Body mass index (BMI)

• BMI is a common tool
• Measuring a person’s weight in relation to their height.
• BMI of less than 18.5 means that a person is underweight
• BMI of between 18.5 and 24.9 is ideal.
• BMI of between 25 and 29.9 is overweight.
• BMI over 30 indicates obesity.

Problems with BMI

• Does not consider waist or hip measurements
• Does not consider proportion or distribution of fat
• Does not consider proportion of muscle mass
• Both of which have an enormous impact on health
• Many athletes have little body fat and more muscle mass, resulting in a high BMI but this does not mean their weight is unhealthy

BMI can offer a ‘rough’ idea of whether or not a person’s weight is healthy but should not be the only measure to evaluate IBW.

Weight and Height Guide

• Determines how much a person’s weight should be related to their height.
• This measurement was a standard before BMI was designed. SEE CHART HERE.

Waist size

• Can be a measurement of health
• Health is not determined by the amount of body fat alone but also by where the fat is located.
• Fat located inside your abdomen (belly-fat) is an important risk factor for diabetes, hypertension, heart disease, fatty liver and other metabolic problems
• Fat on your hips and thighs you may think less attractive but it’s less associated with health problems.

Men

• Low risk for associated diseases – Under 94 cm / 37 inches
• Moderate risk for associated disease – 94-102 cm / 37 – 40 inches
• Severe risk for associated disease – Over 102 cm / 40 inches

Women

• Low risk for associated diseases – Under 80 cm / 31.5 inches
• Moderate risk for associated disease – 80- 88 cm / 31.5 – 34.6 inches
• Severe risk for associated disease – Over 88 cm / 34.6 inches

Problems with Waist size

• Does not accurately measure a person’s total body fat percentage
• Does not measure muscle-to-fat ratio
• Does not inform about IBW 

Waist-to-hip ratio (WHR)

• Compares waist size with that of their hips
• Higher waist measurement in proportion to hips, the greater the risk of disease
• WHR may be a better predictor of heart attacks and other health risks than BMI

How to

• Waist circumference – measure midpoint between the lower margin of the last palpable ribs and the top of the iliac crest / upper pelvic bone
• Hip circumference – measure widest portion of the buttocks, with the tape parallel to the floor
• Divide waist measurement by the hip measurement eg. 

– Waist 30″ / 76 cm
– Hips 38″ / 97 cm
– WHR = 0.78

What does it mean?

Males

• Low risk – Below 0.9
• Moderate risk – 0.9 to 0.99
• High risk – 1.0 or over

Females

• Low risk – Below 0.8
• Moderate risk – From 0.8 to 0.89
• High risk – 0.9 or above

Problems with WHR

• Does not accurately measure a person’s total body fat percentage
• Does not measure muscle-to-fat ratio
• Does not inform about IBW

Waist-to-height ratio / WtHR

• Another tool that might predict the risk of heart disease, diabetes, and overall mortality more effectively than BMI.
• Waist measurement less than half the height has a lower risk of a number of life-threatening health complications.

How to

• Divide waist size by height
• Healthy weight / IBW 0.5 or less
• 4 inches / 163cm tall, should have a waist measurement below 32 inches / 81cm
• 72 inches / 183cm tall, should have a waist measurement below 36 inches / 91cm
• The above measurements give a WtHR of just under 0.5.

Problems with WtHR

• Does not measure a person’s total body fat percentage
• Does not measure muscle-to-fat ratio

Height minus 100 = IBW

• Only works in cm and kilos
• Only really works for males (maybe females need to deduct 105 or 110
• Eg. 196 cm tall minus 100 = 96 IBW = 96 kilos
• Eg. 188 cm tall minus 100 = 88 IBW = 88 kilos

Problems with height minus 100 = IBW

• Does not measure a person’s total body fat percentage
• Does not measure muscle-to-fat ratio

 Body Fat Percentage

• Fat weight divided by total body weight
• Total body fat includes essential and storage fat.
  
  
• Essential fat
  – Necessary for survival
  – Plays a role in a wide range of bodily functions
  – Essential fat % in Men – 2 to 4 %
  – Essential fat % in Women – 10 to 13 %

• Storage fat
  – Stored subcutaneous and visceral
  – Protects the internal organs
  -Can be used for energy

• Is affected by activity levels

Athletes:
M – 6–13% / F- 14–20%
Fit non-athletes:
M-14–17% / F-21–24%
Acceptable:
M – 18–25% / F-25–31%
Overweight:
M – 26–37% / F- 32–41%
Obesity:
M 38% or more / F42% or more

How to

• Skinfold calipers
• Most common ways of measuring body fat using special calipers to pinch the skin, such as thigh, abdomen, chest (for men) or upper arm (for women).
• The techniques provide an accurate reading within around 3.5 percent
• Body Composition Analysers / Bioelectrical Impedance Analysis (my favourite)
  – A method of describing what the body is made of, differentiating between fat, protein, minerals, and body water
  – Measures body weight, fat mass, muscle mass, and body fat percentage, bone mass
  – If you live in Lanzarote book a time with me for you measurement sw@sally-walker.com

• Hydrostatic body fat measuring, or “underwater weighing”
• Air densitometry, which measures air displacement
• Body Volume Index / BVI – 3D technology analyses overall body shape, identifying where fat is distributed
• DEXA – Dual Energy X-ray Absorptiometry measures fat in the abdomen

 Conclusion

• None of the above can give a 100-percent accurate reading of IBW, but the estimates are close enough to give a reasonable assessment.
• Combining them may be the best way to get an accurate idea of whether or not you need to take action.