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Body_Composition
 

Body_Composition

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    Body_Composition Body_Composition Presentation Transcript

    • Body Composition
      • In order to determine how healthy a shape your body is in, it is more important to determine the RATIO of fat to lean tissue ( muscle, bone etc ) rather than just weight
      • This ratio of fat to lean tissue is known as body composition
      • Remember - some fat is essential for health - the problems arise when we have too much!
      • The % body fat associated with the least health risk is 18-25% for women and 13-18% for men
      • Accurate measurements are very important as % body fat greatly affects both health and athletic performance
      • Frequent monitoring of % body fat allows you to determine changes in muscle mass over time
    • Skinfold Thickness
      • Uses SKINFOLD CALIPERS to measure the thickness of the fold of skin and subcutaneous fat at one or more sites on the body
      • % body fat is frequently estimated from measurements at four locations:
            • (1) back of upper arm (tricep)
            • (2) front of upper arm (bicep)
            • (3) back below the shoulder blade (subscapular)
            • (4) waist (suprailiac)
      • These measurements are proportional to the total percentage of bodyfat
      • In general, % body fat for women > men
      • % bodyfat percentage typically increases with age for both men and women
      Takes practice to become skilled at measurement Not accurate for VERY LEAN or VERY OBESE as doesn’t take into account difference in fat distribution DISADVANTAGES Quick, cheap, relatively accurate ADVANTAGES
    • Bioelectrical Impedance Analysis
      • Method relies on fact that fat is an insulator of electricity and offers resistance or impedance to a current, while muscle tissue is a good conductor
      • A small electrical current is passed through the body and the electrical impedance is measured
      • The higher the impedance, the higher the % body fat
      Not as accurate as other methods - changes in skin temp and hydration (water) levels will affect current conduction DISADVANTAGES Quick, cheap, very easy to use ADVANTAGES
    • Densitometry
      • DENSITOMETRY (or hydrostatic weighing) relies on fact that fat is LESS DENSE than lean tissue and is based on Archimedes’ principle
      • To calculate density (g/cm 3 ) requires a persons weight and volume
      • When a body is completely immersed in water, it will displace an EQUAL volume of water
      Expensive, requires specialist equipment, individual needs to be confident underwater & therefore not suitable method for all DISADVANTAGES Extremely accurate ADVANTAGES
    • Body Mass Index (BMI)
      • BODY MASS INDEX (BMI) can determine if someone is overweight and is used to determine obesity-related health risks e.g. CHD, High B.P., Type 2 Diabetes
      • BMI values used to describe different categories of weight:
      BMI (kg m -2 ) = WEIGHT (kg) / HEIGHT (m) 2 Not accurate for persons with high levels of muscularity DISADVANTAGES Very easy to calculate ADVANTAGES
    • Waist : Hip Ratio
      • When people are overweight or obese, there are 2 distinct patterns of fat distribution:
        • The ‘Apple’ : excess fat around abdomen
        • The ‘Pear’ : excess fat over hips & thighs
      • The distribution of fat can be calculated using a simple ratio - WAIST : HIP
      • Divide the waist measurement (smallest circumference above the naval and below the rib cage) by the hip measurement (largest circumference around the bottom)
      • MEN - Ratio > 1 [Apple] / Ratio < 1 [Pear]
      • WOMEN - Ratio > 0.8 [Apple] / Ratio < 0.8 [Pear]
      • ‘ Apples’ have a greater risk of developing CHD, High B.P. & Type 2 Diabetes than ‘Pears’
      Not highly accurate DISADVANTAGES Very quick & easy to calculate ADVANTAGES
    • Mid-Upper Arm Circumference
      • Mid-upper arm circumference (MUAC) is a key indicator of the nutritional status of children
      • It is reduced substantially in the undernourished and substantially increased in children who are overweight
      • MUAC is defined as the circumference taken at the mid-point between the shoulder and elbow of the bare left arm using an insertion tape
      Not highly accurate DISADVANTAGES Very quick & easy to calculate ADVANTAGES
    • Weight Control & Obesity Obesity is a major killer Two-thirds of UK men are overweight Incidence of childhood obesity grew from 9.6% in 1995 to 13.7% in 2003
    • Costs of obesity [INFO]
      • Obesity is responsible for more than 9,000 premature deaths per year in England
      • Obesity is an important risk factor for a number of chronic diseases such as heart disease, stroke, some cancers, and type 2 diabetes
      • Incidence of obesity is rising in the UK & tackling obesity is a government wide priority
      • The Health Select Committee has estimated that the costs of obesity is £3.3 - £3.7 billion per year and of obesity plus overweight at £6.6 - £7.4 billion .
      • National Audit Office (NAO) figures - one million fewer obese people in this country could lead to around 15,000 fewer people with coronary heart disease, 34,000 fewer people developing type 2 diabetes, and 99,000 fewer people with high blood pressure
    • Analysis and Evidence Base
      • The prevalence of obesity in children aged under 11 increased from 9.9 percent in 1995 to 13.7 percent in 2003 ( Health Survey for England, 1995-2003 )
      • Prevalence has trebled since the 1980s, and well over half of all adults are either overweight or obese - almost 24 million adults. Obesity in both adults and children is more common among lower social groups
      • Obesity is the result of an energy imbalance (eating and physical activity).  Time trends show a decline in physical activity, but no significant increase in the number of calories consumed
      • Self-reported consumption has not risen significantly in the last 30 years and may well be constant or falling, and energy intake from household purchases show no significant differences from 1994-2003 ( Expenditure & Food Survey, National Diet and Nutrition Survey )
    • Possible Causes of Obesity
      • As with all obesity, any factors that cause energy intake to be GREATER than the energy expended can lead to obesity
      • Possible causes of childhood obesity include:
          • Rare genetic factors
          • Poor diet
          • Physical inactivity
    • Diet & Physical Activity
      • A trip around any major supermarket will reveal that many foods have become segregated (based on their packaging) into child-specific and adult-specific foods
      • In addition, much physical activity has been removed from the daily lives of children. The time spent in active play has been replaced by more sedentary pursuits, such as watching television and playing computer games
        • The number of primary school children who walk to and from school has fallen from 62% in 1989/91 to 56% today
        • Participation in school sport (>2 hours per week) decreased from 46% in 1994 to 33% in 1999
        • Watching television is the most popular sedentary activity for children of all ages, with over a quarter of 11–16-year-olds watching more than 4 hours a day
        • Activity levels for teenage girls are particularly low with 64% of 15-year-old girls being classified as ‘inactive’
    • Other Risk Factors
      • Other risk factors for the development of childhood obesity have not been well researched in the UK
      • Potential factors include:
          • Parental obesity
          • Time spent in inactive pursuits such as television viewing
          • Low socio-economic status
    •  
    • Effects of Exercise
      • Exercise plays a HUGE ROLE in the control of weight and body composition
      • [ N.B. Overweight or Overfat? Overweight and overfat do not always mean the same thing ! ]
      • The addition of exercise to a weight control program helps control both body weight and body fat levels by …
        • increasing muscle:fat ratio (incr. fat loss & preserving lean tissue)
        • increasing BMR (basal metabolic rate)
        • increasing energy expenditure (increasing energy output relative to input)
    • However …
      • It is important in a weight-control programme that the activity is REGULAR and STRENUOUS enough to make you breathe more heavily than normal e.g brisk walking, jogging
      • Recommended daily activity is 30 minutes of aerobic exercise, strenuous enough to increase the heart rate to between 55% and 70% of the maximum heart rate. [Remember the maximum heart rate is 220 – age]