What Is A Healthy Weight?

Editor's Choice
Main Category: Obesity / Weight Loss / Fitness
Also Included In: Public Health;  Sports Medicine / Fitness
Article Date: 08 Feb 2012 - 11:00 PDT


Although most of us would love to be given a straightforward solution to calculate our healthy or ideal weight, sadly it isn't that black and white. Your "healthy" weight cannot simply be calculated from a general source - people's healthy weight, or ideal weight, depends on several factors, including their age, sex, body type, bone density, muscle-fat-ratio, overall general health, and height.

Over the last few decades, using BMI (body mass index) was seen as an excellent means for calculating a person's healthy weight. However, BMI, as you will see later on in this article, is at best, a ballpark calculation with several limitations. BMI is more useful when studying large populations, rather than individuals.

Your healthy weight may be different from friends and family, often even if you are the same sex and height. You should not compare yourself to people around you, because we are all different and you run the risk of either aiming for a body weight that is too high or too low. Even comparing yourself to people outside your immediate vicinity is not ideal.

To add confusion to deciding what weight you should aim for, not even experts in different countries seem to agree. A healthy weight in the United Kingdom or the USA is slightly higher than what is set in, for example The Netherlands. If you were in Holland you would be aiming for a lower target weight than if you were in the USA.

Body Mass Index and Waist-Hip Ratio

BMI (Body Mass Index) and Waist-Hip Ratio are two ways doctors and other health care professionals gauge a person's weight, when deciding how close or far they are from a healthy one. Waist-Hip Ratio is probably more accurate (reasons later on in this article).

BMI (Body Mass Index)

This measurement is a number derived from a person's weight and height.

• BMI using Metric Units
  The person's weight in kilograms (kilos) is divided by their square of their height in meters
  - For example: Imagine a person weighs 80 kilos and is1.8 meters high.
  - 3.24 is 1.8² (their height squared)
  - 80 divided by 3.24 = a Body Mass Index of 24.69
• BMI using Imperial Units
  The person's weight in pounds multiplied by 703, divided by the square of their height in inches.
  - For example: Imagine a person weighs 190 pounds and is 72 inches (6ft) tall.
  - 5,184 = 72²
  - 190 (lbs) times 703 divided by 5184 = a Body Mass Index of 25.76

In North America, Europe and much of the rest of the world, the following BMIs point to how a person's weight is classified:

• 18.5 - underweight
• 18.5 to 24.999 - ideal
• 25 to 29.999 - overweight
• 30+ - obese
• 40 - morbidly obese

Some nations place the lower limit for "ideal" at BMI 20.

The drawback with BMI is that it does not take into account the person's measurements. For example, a super fit Olympic athlete may have the same height and weight as an unfit couch potato - they would have the same BMI. However, the couch potatoes body measurements would be completely different.


The man in this picture has the same height and weight as the man in the picture below, they have the same BMI


This person has the same BMI as the man in the picture above this one, however, this one is not overweight

People have different bone densities and body-fat ratios, BMI does not take these factors into account. An osteoporosis patient may have a lower BMI than another individual without the conditions, however, it is likely that if only BMI measurements were used, the osteoporosis patient would be deemed as healthier.

BMI has the following serious drawbacks:

• It underestimates body fat content in obese or overweight people
• It overestimates body fat content in muscular or lean individuals

Waist-Hip Ratio

Waist-Hip Ratio, also known as WHR, looks at the ratio of a person's waist circumference with their hip circumference. The smallest waist measurement is taken, which is generally just above the navel, this total is divided by their hip circumference at its widest part.


