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Body Composition and Weight Control

Body Composition and Weight Control. Learning Outcomes. Describe various methods to measure body composition to include: densitometry, skinfold thicknesses, bioelectrical impedance analysis, body mass index (BMI), waist/hip ratio, mid-upper arm circumference;

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Body Composition and Weight Control

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  1. Body Composition and Weight Control

  2. Learning Outcomes • Describe various methods to measure body composition to include: densitometry, skinfold thicknesses, bioelectrical impedance analysis, body mass index (BMI), waist/hip ratio, mid-upper arm circumference; • Describe the limitations of the above methods; • Explain the importance of differentiating between “overweight” related to large muscle mass or bone mass and that due to excess fat.

  3. Learning Outcomes contd. • Describe the problem of rising incidence of obesity in the UK; • Describe possible causes and possible treatments of obesity; • Explain the place of exercise in increased energy expenditure as part of weight-control programmes; • Describe the effect of frequency, intensity, duration and type of exercise on body composition and weight control.

  4. Body Composition • Measuring body weight does not distinguish between weight of fat and weight of muscle. • Body composition = ratio of fat: lean tissue • % body fat presenting least health risk = 18-25% in women and 13-18% in men. • Assumes two main compartments: fat mass and fat free mass. • There are several different ways of measuring body composition.

  5. Densitometry • Measurement of body density by underwater weighing. • Density = weight/volume. • Body density measurement can predict relative proportions of lean and fat tissue. • Lean tissue weighs more underwater. • %fat = 495/density(g/cm³) – 450 • Very accurate. • Requires specialised equipment and the need to be submerged may cause anxiety.

  6. Skinfold Thickness • Most common method of % of body fat in the body. • Uses skinfold callipers to measure layers of fat under the skin at specific sites. • These measurements are then used to estimate the percentage of fat in the whole body. • Non-invasive, cheap, portable, quick, accurate. • Takes practice, doesn’t account for unusual fat distribution, difficult in very obese or very lean individuals.

  7. Bioelectrical Impedance Analysis • Small electric current passed through the body and electrical resistance is measured. • The greater the resistance the greater the % body fat. • Easy to use, quick, portable, requires removal of a sock only. • Hydration levels and skin temp will affect accuracy.

  8. Body Mass Index (BMI) • Calculated by dividing body weight/height squared. • Used to tell if someone is overweight and assess risk to their health. • Easy to calculate • Individuals may be classed as overweight when additional weight is due to fat free mass.

  9. Waist:Hip Ratio • Two distinct patterns of fat distribution – “apple” and “pear”. • Distribution of fat can be calculated by waist:hip ratio. • “At risk” values are ratios greater than 1 for men and 0.8 for women.

  10. Weight control and obesity • Obesity is rising in the UK: 16% men and 18% women are obese (BMI>30). • In Scotland >20% of population are obese with trend rapidly rising among children. • Health risks include: CHD, Type 2 diabetes, some cancers, bone and join disorders, respiratory problems.

  11. Weight control and obesity • Causes are often complex and interrelated. • Environmental, genetic, psychological, metabolic and dietary factors all involved. • Steep rise mainly due to decrease in physical activity and increase in energy-dense (high fat) diet. • Treatment – must include reduced energy intake and increased energy expenditure.

  12. Effect of Exercise on Body Composition and Weight Control • Weight reduction regime most effective if it includes both increased activity and reduced energy intake. • Activity must be regular and strenuous enough increase HR by 55-70% of maximum.

  13. Effect of Exercise on Body Composition and Weight Control • Some benefits of regular exercise include: • Increased muscle:fat ratio • Increased BMR (basal metabolic rate) • Increased Energy Expenditure (EE).

  14. Typical Essay Question • Describe methods available for measuring human body composition and discuss the limiatations associated with each method (15marks).

  15. Useful Websites • http://www.americanheart.org/presenter.jhtml?identifier=4489 • http://nhlbisupport.com/bmi/bmicalc.htm • http://www.brianmac.demon.co.uk/fatyuhasz.htm • http://www.healthscout.com/ency/68/179/main.html

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