Module 1: Obesity - Development, diagnosis, and measurement

Obesity is a

global disease burden

obesity rates have ________ since 1975

tripled

_____ of adults are overweight

39%

_______ of adults are obese

13%

dramatic increases worldwide in

high and low income countries

rise of obesity is too rapid to be explained by

genetics alone, environemental and behavioral changes play a role

definition of obesity from Obesity Canada

a progressive chronic disease characterized by abnormal or excessive fat accumulation that may impair health

obesity is a leading cause of

• type 2 diabetes

• high blood pressure

• heart disease

• stroke

• arthritis

• cancer

  • etc.

obesity is one of the

leading causes of preventable death - smoking is another one

body mass index

universal definition of overweight and obesity

BMI =

weight (kg)/height (m)²

underweight BMI

<18.5

normal weight BMI

18.5-24.9

overweight BMI

25.0-29.9

obese class I BMI

30-34.9

obese class II BMI

35.0-39.9

obese class III BMI

> or equal to 40.0

there are many cautions in using ______ alone to determine obesity

BMI - because everyone stores body fat differently

Waist circumference (WC)

used alongside BMI to assess risk of Obesity-related complications

WC is associated with

chronic disease

2 ppl can have the same BMI, but one might have a larger WC

this is a strong indicator of obesity associated with health consequences

WC cut-off point for risk of developing health problems - men

> or equal to 102 cm or 40 in

WC cut-off point for risk of developing health problems women

>or equal to 88 cm or 35 in

unit for BMI

kg/m²

having a higher BMI and higher WC is a strong indicator of

increased reisk of type 2 diabetes, hypertension, and CVD

NHLBI guidelines not that increased WC can indicate increased disease risk

even in individuals considered normal weight

BMI only takes body size into account, and not

body composition

BMI has

no information on fat distribution

BMI is hard to

interpret across ethnic groups or those losing muscle mass (elderly people)

some ethnic groups have

greater risk of disease at given BMIs than other groups

As an older person,

Losing weight very fast is a concern as it could be due to sarcopenia (losing muscle mass), regardless of BMI

BMI can be normal, but

weightloss can be seen as unhealthy (sarcopenia)

ethnic disparities are major in health

it comes down to genetics

more than two times as likely to develop diabetes at a given age

Asians (followed by Hispanics, and then Black people)

have a higher body fat for a given BMI

Asians

at the same BMI, 5% more body fat in _______ than Dutch people

Indonesians

BMI caps should be different for different ethnicities because

cut offs should be lower for ethnicities that have a higher body fat at given BMIs. which is often missed when blanket BMIs are used

Why is BMI often used when it is imperfect and imprecise

it is simple, makes it the best

BMI is imperfect and impercise because

it does not measure fat tissues, which defines obesity

body composition

the body’s relative amounts of fat and lean body tissue(FFM)

FFM

fat-free mass

components of FFM or lean body tissue

• muscle

• bone

• water

• organ tissues

components of fat mass

• essential fat

• stoarge fat

essential fat is

required for normal physiological function. having too little is a risk factor

essential fat consists of

• major organs

• muscles

• central nervous system

essential fat accounts for ______ total body weight in males

3-5%

essential fat accounts for _____ total body weight in females

8-12%

less than _____ essential fat making up total body weight in females is concerning

12%

males have a higher percentage of _____ in their body composition

muscle

males have a lower percentage of _____ in their body composition

essential fat

females have a higher percentage of _______in their body compostion

essential fat

females have a lower percentage of _______ in their body composition

muscle

females have more ________ than males

essential and storage fat

dual energy X-ray absorptiometry (DEXA)

• gold standard direct method of measuring body composition

• uses series of low-dose, transverse radiation scans, providing high degree of accuracy

• provides measurements of bone mineral (density), and non bone lean tissue (able to measure visceral fat as well - fat mass, bone mass, nonbone mass - muscle, organs, water

• con: very expensive

magnetic resonance imaging (MRI)

• direct method (gold standard) of measuring body composition

• better quanitification, more precise than DEXA

• muscle mass

• visceral fat

hydrostatic (underwater) weighing

• indirect, lab-based method of measuring body composition

• go into a pool of water

• histortically most commonly used. lab technique for measuring % body fat

• uses whole body density to calculate body composition based on Archimedes’ principle

• cons: time-consuming, not feasible to test large numbers of athletes

• how much water you displace based off info on body densities - can calculate what proportion of body fat and muscle after you displcae water

how does hydrosatic weighing work

• measures underwater weight - exhale all air an submerge while on scale

• bone and muscle are denser than water (sink), fat tissue is less dense (floats)

• higher underwater weight means more lean mass, lower underwater weight means more body fat

higher underwater weight means

more lean mass, because bone and muscle are denser than water (sink)

lower underwater weight means

more body fat. because body fat is less dense than water and floats

bodpod

• measures body composition through air displacement - fat mass, percent fat, lean mass

• indirect, lab-based method of measuring body comp

• calculates % BF from body density (similar to hydrostatic weighing)

• uses computerized air pressure sensors to determine amount of air displaced

field/clinic methods of measuring composition

give ideas of fat mass and location of fat mass

skin folds

natural areas of body where skin overlaps and rubs against itself (field/clinical method)

waist-to-hip ratio

method of field/clicial method to see measuring of body composition

Archimedes’ principle

fat is more buoyant than lean tissue

Biometrical Impedance Analysis (BIA)

• rapid, noninvasive and inexpensive method of measuring body comp

• sends electrical current through the body to estimate body fat (based on principle that fat is less conductive than lean tissue) - conductants of current

• cons: possess a higher degree of measurement error (measurements may be affected by subject’s hydration status) - hard to control worldwide, become a global measure

fat is less conductive than

lean tissue

men risky - high body fat

over 30%

men excess fat

21-30%

men moderately lean

13-20%

men lean

9-12%

men ultra lean

5-8%

men risky (low body fat)

under 5%

women risky - high body fat

over 40%

women excess fat

31-40%

women moderately lean

23-30%

women lean

19-22%

women - ultra lean

15-18%

women risky - low body fat

under 15%

waist to hip ratio =

waist/hips

male excellet waist to hip ratio

under 0.85

male good waist to hip ratio

0.85-0.89

male average waist to hip ratio

0.90-0.95

male at risk waist to hip ratio

over 0.95

female excellent waist to hip ratio

under 0.75

female good waist to hip ratio

0.75-0.79

female average waist to hip ratio

0.80-0.86

female at risk waist to hip ratio

over 0.86

BMI pros

• costless (requires no equipment)

• noninvasive

• easy for assessing large populations

BMI cons

does not account for % fat and FFM - not useful for athletic populations

Waist-to hip/ body girth pros

• low cost

• easy to measure/calculate

waist to hip/body girth cons

prediction equation possesses high degree of error

skinfolds pros

• low cost

• easy to use

• time efficient

skinfolds cons

• slightly invasive

• requires certain degree of skill to measure accurately

hydrostatic weighing pros

high degree of accuracy

hydrostatic weighing cons

• time consuming

• requires pool/water tank

• requires certain degree of skill to use

air displacement (bodpod) pros

• easy to use

• time efficient

• high degree of accuracy

air displacement (bodpod) cons

very expensive

bioelectrical Impedance Analysis (BIA) pros

• fairly low cost

• easy to use (can be self-administered)

• time efficient

biolectrical impedance analysis (BIA) cons

sensitive to subject’s hydration status - has high degree of error

DEXA pros

• very high accuracy

• noninvasive

• includes measure of bone density