In the thinner person, the waist is measured at its narrowest point. For the fatter person with a convex waist (big belly), it is measured approx. 1 inch above the belly button. Hips are measured at the widest point of the buttocks in the lean person, and at the great trochanters in the fatter individuals

If an adult female has a 27-inch waist and 36-inch hips, her WHR is 27 divided by 36 = A WHE of 0.75

Target WHRs are different for males and femlales:

• WHR for men
  - <0.9 - means he has a very low risk of having cardiovascular health problems
  - From 0.9 to 0.99 - means he is at moderate risk of cardiovascular health problems
  - >1 - means his risk of cardiovascular problems are high
• WHR for women
  - <0.8 - means she has a very low risk of having cardiovascular health problems
  - From 0.8 to 0.89 - means she is at moderate risk of cardiovascular health problems
  - 0.9 or more - means her risk of cardiovascular problems are high

Waist-Hip Ratio versus Body Mass Index

WHR will give you a much better idea regarding how near you are to a healthy weight, compared to BMI.

Apple-shaped people have larger WHRs and tend to have a higher risk of developing diseases, such as cardiovascular problems, compared to pear-shaped individuals. An apple-shaped person has more fat built up on the waist, while the fat on a pear-shaped person has accumulated on their hips.

Females whose WHR is below 0.8 tend to be healthier and more fertile than their higher WHR counterparts. A female WHR of 0.8 means she runs a much lower risk of developing many cancers, cardiovascular disorders, and diabetes.

Males whose WHR is 9 or less have the same benefits, while those with higher WHR have similar health risks (to women in the paragraph above).

What are the drawbacks with WHR? - it still does not measure the total body fat percentage of the individual, or their muscle-to-fat ratio. However, most agree it is a superior predictor of health risks, and a better measure of ideal weight.

Measuring body-fat percentage

If you weigh a person's total fat, and divide it by their weight, you get their body-fat percentage. This measurement includes storage fat, as well as essential fat.

Essential fat is the fat we need for survival. Females have a higher proportion of their bodies made up of essential fat than men - between 2% and 5% in adult males and 10% and 13% in adult females.

Storage fat is the accumulation of fat in adipose tissue. Some storage fat also serves to protect the internal organs located in the abdomen and chest. Adipose tissue is a type of tissue that contains stored fat.

Our Total Body Fat Percentage includes both storage fat and essential fat.

According to the American Council on Exercise, male and female fat percentages should be as follows:

• Essential fat: men 2-4%. Women 10-12%.
• Total fat:
  - male athletes 6-13%, women athletes 14-20%
  - fit male non-athletes 14-17%, fit female non-athletes 21-24%
  - acceptable male 18-25%, acceptable female 25-31%
  - overweight male 26-37%, overweight female 32-41%
  - obese male 38+%, obese female 42+%

Health care professionals and sports scientists say measuring a person's body fat percentage is the ideal way of gauging their level of fitness and general health, because it is the only one that includes the person's true body composition. Quite simply, it accurately measures overweight or possible obesity in males with over 25% (body fat percentage) and females with over 31%.

A body fat percentage measurement would never make the BMI mistake of showing the athlete and couch potato with the same results.

How to measure body fat percentage?

• Air Displacement Plethysmography (ADP) - similar to the principles used in underwater weighing. In this case, air is used, hence the name. The person goes into a sealed chamber which measures their total body volume by calculating how much air was displaced. Body density is determined by combining mass (body weight) with body volume. ADP can estimate a person's body fat percentage and LBM (lean body mass).
  
  
  An athlete entering an Air Displacement Plethysmography chamber
  


• Near-infrared interactance - an infra-red light beam is sent into the person's biceps; it is reflected from the muscle inside and absorbed by the fat. This is a non-invasive technique, which experts say is safe, easy to use, and quick.
• Dual energy X-ray absorptiometry (DXA) - X-rays of two separate energies scan the body; one of them is absorbed more strongly by fat. A computer program takes the readings in one scan from the other, the difference revelas the amount of body fat there is in relation to other tissus at each point. A sum of all the points scanned is made, resulting in a reading of the person's overall body composition.

Conclusion

So, really, rather than aiming for a body weight in kilograms or pounds, we should be targeting either a WHR (waist-hip-ratio) figure or body fat percentage.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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