HPN2010 - Lectures 5-7

The measurement of indicators of dietary status and nutrition-related health status of individuals or populations to identify the possible occurrence, nature, and extent of impaired nutritional status.

The systematic process of collecting and interpreting information in order to make decisions about the nature and cause of nutrition-related health issues that affect an individual

• Identifying persons at nutritional risk
• Overweight/obesity
• Determining what type of nutritional intervention may be appropriate to alter nutritional status
• Monitoring the effects of nutrition intervention
• Schools

The end result of the utilization of energy by the body, says whether the particular individual is normally nourished, undernourished, over-nourished, or whether s/he has an imbalance of nutrients.

• Desirable
• Under-nutrition
  • Depleted nutrient stores
  • Reduced biochemical functions
  • Clinical signs and symptoms
• Over-nutrition
  • Excess intake
  • Obesity
  • Use of vit. & min. supplements

• Anthropometrics
• Biochemical
• Clinical
• Diet History

Nutrition assessment is the interpretation of information from Anthropometric, Biochemical, Clinical, and Dietary studies

• measurement of body size, weight, and proportions
• considered the method of choice for estimating body composition in a clinical setting

• Weight
• Length
• Height
• Arm Circumference
• Head Circumference
• Chest Circumference
• Skin-folds

• Obtained using an electronic scale or balance-beam scale with non-detachable weights.
• Scales should be placed on a flat hard surface.
• Subject should stand still in the middle of the scales.
• Weight should be read to the nearest 0.1kg.
• Ideally, children and adults should be weighed after voiding and dressed in light clothing.

Identify weights associated with good health and longevity.

1. Weight within the suggested range for height.

2. Fat distribution at low risk of illness and premature death.

3. Medical history without risk factors of obesity: blood pressure, blood cholesterol, etc.

• Overweight is defined as body weight above some reference point of acceptable weight that usually is defined in relation to height.

• Obesity is defined as an excess of body fat in relation to lean body mass.
• Obesity is a condition of abnormal or excessive fat accumulation in tissues to the extent that health may be impaired

IBW males (kg) = 48 + (height (cm) – 152) x 1.06

IBW fem (kg) = 45.4 + (height (cm) – 152) x 0.89

• Length and stature are measured in the Frankfort horizontal plane position.
• Length is obtained with the subject lying down and is generally reserved for children less than 24 months.
• Standing height can be measured for subjects 2 to 3 years of age and older who are able to stand without assistance.

• Measuring length in children
• Frankfort horizontal plane position
• measuring height in a standing position

Several approaches to determining frame size have been proposed:

• Biacromial breadth (distance between the tips of the biacromial process at the top of the shoulders)
• The ratio of the stature to the wrist circumference
• The breadth of the chest based on chest X rays
• Knee and wrist breadth
• Elbow breadth

• estimate frame size.
• Elbow width/breadth is measured as the distance between the bony protrusions of the elbow.
• Procedure:

1. Right arm is raised to the horizontal

2. Elbow flexed to 90 degrees.

3. Back of hand must face measurer.

refer to elbow breadth photo

• issued by nutrition authorities or insurance companies are often used to assess the weight status of individuals of different ages and sex.
• Frame size is often considered in these tables.
• They are not very accurate as an assessment too

• A.K.A: Weight-for-age growth charts
• often used with infants and toddlers to assess the development

Growth charts are used to evaluate growth in infants

– appropriate chart is selected

– based on age and sex

Growth charts

• Height and weight correspond to a percentile
• 50th percentile is considered average

• > 95th percentile = Overweight
• 85th to < 95th percentile = Risk of overweight
• < 5th percentile = Underweight

reference; baby book charts

• Muscle, bone, fat, and tissue make up a person’s body weight.

Bodyweight = fat + lean tissue (including H2O)

• A person’s weight does not accurately represent their body composition.

Measuring body fat:

• Skinfold thickness
• Underwater weighing (most accurate)
• Bod Pod
• Bioelectrical impedance
• High-tech methods

This measures body density (body weight divided by volume): the denser the body, the more lean mass there is.

• Procedure:
  • To measure underwater weight, the individual must sit on a scale, expel the air from the lungs, and be completely submersed and lowered into a tank/tub/pool of water.

Accurate, but requires special equipment and is not suitable for small children and frail adults.

Measures body density (body weight divided by volume): the denser the body, the more lean mass there is.

• Uses air displacement instead of water displacement to measure body volume.
• When a subject enters a chamber of known volume, the subject’s body volume is equal to the reduction in chamber volume.
• Accurate, but requires very expensive equipment which is not widely available.
• Procedure:
  • The person is first weighed. Then person sits in the pod for a few minutes, whilst breathing normally, remaining still, and keeping their hands in their lap to measure body volume. 

• This estimates body fat by measuring the rate of electrical current flow through the body.
• Only lean tissue and water conduct electrical current; fat is a poor conductor of electricity; it offers resistance to (impedes) the current.
• The percentage of the body that contains water and allows current flow is estimated. The remainder is assumed to be body fat.
• Accurate, but temporary changes in body water content can affect repeated measurements.
• Safe, convenient, portable, and non-invasive.
  
