How to Assess Body Weight and Body Composition

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How to Assess Body Weight and Body Composition

• Class 2
• Exercise, Diet, and Weight Management
• Instructor Samantha Rubin, MS, RD, CDE

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Overweight

• Refers to an excess amount of total body weight,
  including muscle, water and fat
• Can be overweight but not obese.
• May include individuals with a low body fat but
  high mass due to muscles.
• Body builders

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Obesity

• Refers to excessive body fat.
• Can be obese but not overweight.
• Normal body weight but still have excessive fat.
• Sedentary couch potato

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Height/Weight Tables

• Developed by insurance companies 1908 to
  determine insurance rates based on how long
  people were expected to live
• Lower weights were associated with lower
  mortality rates
• Identified an ideal weight range for height
• Not designed to predict disease risk
• Based on a non-representative sample of people
  between ages 25-59 who purchased life insurance
  (excludes people with major diseases)
• Many problems allowed for weight to increase
  with age, smokers and alcoholics lower body
  weight, not representative of the whole
  population (under-represents lower socioeconomic
  classes, minorities, and the elderly), weight and
  height were self reported, frame size not
  measured.

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IBW

• Ideal Body Weight, Hamwi method
• Women 5 feet, 100, add 5 pounds for every inch
  over 5, ex. 56 130
• Men 5 feet, 106, add 6 pounds for every inch
  over 5, ex. 57 148
• Subtract 2.5 for every inch below 5 feet.
• Small frame subtract 10
• Large frame add 10,
• Can give in a range of 5
• Can use to determine individuals IBW.
• Can adjust for obesity (ABW).
• Can subtract percentage for amputations.

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Example using IBW
Male, 510, large frame, current weight 200
lbs 106 lbs 60 lbs 160 lbs 160 lbs x 10 16
lbs 160 lbs 16 lbs 176 lbs Range 5 167 -
185 lbs To determine IBW Current weight / IBW
x 100 IBW 200 lbs / 176 lbs x 100 114 IBW
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Example using IBW and ABW
Female, 52, small frame, current weight 230
lbs 100 lbs 10 lbs 110 lbs 110 lbs x 10 11
lbs 110 lbs - 11 lbs 99 lbs Completely
unrealistic weight loss goal! Using ABW current
body wt - IBW x .25 IBW ABW 230 lbs - 99 lbs
131 lbs 131 lbs x .25 33 lbs 33 lbs 99 lbs
132 lbs Better, but.
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Try on your own!
Male, 57, large frame, current weight 280
lbs 1st step- calculate IBW 2nd step- calculate
the weight loss goal using IBW 3rd step-
calculate the individuals IBW 4th step-
realistic weight loss goal? 5th step- use ABW
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Step 1 IBW 57 106 lbs 42 lbs 148
lbs 148 lbs x 10 14.8 lbs 148 lbs 14.8 lbs
162.8 lbs 163 lbs Step 2 Weight loss goal
using range of 5 163 x .05 8 lbs 155 - 171
lbs Step 3 IBW 280 lbs / 163 lbs 1.72 x
100 172 Step 4 Realistic goal? 280 lbs to 163
lbs or even 171 lbs? Probably not! Step 5 ABW
280 lbs - 163 lbs 117 lbs x .25 29 lbs
171 lbs 200 lbs Better!
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Frame Size

• Wrist Method- use your index finger
• Elbow Breadth
• These are areas of the body less likely to be
  affected by weight gain.

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Limitations IBW/Hamwi
Disadvantages Determining frame
size Underestimates for short males and
females Advantages Easy Only height and weight
needed
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BMI

• Body Mass Index
• First published in 1836 by Quetelet
• Most common method currently in US and other
  countries.
• Helpful for assessing risk of health conditions.
• Provides guidelines for treatment plans.
• Weight kg / Ht m2
• Weight in kg pounds divide by 2.2
• Height in cm inches multiply by 2.54

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BMI Cutpoints Used in US
18.5 - 24.9 Healthy 25 - 29.9
Overweight 30 - 34.9 Obesity (class 1) 35 -
39.9 Obesity (class 2) gt 40
Severe obesity (class 3)
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Example of BMI calculation
Height 54 Weight 222 lbs 222 / 2.2 100.9
kg 64 x 2.54 162.6 cm / 100 1.63 m x 1.63
2.66 m2 100.9 kg / 2.66 m2 37.9 Obesity Class
2 Now try calculating your own BMI!
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Disadvantages of BMI

• Does not account for body composition or frame
  size
• Does not account for gender- males gt mass
• Can not use if amputations
• Different countries, different cut points

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BMI

• BMI over 25, goal is 10 weight loss
• Can use BMI to develop weight goal
• Ideal for cardiovascular disease is 22.6 for men
  and 21.2 for women
• HTN and diabetes if BMI gt 25 lose 3-5 kg
• Osteoporosis, 26-28 may be protection
• Over 65 years of age, lt 21 is defined as
  underweight.
• Average BMI of women age 30-49 is 26.7 in US.
• BMI correlates well with body fat percentage

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Cultural Differences

• Every one of these methods BMI, IBW,
  height/weight tables have been almost exclusively
  based on Caucasians.
• May make sense to add 10 with most of these, or
  use large frame for African Americans.
• For Asians, subtract 10 for IBW?
• Clinical judgement!

