BODY COMPOSITION

BODY COMPOSITIONChapter 6

TEST YOUR KNOWLEDGEExercise helps reduce the risks

associated with overweight and obesity even if it doesn’t result in improvements in body composition. True or False?

◦ TRUE. Regular physical activity provides protection against the health risks off overweight and obesity. It lowers the risk of death for people who are overweight or obese as well as for those at a normal weight

TEST YOUR KNOWLEDGEWhich of the following is the most significant

risk factor for the most common type of diabetes (type 2 diabetes)?a) Smoking b) Low-fiber diet c) Overweight or obesity d) Inactivity

C. All four are risk factors for diabetes, but overweight / obesity is the most significant. It is estimated that 90% of cases of type 2 diabetes could be prevented if people adopted healthy lifestyle behaviors. About 18 million Americans have type 2 diabetes, and more than 6 million of those with diabetes don’t know it.

TEST YOUR KNOWLEDGEIn woman, excessive exercise and low

energy (calorie) intake can cause which of the following?a) unhealthy reduction in body fat levelsb) Amenorrhea (absent menstruation)c) Bone density loss and osteoporosisd) Muscle wasting and fatigue

ALL FOUR. Very low levels of body fat, and the behaviors used to achieve them, have serious health consequences for both men and woman.

BODY COMPOSITIONThe relative amounts of fat and fat-free

mass◦Fat-free mass: all the body’s non-fat tissues:

Bone Water Muscle Connective tissue Organ tissues Teeth

◦Body fat: Essential fat Nonessential (storage fat)

Essential fatLipids incorporated to the

nerves, brain, heart, lungs, liver and mammary glands

Crucial for the body functioning

3-5% body weight in man 8 – 12% body weight in

woman

Nonessential fatExtra fat or fat reserves stored in the bodyExists primarily in fat cells or adipose

tissueLocated below the skin and around major

organsThe amount of nonessential fat depends

on many factors: gender, age, heredity, metabolism, diet and activity level.

Overweight and obesityMuscle tissue is denser and heavier than fat, a

fit person can easily weight more than the recommended weight on a height/weight table.

For the same reason, an unfit person may weight less than the table’s recommended weight.

It is important to consider body composition – percent of body fat. ◦ Example:

2 woman 5 ‘5’’ tall weight 130 pounds One has 15% of body weight as fat The other has 34% of weight as fat None of them is overweight by most standards, but the

second woman is over-fat

Overweight and obesityOverweight: The total body

weight above the recommended range for good health◦BMI ≥ 25

Obesity: A serious degree of overweight◦BMI ≥ 30

Prevalence of overweight and obesity among Americans

Excess body fat and wellness As overweight and obesity increase, so do the problems

associated with them◦ Risk of chronic disease and premature death

Metabolic syndrome resistance to the effects of insulin, high blood pressure, high blood glucose levels, abnormal blood fat levels and fat deposits in the abdominal region.

Heart disease Cancer Hypertension Impaired immune function Gall bladder and kidney diseases Skin problems Sleep and breathing disorders Erectile dysfunction Pregnancy complications Back pain Arthritis Bone and joint disorders. Diabetes

Problems associated with overweight and obesity…

Body fat distribution and health◦Excess fat in the abdominal area

increases the risk of several diseases◦Causes are unknown but it appears

that abdominal fat is more easily mobilized and sent into the bloodstream

Problems associated with overweight and obesity…

Performance of physical activities◦Too much body fat makes

physical activity difficult

◦As a consequence, overfat people don’t exercise

◦An become less fit. They don’t have muscular strength, endurance and flexibility.

Problems associated with overweight and obesity…

Emotional wellness and self-image

◦ Being perceived as fat can cause discrimination from others

◦ Can contribute to psychological problems such as depression, anxiety and low self-esteem.

◦ The ideal body presented by the media is an unrealistic goal

Problems associated with very low levels of body fat

Having too little body fat is also dangerous

Fat is essential for the functioning of the body

Too little body fat represents◦ Less than 8-12% in women◦ Less than 3- 5% in men

Extreme leanness is linked with reproductive, circulatory and immune system disorders and with premature death.

It might also cause amenorrhea in woman and loss of bone mass.

Assessing body mass index, body composition and body fat distribution

Body mass index (BMI)◦ Measure of body weight that is

useful for classifying the health risks of body weight

◦ Based on the concept that weight should be proportional to height

◦ BMI doesn’t distinguish between fat and muscle.

◦ Calculated dividing your body weight (Kg) by the square of your height (m).

Calculate your BMIDivide body weight in pounds by 2.2 to

convert it to kilograms

Multiply height in inches by 0.0254 to convert it to meters.

Multiply the result of step 2 by itself to get the square of the height measurement.

Divide the result of step 1 by the result of step 3 to de3termine BMI.

Assessing body mass index, body composition and body fat distribution…National Institute of Health NIH guidelines

◦Consider body fat distribution and other disease risk factors in addition of BMI

◦Uses the measure of the waist circumference

Disease Risk Relative to Normal Weight and Waist

CircumferenceClassification BMI (Kg/m2) Obesity

ClassMen ≤ 40 in. (102

cm)Women ≤ 35 in.

(88cm)

> 40 in (102 cm)

> 35 in (88 cm)

UnderweightNormalOverweightObesity

Extreme Obesity

< 18,518,5 – 29,925,0 – 29,930, 0 – 34,935,0 – 39,9

≥ 40,0

IIIIII

-- --

IncreasedHigh

Very HighExtremely high

----

High Very highVery high

Extremely high

Assessing body mass index, body composition and body fat distribution…Percent Body Fat

◦Underwater weighting The individual is submerged and

weighted under water The percentages of fat and fat-free

weight are calculated from body density

Considers that muscle has a higher density and fat a lower density than water.

Overweight people tends to float and weight less under water

Lean people tend to sink and weight more under water.

Percent Body Fat◦Skinfold Measurements

Involves measuring the thickness of skinfolds at several different sites on the body.

You can sum up the skinfold values as an indirect measure of body fatness.

Measured with a device called caliper

Percent body fat◦The Bob Pod

Small chamber containing computerized sensors

Measures body composition by air displacement rather than water displacement

Determines the percentage of fat by calculating how much air is displaced by the person sitting inside the chamber

Percent body fat◦Bioelectrical Impedance

Analysis (BIA) Works by sending a small

electrical current through the body and measuring the body’s resistance to it.

Fat-free tissues, where most water is located, are good conductors of electrical current

Fat is a bad conductor. The amount of resistance to

electrical current is related to the amount of fat-free tissue in the body.

Percent body fat◦Advanced Techniques:

DEXA Dual-Energy X-Ray Absorptiometry Measures the tissue absorption of high- and low-

energy X-ray beams TOBEC Total Body Electrical

conductivity Estimates lean body mass by passing a body

through a magnetic field.

Assessing body mass index, body composition and body fat distribution…

Body fat distribution◦Waist circumference measurement

◦Waist to hip ratio calculation Divide your waist circumference by your

hip circumference

Setting body composition goals Establish a goal

Choose a target value for BMI or percent body fat

Make sure your goal is realistic: genetics limits your capacity to change your body composition.

If your body composition is close to the recommended range you might want to set a lifestyle goal rather than a specific percent body fat or BMI goal.

Set a target range for body weight

Don’t stick rigidly to a recommended body weight calculated from any formula, other factors should also be considered