Understanding Body Fat
The most important information obtained from monitoring % body fat is determining changes in muscle tissue over time. By determining body fat % the mass of the muscles, organs and bone can also be calculated.
- Can be used as a general indicator of health.
- It is natural for women to have a higher body fat percentage than men.
The following figures are a classification of what is regarded as generally acceptable levels of percentage fat in healthy individuals:
- Average Female 17 - 28%
- Average Male 12 - 21%
This is considered a more accurate measure of fat % and obesity than height-weight ratio. Skinfolds at multiple sites generally provide a more accurate indication so, to achieve accuracy, it is best to take three measurements at a site and then record the average figure. Sites frequently measured include:
- Abdomen - measure on a vertical fold around 1 inch (2.5cm) right of the belly button).
- Calf - measure on the inside right calf at the level of the maximum calf girth.
- Thigh - measure mid way between the knee cap and the point at where the hip joint bends in the front ...take a vertical skin fold.
- Triceps - measure a skin fold on the upper arm, mid way between the shoulder and the upper arm.
- Scapula - measure on right side of the body 1.25cm below inferior angle of scapula following natural lines of the fold.
- Suprailiac measure a diagonal fold at the front of the hips just above the crest of the ilium.
Height needs to be measured in bare feet with the individual standing erect with heels flat on the floor. Tables suggest the range a person falls into according to their height and weight. An individual may be only 160 cm tall however her weight is 70 kgs. A standard table would categorise her in the overweight range. Her ideal weight for her height is said to be about 58 kgs. This method is not very accurate because it does not take into consideration her bone or muscle weight. This girl may be an elite body builder or shot putter. She may have a larger proportion of muscle compared to an average 160cm tall female. Muscle weighs more than fat therefore she cannot really be classified as overweight or obese. Such height/weight tables should only be used as a general guide.
Body Mass Index (BMI) is a frequently used formula to determine obesity.
Body Mass Index = Body Weight(kg) divided by Height (in metres) squared
BMI is related to body composition. It takes into consideration physiological variables such as height, whether you body frame is large, medium or small, and your body type (i.e. tall & lean, short & muscular). It provides a better estimate of obesity than body weight. It is highly correlated with relative body fat. Most medical professionals, nutritionists, and specialists use BMI.
Utilising the formula above lets say a man weighed 104 kgs and is 183 cm tall. This would be 104kgs divided by 1.832. He would have a BMI of 32 kg per m2 and is considered obese.
The normal healthy range for BMI is 20-24. A BMI below 20 is considered underweight. A BMI of 25-30 is considered to be overweight, and one of 30-34 considered as obese. Above 35 is morbidly obese and people who fall in this category, or are close to it, you really need to seek out information on the secondary health issues related to the obesity (can be physical; such as joint problems, mobility issues, or physiological; such as hormonal imbalances, circulatory problems in the extremities, metabolic disorders). Obese people are at higher risk of heart conditions, high blood pressure and stroke as well as some cancers. You will also need to ensure the equipment you use can hold the weight of a morbidly obese client and be sure not to overexert them.
Article by Staff of ACS Distance Education
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