Anthropometric assessment of body composition


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Lecture on body composition, particularly focused on skinfold measurements

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  • There is an increasing emphasis on the assessment of both the amount of body fat and its distribution: the amount of intra-abdominal visceral fat often correlates significantly with metabolic disturbances that can be linked to the risk of cardiovascular disease
    BMI is an estimate of body fat
    Waist-hip circumference is a surrogate for intra-abdominal visceral fat
    Skinfold thickness determinations, either alone or in association with limb circumference measurements, are frequently used to estimate the percentage of body fat
  • Anthropometric assessment of body composition

    1. 1. Anthropometry measurements
    2. 2. Why anthropometry? Fast and cheap means in clinical diagnostics: - growth problems - overweight in children - malnutrition Important in assessing health of populations: - screening - health surveillance - epidemiologic studies
    3. 3. Advantages • Anthropometric measures are indicators of  past exposures (e.g. past malnutrition leads to low height)  future events (e.g. high waist circumference is a risk factor for cardiovascular diseases) • fast • simple • non-invasive • relatively cheap
    4. 4. Limitations Relatively insensitive towards distrubances in nutritional status over short period of time Impossible to detect specific nutrient deficiency Protein deficiency? Nutrient deficiency? (e.g. Zinc) Stunted child Energy deficiency?
    5. 5. Two types of anthropometric measurements 1. Measurements that assess body size Height Head circumference Knee height Arm span Elbow breadth Weight 2. Measurements that assess body composition - measurements of body fat (Skinfold thickness, BIA, waist) - measurements of fat-free mass (BIA, Densitometry)
    6. 6. Height In children: •Indicator of stunting: insufficient growth because of nutritional deficits •Needed to calculate indices of body composition: e.g. BMI, waist-height-ratio In adults: •Needed to calculate indices of body composition: e.g. BMI, waist-height ratio
    7. 7. Equipment 1. Stadiometer 2. Microtoise
    8. 8. Sequence 1. Person should be > 2 years old 2. Person should wear only light clothes, no shoes and no socks 3. Person steps on Stadiometer • Feet together and flat on the floor • Knees straight • Heels, buttocks and shoulder blades in contact with vertical surface of the stadiometer/wall • Shoulders relaxed, palms facing thighs • Head not necessarily in contact with the vertical surface and in Frankfurt Plane
    9. 9. Frankfurt plane
    10. 10. 4. Subjects are asked to take a deep breath and stand tall to help straightening the spine 5. Lower headboard and press down the hair 6. Measure taken at expiration 7. Eye of examiner on level with headboard
    11. 11. Time of day Height decreases during the day due to compression of the spine  Always note the time of the day and try to measure at the same time of day for all subjects or when doing repeat measurements
    12. 12. Waist circumference • Measures abdominal fat (subcutaneous + intraabdominal). • Excess abdominal fat is associated with risk of cardiovascular and metabolic disorders. • Greatly increased risk: Men: > 102 cm Women: > 88 cm • Waist-hip ratio: According to WHO. Applies to adults. Men: < 1.0 Women: < 0.85 • Waist-height ratio: Waist/height should be less than 0.5 (Adults and children)
    13. 13. How to measure waist circumference • The patient should stand straight, relaxed, with the arms at the sides and feet together pointing forward • Find the iliac crest and mark with pen • Find the lowest rib margin and mark with pen • Measure the distance between the marks and mark the middle • Face the patient and place the tape horizontal at the middle mark. Make sure it is horizontal all the way around • Measure at the end of a gentle expiration. Measure to the last completed unit (the last line you can actually see on the tape)
    14. 14. Sources of error • Patient could have problems standing still or be very ticklish. • Difficulty in finding the iliac crest or lowest rib margin. • Patient could intentionally depress abdomen. • Measuring waist is practical but needs practice and standardization.
    15. 15. Sagittal diameter Measures abdominal fat. The distance between the examination table and the highest point of the abdomen in the supine position Less studied than waist circumference Men < 22 cm Adults Women < 20 cm Sagittal Abdominal Diameter as a Screening Tool in Clinical Research: Cutoffs for Cardiometabolic Risk. J Obes. 2010; 2010: 757939.
    16. 16. Two types of anthropometric measurements 1. Measurements that assess body size Height Head circumference Knee height Arm span Elbow breadth Weight 2. Measurements that assess body composition - measurements of body fat (Skinfold thickness, BIA, waist) - measurements of fat-free mass (BIA, Densitometry)
