What is BMI and why it is important

BMI is an abbreviation of body mass index (sometimes called Quetelet index). That’s a value which is calculated by considering the height and the weight (mass) of the person. The actual definition is – body mass divided by the square of the body weight. That unit has been derived as an attempt to quantify how much tissue mass (and by tissue it’s meant fat, muscle and bone) in order for one to be qualified as underweight, normal weight, overweight or obese.

Usually a person is said to be underweight with a BMI under 18.5 km/m^2, normal weight with a BMI about 18.5-25, overweight with BMI of 25-30 or obese with BMI over 30. Additionally, the obesity is divided further into three categories – Class I (which is a BMI between 30 and 34.9), Class II (which is a BMI between 35 and 39.9) and Class III (which is a BMI of 40 and above).

The risk of various health problems (like diabetes, heart disease and others) raises progressively with a BMI which is above 21.

Usually when your BMI is below 18.5 you might be advised to eat more in order to achieve a normal weight. If you have a BMI between 25 and 30, then the doctor will advise you to lose some weight and start exercising. For a BMI above 30 BMI weight loss programs and specific diets are suggested and people are sometimes referred to a dietitian.

The formula for calculating the BMI is:
Body mass index = Weight (kg) / height (m) * height (m)

This system is devised by the Belgian astronomer, statistician, sociologist and mathematician Adolphe Quetelet. It gained popularity after the obesity in the Western countries increased. The BMI is widely used to make preliminary diagnoses although there are some other metrics which can be more helpful. Still, that’s not totally reliable assessment for each body type and isn’t the only factor which doctors consider.

BMI in children

Children can also become obese. Many factors are important for the risk of obesity in children – such as the affordability of healthy food, opportunities for physical activity, the exposure to marketing of unhealthy or healthy foods, etc.

BMI is kids is usually calculated about the age of 2-3 but here what’s taken into consideration is a growth chart – here are used not ranges but percentiles. Kids between the age of 2 and 18 fall into the category ‘overweight’ if their BMI is between 85 th -94 th percentile. With a BMI in the 95- th percentile or above the kid is considered to be ‘obese’.

Why it’s important?

If your body mass index is low this may be a signal that you may actually be malnourished due to you not getting an appropriate number of calories for your level of activity or due to improper absorption of nutrients. And if the BMI is too high this means that the risk of certain cancer types, hearth diseases and diabetes is lower than that of people with a normal body mass index.

What are the problems with BMI?

That may be one of the things doctors consider but it’s not flawless because it doesn’t account for gender (usually men have less body fat than women). It also doesn’t account for the muscle mass which weighs more than the fat. BMI also doesn’t consider the generic factors, the activity level and the bone density.

Risk factors for a high BMI

Risk factors for a high BMI are excessive body fat and a high body weight. The fat can be accumulated in the body if you consume more calories than you spend though different activities. Also, if you consume too little fruits and vegetables you may accumulate more body fat because these foods have a lower energy density than other foods. It’s also important to be active enough. If you have an injury or an illness which doesn’t allow you to be physically active you are at a higher risk of gaining weight. If you have a job where you mostly sit behind a desk you are also at risk of weight gain.

Lowering the BMI

In order to lower the BMI, you should lower your weight. You can do this by several different means.
Regular exercise. It’s recommended to have 75 minutes of high intensity aerobic exercises (jogging, running, biking or swimming) or 150 minutes of moderate intensity aerobic exercises (such as walking) per week.

Be careful with what you eat. Choose foods which are low in calories and high in fibers – for example, beans, whole grains, fruits and vegetables. For the best results you need to limit the intake of unhealthy fat, sodium and added sugars.

Manage the stress. Chronic high stress increases the risk of certain health problems which include diabetes, depression, anxiety, high blood pressure and obesity.


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