Body CompositionConcept and Utility

ByDr. Majid Abi Saab

Consultant RheumatologistAl Ahli Hospital

QA

Body Composition

Most methods consider body having two components:

• fat component, i.e. fat mass• fat-free component, i.e. fat-free mass (FFM)Body fat %• average values: women, ~25%; men ~15%• minimal values: women, 8-12%; men – 5%• considered obese: women, >30%; men >20%essential and non-essential fat

Reference body composition for man

Reference body composition for women

Ratings of % Fat (ages 20-29 yr)

Rating Men Women Excellent 6-9 10-17 Good 10-14 17-21 Acceptable 15-19 21-25 Too Fat 20-22 27-32 Obese >22 >32

Determining Ideal Body WeightIndirect approachesMetropolitan height–weight tablesbody mass index (BMI)• weight (kg) / height2 (m2)• ideal range is 18-25• >30 considered obese

Direct approaches• hydrostatic (underwater) weighing• anthropometric (skin-fold) measurements• bioelectrical impedance analysis (BIA)• air-displacement plethysmography (BOD POD volume)• DEXA The Most Accurate

X Y

x y

Bioelectrical Impedance

GE Lunar DEXA Body compositionFDA approved the LUNAR DEXA for Body Composition

Indications for use: The GE Lunar Body Composition“…management of diseases/conditions where the disease/condition itself, or it's treatment, can affect the relative amounts of patient fat and lean tissue. “Main indications: Obesity | Metabolic Syndrome | Chronic Steroids treatment | Back pain related android obesity.“Some of other diseases/conditions for which body composition values are useful include chronic renal failure, anorexia nervosa, AIDS/HIV and cystic fibrosis.

X-ray Source

X ray Absorption

Bone has a Higher X Ray Attenuation than Soft Tissue

DEXA PhysicsXray attenuation is depending on the amount, type of tissue and energy level

Bone

Soft Tissue

Low Energy High Energy keV

Abs(HE keV) = Abs(HE keV) ST + Abs(HE keV) BAbs(LE keV) = Abs(LE keV) sT + Abs(LE keV) B

Abs(HE keV) = Abs(HE keV) ST + Abs(HE keV) BI(HE keV) = Io exp(µHE.ST DST + µHE.B DB)

Abs(LE keV) = Abs(LE keV) ST + Abs(LE keV) BI(38keV) = Io exp(µLE.ST DST + µLE.B DB)

Abs

DST ; DB could be calculated and so MB =DB x AreaB

MST = DST x AreaST

Measure Bone/Fat/Lean Using DXA

-3Compartment model Define anatomical region Define bone area (green pixel) Calculate Bone mass using two energies Outside of bone region, R-value -> %Fat

using two energies Use local uniform composition over Bone

region to calculate total soft tissue and after fat - lean in each sub-regions

Calculate Total weight by summing up Fat, Lean and Bone masses for all sub-regions

Obesity Female (42years) (Height: 162 cm / Tissue (kg) (Fat +

Lean): 96,2 to 93kg)A/G decrease : DECREASE fat in android!

Fat (kg): 49,9 to 44,6 to 45,7 / Lean (kg): 46,2 to 47,4 to 47,3kg

Normal Weight Obese Syndrome Female (26 years) (Height: 158 cm / Total Mass (kg) : 54,8 to

52,3kg)Follow up case over 1,5 year

BMI from 22,2 to 21,2 (normal)

Normal Weight Obese SyndromeFemale (26 / H:158 cm / W:54,8 to 52,3kg) Tissue (kg) (FM + LM): 52,7kg to 50,2kg

What did she lose over 1,5 year, Fat and/or Lean?Fat (kg): 18,9 to 16,5 / Lean (kg): 33,7kg to 33,7kg

Ask yourself• Are you Obese?• Do you suffer from Obesity related disorders?

• Metabolic?• Chronic Back Pain, Knee/Hip OA?

• Do you have difficulties on making regular/sport activities?

• Is your HAQ within normal?

Weight Management

• diet modification• physical activity modification• behavior modification

Principles Common to Successful Programs

Weight Managementbased on Energy Expenditure (kcal/min) Activity 56 kg 83 kg

basketball 7.3 11.5

Circuit training 9.8 15.4

Cycling (9.4 mph) 5.6 8.3

Running (9 min/mile) 10.8 16.0

Running (7 min/mile) 13.3 18.5

Swimming (slow) 7.2 10.6

Swimming (fast) 8.7 12.9

Tennis (singles) 6.1 9.0

Walking (3.0 mph) 4.5 6.6

Sitting (quietly) 1.2 1.7

Weight Managementbased on Intake

Weight change = Calories (energy) intake – energy expenditure

Energy Intakecaloric density• CHO = 4 kcal/g• protein = 4 kcal/g• fat = 9 kcal/g• ethanol = 7 kcal/ginfluence of diet composition

Effects of low-energy intake on

RMR

Bray, Lancet, 1969

Your are offered a tiny part of Snicker’s candy bar.

It contains 6 g of fat and there is 100 kcal of energy.

What is the percentage of energy that comes from fat?

a. 6 kcalb. 600 kcalc. 6%d. 54%e. 60%f. cannot be determined

Weight ManagementCalculate % Intake from Fat Breakfast - McDonald's

Total Energy (kcal)

Fat (g)

Sausage McMuffin w/Egg 517 33

1% Milk - 8 oz 110 2

Hash Brown Potatoes 125 7

Lunch - Burger King

Bacon Double Cheeseburger 510 31

French Fries - regular 227 13

Chocolate Shake - 10 oz 374 11

Snack

Snicker's Candy Bar 280 13

Dinner - Taco Bell

Two Tacos 372 16

Combination Burrito 404 16

Pepsi - 24 oz 288 0

TOTAL (40% of intake from fat) 3,207 142

Weight ManagementBehavior Modification• avoid automatic eating• plan meals ahead of time• don’t serve self more food than should eat• avoid social binges• practice other stress management techniques• set realistic goals• incorporate physical activity into program

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