    17. 17. Fat and fat-free mass FAT MASS ~26.9% (women), ~ 14.7% (men) Mineral Protein FAT-FREE MASS Water e.g. BMI, Densitometry (BodPod, Underwater-weighing), Skinfold Thickness, BIA, waist-hip ratio
    18. 18. Indices Often not raw measurements are used but indices: •Body Mass Index (weight/height2), •Waist-Hip-Ratio •Waist-Height-Ratio •Mid-upper-arm muscle circumference (mid upper arm circumference – π*triceps skinfold thickness) •Growth indices: head circumference for age, weight-for-age, weight-forheight, height-for-age
    19. 19. Skinfold thickness Skinfold thickness measurements provide an estimate of the size of the subcutaneous fat depot, which in turn, provides an estimate of total body fat Such estimates are based on two assumptions: – The skinfold sites selected for measurement, either singly or in combination, represent the average thickness of the entire subcutaneous adipose tissue – The thickness of the subcutaneous adipose tissue reflects a constant proportion of total body fat Neither of these assumptions is true, in fact: – The relationship between subcutaneous and internal fat is nonlinear and varies with body weight and age (not valid in obese people) – Variations in the distribution of subcutaneous fat occur with sex, race or ethnicity and age
    20. 20. Measurement sites (1) The most commonly used sites are: – Tricepts skinfold (1): Mid-point of the back of the upper arm – Bicepts skinfold: Front of the upper arm, above the center of the cubital fossa – Subscapular skinfold (2):below and laterally to the (2) angle of the shoulder blade, with the should and arm relaxed. The skinfold should angle 45º from horizontal, in the same direction as the inner border of the scapula – Suprailiac skinfold (3): mid-axillary line superior to the iliac crest. Picked up obliuquely just posterior to the midaxillary line and parallel to the cleavage lines of the skin – Midaxillary skinfold: picked up horizontally on the midaxillary line, at the level of the xiphoid process (3)
    21. 21. Calipers Skinfold thickness measurements are best made using precision thickness calipers, they measure the compressed double fold of fat plus skin Three types of precision calipers can be used: Harpenden (a), Lange (b) and Holtain (c) Designed to exert a defined and constant pressure throughout the range of measured skinfolds and to have a standard contact surface area The subject should stand erect with feet together, shoulders relaxed and arms hanging freely at the sides There is no consensus as to whether the left or right side of the body should be used
    22. 22. Step by step skinfold measurement • Generally the measure is done on the left side of the body • Identify the measurement site and mark it with a pencil • Keep the caliper in the right hand and pitch the skin with thumb and index fingers, avoiding pinching the muscle • Pinch the skinfold with the caliper • Read the measurement on the caliper • Open and remove the caliper • Repeat twice (with at least 2 minutes interval) • If the second measure differs by more than 10% from the first, repeat a third time
    23. 23. Limitations in measurement Intra-observer variation: Occurs when an examiner fails to obtain identical results on repeated measurements on the same subjects Influenced by: measurement site, the experience of the examiner and can be reduced by a proper training
    24. 24. Limitations in measurement Inter-observer variation: Occurs when two or more examiners measure the same subject and site and get different results usually larger than intra-observer variation can be reduced with training and care
    25. 25. Assessing body fat with multiple skinfolds No single region of the body can be considered representative of the whole subcutaneous fat distribution The optimum combination of skinfold measurement sites for assessing subcutaneous fat and, by inference, total body fat has not been extensively investigated, also considering the different fat distribution among different people When estimating body fat, multiple skinfolds are therefore particularly advisable and generally the mean measurement between multiple skinfolds is used
    26. 26. Electric field Leg Trunk Arm Bio-impedance Bioimpedance analysis is based on the measurement of resistance of the human body to the passage of an alternating current at a fixed frequency of 50 kHz This is done transcutaneously, via two surface electrodes (called primers) Generator voltmeter A second pair of electrodes (called sensors) has the task of recording the resistance of the body to the passage of current. This opposition to current flow is called impedance (Z). The impedance consists of two components: resistance and reactance
    27. 27. Fat-mass determination with modern scales Many modern scales give a measurement of body fat-mass and water This must be considered only an estimation, also because not all of the scales are equipped with handles in order to measure whole body resistance The estimation of body water is not proportional to liquid retention as many firms reports, since this technique is totally unable to distinguish between IC and EC water as BIA
    28. 28. Thanks!