• Procedure:
  • 1. Measurements are done when:- the GI tract and bladder are empty- body dehydration is normal (e.g. not after strenuous exercise, caffeine/alcohol use)
  • 2. Electrodes are placed on the hand and feet or a person stands on a metal plate.
  • 3. A painless energy electrical current is directed through the body.
  • 4. The rate of current flow is measured.

Magnetic Resonance Imaging (MRI):

• Uses magnetic fields to create an internal body image.
• Can accurately estimate the amount of muscle mass and regional fat distribution.
• Uses no radiation – makes it safe to use, non-invasive

measure the thickness of a fold of skin in various locations of the body:

• triceps: area over muscles on the back of upper arm
• biceps: area over biceps muscle – front of upper arm
• subscapular: below and lateral to the bottom tip of shoulder blade in a 45 degrees angle
• suprailiac: at side of waist, 1 cm above the anterior superior iliac.

These tests measure subcutaneous fat which is assumed to reflect total body fat and indicate fairly accurately fat location.

Procedure:

1. Fatfold/skinfold measures are taken using special calipers and in triplicate. (The mean is then calculated).

2. They are taken on the right hand side of the body.

• Measures taken from central-body sites better reflect changes in fatness than measures from upper sites.
• Fatfold/skinfold measures provide accurate estimates of body fat in normal-weight individuals but are difficult to perform and less accurate in obese subjects.

• depends on the individual person.
• Women naturally have more body fat: 18-31%.
• Men may have 10-25% body fat.
• Athletes need less body fat.
• Health risks of being obese apply to people who are overfat:
  • Men >25% body fat
  • Women > 30-35% body fat

A person should have enough body fat to meet basic needs but not too much to incur health risks.

• Body fat distribution is an important concept in considering the health implications of obesity.
• Body fat distribution can be classified into two types:
  • Android
  • Gynoid

• Disease risk is associated with upper-body placement of fat.
• Fat distribution is a more important risk factor for morbidity and mortality than obesity per se.
• The presence of increased total abdominal fat is an independent risk predictor, even when BMI is not markedly increased.
• Visceral adiposity is associated with incident cardiovascular disease and cancer

• A simple ratio of weight-for-height is commonly used to classify overweight and obesity in adults.
• It is calculated by dividing the weight in kilograms divided by the square of the height in meters.
• BMI is age-independent and the same for both sexes
• BMI is an indicator of body fatness and should be used in conjunction with other measures of fat distribution e.g. waist circumference.

Classification                             BMI (kg/m²)                             Risk of comorbidities

Underweight                                     <18.5             Low(but risk of other clinical problems increased)

Normal Range                                18.5-24.9                                            Average

Overweight                                       >/25.0                             

Pre-obese                              25.0-29.9                                          Increased

Obese Class 1                       30.0-34.9                                          Moderate

Obese Class 2                       35.0-39.9                                           Severe

Obese Class 3                          >/40.0                                         Very Severe

BMI (kg.m²) cut-offs                                 Nutritional Status

  >40.0                                                     Very obese

30.0-40.0                                                     Obese               

25.0-29.9                                                 Overweight

18.5-24.9                                                     Normal

17-18.49                                      Mild chronic energy deficiency

16-16.9                                   Moderate chronic energy deficiency

<16.0                                        Severe chronic energy deficiency

• BMI values have 2 major disadvantages.  They give no indication:
  • how much of the weight is fat.
  • where the fat is located.
• BMI values are unsuitable for use with:
  • Athletes
    • because their highly developed musculature falsely increases their BMI values
  • Pregnant and lactating women
    • because their increased weight is normal during childbearing
  • Adults over 65
    • because BMI values are based on data collected from younger people
    • because there is a decrease in stature (people “grow shorter”) with age.

• Traditionally used as an indicator of visceral fat.
• The waist circumference is divided by the hip circumference.

If the WAIST-HIP RATIO is:

• greater than 1.0 in men
• greater than 0.8 in women

it indicates more visceral fat storage.

• Waist circumference is an indicator of visceral fatness.
• It is a valid indicator of visceral fat for both men and women.

Procedure:

• Waist measurements should be taken in duplicate or triplicate and the average than used
• Standard cut-off points are:
  • Men: 94 cm (indicating a BMI > 25)
  • Women: 80 cm (indicating a BMI > 25)
  • Men: 102 cm (indicating a BMI > 30)
  • Women: 88 cm (indicating a BMI > 30)
• Waist circumferences above these standard cut-off points raise the risk for certain obesity-related diseases (even for those with normal-range BMIs).

• The objective with high specificity & sensitivity
• Measures many variables of nutritional significance (Ht, Wt, skinfold thickness, waist & hip ratio & BMI).
• Readings are numerical & gradable on standard growth charts
• Readings are reproducible.
• Non-expensive & need minimal training