Body Mass Index (BMI)

Body Mass Index (BMI)

The body mass index (BMI) is a physical measurement used to assess an individual's total amount of body fat. The BMI was invented by Belgian polymath Adolphe Quetelet in the 1800s, and consequently is sometimes known as the Quetelet index. The BMI is calculated by dividing your weight in kilograms (kg) by your height in meters squared (m²). It is expressed as kg/m².

What does your BMI mean?

The BMI scores give an indirect measure of body fat. Depending on the BMI value calculated you may be underweight, normal weight, overweight or obese. 

Why are BMIs useful?

The BMI is a simple, inexpensive screening tool used to identify possible weight problems for both adults and children. A BMI measurement is useful to assess who needs further testing to identify health risks such as heart disease. Individuals at risk will need further assessment. Assessments may include skin fold thickness test, diet, physical activity level, family history and other appropriate health screenings.

Risks associated with extreme BMIs

Being either overweight (with a BMI of 25 or above) or underweight (with a BMI lower than 18.5) can affect your health.

Overweight

Being overweight increases your chances of developing disease. An overweight individual whose BMI rises from 25 to 27 is 20–30% more at risk of death. As an individuals BMI rises above 27, the risk of death increases more steeply by almost 60%. If you are overweight and have low physical activity, the risks of developing disease increase.

Diseases associated with being overweight include:

• Gastrointestinal disorders;
• Cardiovascular diseases (i.e. stroke, heart attack);
• Diabetes;
• High blood pressure (hypertension);
• Osteoarthritis;
• Infertility;
• Some forms of cancer (i.e. breast, colon and endometrial cancers);
• Menstrual abnormalities;
• Gall bladder disease;
• Sleep problems;
• Respiratory problems (i.e. asthma).

Risks of being underweight

If you are underweight you may be malnourished and in addition you may develop the following nutritional deficiencies:

• Compromised immune function with increased susceptibility to infections;
• Respiratory diseases;
• Digestive diseases;
• Cancer;
• Osteoporosis;
• Increased risk of falls and fractures.

What are the limitations of the BMI?

Limitations associated with the BMI are:

• BMI varies by age, sex and race. Hence one's BMI can only be compared to those of the same sex, age and race.
• BMI does not differentiate between muscle and fat and will therefore underestimate in some and overestimate for others (e.g. An athlete may have a high BMI because of greater amount of muscle rather than fat).
• Disabled or elderly people have less muscle mass and therefore will have a lower BMI. This does not necessarily mean that their weight is normal or underweight.
• Pregnant women will also have a higher BMI because of increased weight associated with pregnancy, but not necessarily due to increased fat. BMI will overestimate body fat in this case.
• BMI does not differentiate between body fat distribution. Fat around the waist ("apple" body shape) is more dangerous than that around the hips ("pear" body shape), but this will not be picked up by the BMI.

I personally do not think BMI is very accurate, especially for someone who is active. BMI does not take into account muscle mass, and people who are active usually have a lot of muscle and even a strong build. BMI calculates the muscles as fat, making a healthy person seem unhealthy. If you know you are healthy (active and have a good diet), BMI should not matter. BMI does not account for all of the different body types, so it is common for weight statuses to be inaccurate.

Informative video about BMI:

For more information on BMI, please use these links:

http://bmi.emedtv.com/bmi/bmi-information.html

http://pcos.about.com/od/losingweight/f/BMI.htm

Resources:

http://www.healthyweightforum.org/eng/calculators/bmi-visual-graph/

http://www.dietriffic.com/bmi-chart/

http://www.medimanage.com/my-weight/articles/5-things-about-weight-loss-you-wanted-to-know.aspx

http://www.texasheartcare.org/heart.htm

http://www.virtualmedicalcentre.com/health-investigation/bmi-body-mass-index/45

http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html

http://on.aol.com/video/body-mass-index--bmi--18631016