two advantages and two disadvantages to using the DEXA for body composition assessment.
Pre-test instructions for BIA
No eating/drinking 4 hours before No mod-vigorous exercise within 12 hours Void bladder within 30 min No alcohol consumption 48 hours prior No diuretics (coffee) before test Do not test female clients if "they feel they are retaining water" aka on period
18.5 - 24.9
Normal weight BMI
>30
Obese BMI
25-29.9
Overweight BMI
Percent body fat
Population-specific equations are used to convert Db--> ________
Duel-Energy X-ray Absorptiometry (DEXA)
Reference method for assessing body composition Low level x-rays bone density
Benefits of BIA
Similar predictive accuracy of skinfold less invasive can be used on obese clients inexpensive little technical skill involved faster
Skinfold is a good measure of subcutaneous fat (there has been evidence of a good correlation between 12 site skinfolds and MRI)
Skinfold assumption #1
The distribution of fat (sub-q vs internal) is similar for all individuals within each sex
Skinfold assumption #2
There is a linear relationship between the sum of skinfolds and Db
Skinfold assumption #3
indirectly
Skinfolds ______ measure subcutaneous thickness of adipose tissue at various sites on the body
Sum
The _______ of the individual skinfold measures is used in a prediction equation to determine Db
< 18.5
Underweight BMI
Thigh fold
Vertical fold midway between proximal border of the patella and inguinal crease (flex knee to find)
Tricep measure
Vertical fold Posterior aspect of the upper awm Halfway between the acromion and olecranon processes Mark with arm bent but measure with arm hanging freely at side
water, protein, minerals, fat
What 4 thing is the body composed of?
metal, plastic, electronic
What are the 3 types of calipers?
Skinfold, BMI, WHR, BIA
What are the 4 methods for determine body composition?
The most obvious source of error from using this skinfold method would be inexperience of the test administrator. Since this was our first experience with skinfold calipers, error in recording the thickness of the skinfolds is bound to happen. Another source of error could originate from the participant having exercised soon before the skinfold testing or from the participant's lotion which makes it difficult to grasp the fold. Given that the type of caliper is a potential source of error during measurement, there are three things we can do to stay consistent and minimize more error. First, we should place the caliper halfway between the trough and the crest of the fold. Second, we should measure the same side of the body during the assessment, preferably the right side, to stay consistent. Lastly, the test administrator must make sure the measurement lengths and sites are accurate and checked twice before going in to pinch for the fold.
What are the potential sources of measurement error when using the skinfold method? Given that the type of caliper is a potential source of measurement error, identify three suggestions to minimize such error.
Total body water
What does BIA directly measure?
CVD risk and mortality
What does the WHR correlate to?
A skinfold test would not be ideal for an obese population because the calipers may not be able to fit around the fat of an obese person. If the skinfold test was still conducted, it may severely underestimate the percent body fat. This could also make the person feel ashamed and humiliated, which would lead to a poor professional relationship.
What population might skinfold testing NOT be ideal for and why?
Right
What side of the body do you measure for skinfolds?
When 2 values differ by more than 2mm
When do you perform a 3rd skinfold measurement at the same location?
When using the Omron BIA scale in class, you should start by: - Pressing the power button. Allow a few seconds for the system to calibrate. - Once calibration is complete, press guest and insert your age, gender, and height (pressing set in between completing each option). - Next, the subject can step on the scale. Make sure the subject is barefoot. They should hold the handle bar and extend their arms out in front of them horizontally. - The weight of the subject should be displayed first. After a few more seconds, the weight number will disappear and the system will continue to calculate the %BF through the electrical impedance. - The %BF number will display and you should record your results
Write out the step-by-step instructions for using the Omron BIA scale used in class. Start your instructions with turning the machine on.
Subscapular fold
diagonal fold ~45 degree angle 1-2 cm below the inferior angle of the scapula
Andriod
refers to stomach
Gynoid
refers to thigh
Abdominal fold
vertical fold 2 cm to right of belly button
Midaxillary fold
vertical fold on the midaxillary line at the level of the xiphoid process of the sternum braline