Body Composition Made Simple
What is Body Composition?
Body composition is the percentage of body fat as per body weight. We all need fat for homeostasis and that is known as essential body fat. For men, it is usually between 3 to 5%. For females it is typically between 11 – 14%. However, determining the total fat mass and regional distribution is important to help identify any potential risk (especially in cases of obesity). In terms of distribution, the majority of total fat is stored on the body right below the skin and is known as subcutaneous fat. Visceral fat is fat stored in and around the organs.
The following is a table reference for percent fat classification for males (%):
· Essential – 3 - 5
· Lean – 6 – 10.9
· Fitness – 11 – 15.9
· Healthy – 16 – 19.9
· Moderate Risk – 20-24.9
· High Risk – greater than 25
The following is a table reference for percent fat classification for females (%):
· Essential – 11-14.9
· Lean – 15 – 18.9
· Fitness – 19 – 22.9
· Healthy – 23 – 26.9
· Moderate Risk – 27 - 31.9
· High Risk – greater than 32
Male pattern/abdominal fat storage (usually shaped as an apple) is android obesity, while female pattern/gluteal fat storage (usually shaped as a pear) is gynoid obesity. When referring to releases in fat cells, males typically have higher free fatty acid releases from the subcutaneous abdominal fat, while females have more resistance to fat mobility. This explains why beta-adrenergic cell receptors are usually found in males, which increase the release of free fatty acids from lower body storage, while alpha adrenergic cell receptors are usually found in females, and reduce the lipolytic response.
Tools to Identify Body Composition
There are different tools to help identify body composition. Height-Weight Tables (HWT) was first used to predict mortality rates for insurance premiums. However, the assumptions required are too many, that it is deficient; it fails to identify level of fat content. Lean mass affects the prediction, and there is no one single weight that is ideal for people with the same height. Body Mass Indicator (BMI) is the ratio of body weight to height squared, calculated by (lbs. + Inches^2) * meter and kg conversion factor of 703. Although, BMI has more practical uses and has its merits in the medical field, it still does not fully predict potential risks relation to body composition. The measurement of waist circumference can help assist BMI interpretations as large abdominal circumference is not due to muscle hypertrophy, allowing for the assessor to make the distinction between fat and muscle mass. Waist circumference further explains behavior-related fat storage.
Quick BMI references listed below
· Underweight = less than 18.5
· Normal = 18.5-24.9
· Overweight = 25.0-29.9
· Obese I = 30.0-34.9
· Obese II = 35.0-39.9
· Obese III = greater than 40.0
Another type of measurement is skinfold and is a fairly accurate prediction of fat mass. This type of test is directed for people that are not visibly obese, because some individuals have larger fat deposits in selected sites. Site locations (and fold direction) include: Abdomen (vertical), Chest (Diagonal), Thigh (vertical), Triceps (Vertical), Midaxillary (Vertical), Suprailiac (located by the “v-cut” region – Diagonal), Subscapular (Diagonal), and Medial Calf (Vertical).
Formulas related to skinfold are:
· 7-Site formula, which uses the sum of all of the above mentioned sites
· Body density = 1.112 – (.000043499*7-site) + (.00000055*7-site^2)-(.00029*age)
· 4-Site = sum of abdomen, suprailiac, triceps, and thigh
· 3-Site = sum of chest, abdomen, and thigh for males; sum of triceps, abdomen, suprailiac for females
· Percent Body Fat Males = (.3929 * sum of three skinfolds) – (.00105 * sum of three skinfold^2) + (.1577*age)-5.1885; sum of three skinfold in this case includes abdomen, suprailiac, triceps)
· Percent Body Fat Females = (.41563 * sum of three skinfolds) – (.00112 * sum of three skinfold^2) + (.3661*age) + 4.03653; sum of three skinfold in this case includes abdomen, suprailiac, triceps)
Other types of assessments are the following
· Waist-to-Hip Ratio – Circumference measure that predicts poor health consequences; different to waist circumference as there is no single universal standard. Calculated by dividing the waist by the hip, and the closer to 1, the greater the risk.
· Hydrostatic and Air Displacement – Density metrics that estimate body density ratio to body mass volume. Hydrostatic is similar to Archimedes principle of buoyancy (gold crown principle as we call it) where the weight lost under water is proportion to the volume of water displaced by body volume. Air displacement uses the same principles, but with air.
· Circumference Measurement – It estimates the body’s composition to calculate “girth measurement” in selected throughout different sites on the body. This helps information on the fat distribution patterns and body fat changes.
· Bioelectrical Impedance assesses fat based on water conduction. Fat contains less water than muscle, and the speed of conductivity can provide the information on the fat magnitude of the body. This type of test is one of the most accurate, but not really practical due to the equipment needed.
· Near Infrared Light– Test that emits light into the tissue and measures the light reflected back. Body fat absorbs light while muscle mass reflects it, ergo, the more light reflected, the less body fat.
Target Body Weight Formula
Body composition is directly correlated to health and fitness, meaning that we can monitor, test, and change based on our diet, rest, and activity. As mentioned before, higher the values of body of fat, assuming we have the essential fats, can lead to negative health outcomes. Therefore, we can predict body fat and determine a target of body fat that we should be in, and the tool we use is the target body weight formula.
It is calculated using a two-step process:
1. Fat Free Mass (FFM) = Body Weight – (Body Weight * Current Body Fat %)
2. Target Body Weight = FFM / (1 – Target Body Fat %)
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