Unit 9 - Obesity to Underweight: The Highs and Lows of Weight Status

phed 2007

Body Composition: Obesity to UnderweightHealthy Body Weight

Science defines a healthy body weight based on _____________________ from all causes.

1. Weight for height

2. Fat _________________

3. Absence of __________ ______________ associated with obesity

(e.g. cholesterol, blood glucose, BP)

Measuring Body Composition

Body Mass Index (BMI) Defines average relative weight for height in people older than 20 years

Often correlates with degree of body fatness and disease risk

Calculated by _____________ your weight (kg) by your height (m2)

Does not distinguish between __________ and ___________________ tissue

Doesnt tell where fat is ____________

Groups for which BMI may not correlate with fat:

Athletes Pregnant and Lactating Women People Over 65 Canadian BMI Catergories

Underweight BMI < _____________

Healthy weight BMI ____________________

Overweight BMI _________________________

Obese BMI > _____________

Body Composition Body mass is made up of:

fat, muscle, bone & organs

essential fat: men 5%; women 12% - bone marrow, CNS, internal organs

Healthy % body fat: men 12-20%; women 20-30%

Risks from UnderweightBody fat: essential in manufacture of hormones; required component of every cell in the body and provides a cushion for internal organs.

Low body fat levels:

delayed physical maturation during adolescence

infertility

accelerated bone loss

problems that accompany starvation

threatens survival during famine or wasting diseases

Underweight BMIs below 18.5 kg/m

Underweight caused by: genetic tendency to be thin; Poverty ; Illness or voluntary restriction of food intake.

Underweight in developed nations results from illnesses such as: HIV/AIDS, pneumonia, Cancer ,

anorexia nervosa, restriction of food

Poverty

Some people underweight for height have healthy body composition

Unless health is compromised (fatigue, frequent illness, impaired concentration, apathy, or extreme intolerance to cold), there is little reason for concern about underweight.

Concerns with Underweight Below certain threshold may experience: Infertility; Depression; Abnormal hunger regulation; Unable to keep warm; Nutrient deficiencies or death Obesity Trends among Canadians (take your own notes here)

Risks from Overweight

Risk of dying increases proportionally with ____________________.

70% of obese people have at least one additional health problem

1. diabetes

2. hypertension

3. stroke

4. ______________5. ______________6. ________________ 7. certain types of cancer

8. arthritis

9. complications in pregnancy

Fat Distribution

- intra-abdominal obesity visceral fat

- central obesity

Excess fat in the chest and stomach areas (Apple-Shaped) = higher risk for diabetes, heart disease and hypertension than excess fat in the hips, thighs, and buttocks (Pear-Shaped).

Measures of Body Composition and Fat Distribution

1. Anthropometry

Fat Fold tests Use caliper to gauge thickness of a fold of skin on back of arm, sub sca, chest, abdomen Waist circumference Indicatior of fat distovution and abdomina fat

Women > 88 cm

Men >102 cm2. Density

Underwater Weighing3. Conductivity

Bioelectrical Impedance Radiographic techniques

4. Dual energy X-ray absorptiometry (DEXA)

use low dose x-ray absorption to measure lean and fat mass Measurement of Abdominal Fat

Waist circumference

Women >________ cm; Men >_________ cm (higher risk of central-obesity diseases)

How Much Body Fat Is Ideal?

Man of normal weight: ________________

Overfat: greater than 22%; 25% if over 40 years

Female of normal weight: ______________

Overfat greater than 32%; 35% if over 40 years

The Mystery of Obesity

Causes of obesity are complex

Influences on obesity are multiple

1. Diet

2. Physical inactivity3. Environmental exposures

4. Genetic factors

5. Socio-economic status

Genetics and Obesity Single gene mutations are rare Few genetic differences are known to cause obesity Most people have an inherited tendency to obesity which is compounded by poor lifestyle choices

Obesity rates have greatly increased yet human genome has remained relatively constant

Physical Inactivity and Obesity

Fitness of Canadian adults has declined since 1980s (Tremblay, 2009)

Low activity relates to obesity

All activity has become voluntary Physical activity traded for time, convenience and personal fat stores

TV watching and computer use (Fulton, 2009)

Active lifestyle = walking 1hr/d

External Factors Promoting Obesity

Variety of delectable foods

Emotions (loneliness, cravings, depression etc.)

Time of day

Stress

High calorie, inexpensive foods

Advertising

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