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Points to Ponder

• Men on average lie about their height by 1 inch
  or more,
• People shrink at least one inch, even 2-3 inches
  if they have knee, hip, or back surgery
• When weighing people, clothes can account for 3
  to 5 lbs (women 3 lbs, men 5 lbs)
• Preferable to weigh without shoes, same time of
  day, once a week, without clothes.
• 1 lb 470 ml or 16 ounces of fluid

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Body Composition Assessment
Adiposity- reflects an individuals degree of
fatness on a continuum of body composition. Body
fat standards related to mortality and morbidity
risks. As important as amount () body fat is
location of body fat. Central obesity larger
proportion of fat on upper half of the body,
abdominal, apple shape, android associated with
more chronic disease HTN, heart disease,
diabetes, gallbladder, high cholesterol
Peripheral obesity larger proportion of fat on
lower half of body (around hips), truncal,
glutealfemoral, pear shaped, gynoid more
difficult to lose
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Optimal Body Fat s
Different ranges for healthy body fat s Tend to
be lower when set by experts in sports medicine
versus health professionals working in weight
management. Optimal body fat ranges Men
10-20 Women 17-25 Obesity is when men have a
body fat gt 25 and women gt 32.
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Body Composition

• 50-70 of body is water
• 4 compartment model
• Body Cell Mass- skeletal muscle mass largest
  part- approximately 80 water
• Extracellular fluid- principal component of the
  vascular, lymphatic, and interstitial spaces- 95
  of the volume extracellular water
• Skeletal components- bones
• Adipose tissue- fat, brain, cell membranes
• The more body fat the less body water a person
  has
• Body composition assessment tools evaluate the
  above compartments.

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Waist to Hip Ratio

• Abdominal to Gluteal Circumference Ratio
• Measure waist girth and hip girth
• Measure standing, cloth tape measure
• waist mm narrowest or circumference of umbilicus
• hip mm largest circumference or max point betwn
  iliac crest and buttocks
• WHR gt 1.0 in males and gt .8 in females
  increased health risks, increased risk metabolic
  syndrome
• Person can have a normal body weight or BMI.
• Example
• waist 35, hips 45, female
• 35 / 45 .78
• at risk?
• Body fat distribution pattern?

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Waist Circumference

• Easier to use, and has been found to provide a
  better measure of abdominal fat than waist-to-hip
  ratio.
• Waist circumference greater than 40 inches for
  men and waist circumference greater then 35
  inches in women is associated with increased risk
  for chronic disease.

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SkinFold Thickness

• Commonly used
• Based on assumption that subcutaneous fat
  represents a certain proportion of the total body
  fat
• Specific sites are used on the body
• Should take two measurements or more at each site

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Skinfold

• Sites typically include chest, triceps,
  subscapular for men and triceps, abdomen,
  suprailiac for women
• Tables and equations are used to calculate the
  body fat percentage.
• Advantages easy, quick, inexpensive, takes into
  account age/gender
• Disadvantages dependent on technique, low
  reproducibility, doesnt give assessment of fat
  distribution, difficult in underweight and
  severely obese

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BIA

• Bioelectrical Impedance Analysis
• 4 electrodes- wrist and foot- painless- localized
  signal introduced and the impedance or resistance
  to flow is determined
• Tissues with large amounts of fluid conduct
  electricity better (fat free tissue and water)
• More body fat, greater resistance more muscle,
  less resistance
• With impedance value can determine body density
  and with body density can determine body fat

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BIA

• Advantages Easy to use, low expense, precise
  measurements.
• Disadvantages
• affected by hydration level, skin temperature,
  recent exercise, caffeine
• studied mainly on Caucasians

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Body Fat Assessment- Hydrodensitometry

• Based on principle that a body immersed in a
  fluid is acted on by a buoyancy force equal to
  the volume of fluid displaced.
• Individual expires maximally, submerged in water,
  underwater weight recorded
• air remaining in lungs must be corrected for-
  makes person buoyant
• Body fat is less dense than fat-free tissue
• More body fat, less dense, float more
• More muscle, more dense, sink more
• Lighter in water, more body fat
• Heavier in water, less body fat
• Using formula, determine body density and body
  fat.

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Disadvantages Hydrodensitometry
Gold standard but still disadvantages Margin of
error Difficult for individual Requires
experienced operator
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Bod Pod

• Measures by air displacement plethysmography
• Determines body volume from air displacement and
  percent body fat is calculated using equations.
• Easier to use than underweight weighing, no
  pinching, but expensive

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DEXA

• Dual Energy X-ray Absorptiometry
• Introduced 1981 originally bone density
• X-ray energy is transmitted through the body
  x-rays are absorbed differently by tissues of
  different densities.
• Very accurate can differentiate with precision
  low density fat and higher density fat free
  tissues
• Provides for three body components (fat free soft
  tissue, fat, bone-mineral)
• Can measure regional and total body fat content
  can determine distribution

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DEXA continued

• Advantages quick, painless, noninvasive,
  accurate.
• Disadvantages space and expensive piece of
  equipment some error
• DEXAs are replacing underwater weighing in many
  labs

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Additional Methods

• Measurement of a tracer in urine, blood, saliva
• CT images are being used to distinguish between
  visceral (intraabdominal) and subcutanous fat.

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Conclusion Assessment Overweight and Obesity

• For assessment body weight (overweight)
  height/weight tables, IBW/Hamwi, BMI
• For assessment body composition (obesity) fat
  skinfolds, circumference measures (WHR and waist
  circumference), BIA, DEXA, Bod Pod
• On any body fat assessment technique, the method
  is only as good as the technique and the measurer
• Most methods have a 3-4 margin of error or
  greater under the best circumstances.
• Clinical judgement!