Body Mass Index | How is Calculated (BMI) | LYGOS 2024

Body Mass Index

Body mass index (BMI) is a simple but effective measurement used to assess an individual’s weight for height. BMI is weight (in kg) divided by height squared (in meters) and is generally considered an indirect indicator of body fat percentage. This calculation plays an important role in determining whether a person is at risk of obesity. The BMI value helps the individual understand how close they are to their ideal weight and provides a roadmap towards a healthy lifestyle.

What is Body Mass Index?

Body mass index, also known as BMI, or height-weight index, is a value calculated by dividing an individual’s weight (kg) by the square of their height (in meters) (BMI=kg/m²). This calculation is widely used to determine a person’s risk of obesity, based on the World Health Organization’s classification of obesity. However, BMI only provides an assessment based on the ratio of height and weight, so it does not provide direct information about the distribution of body fat.

In general, BMI is a practical tool for assessing whether an individual is at an ideal weight. However, it is necessary to correctly interpret what the results mean. The most important purpose of BMI is to determine whether an individual is at a healthy weight and to detect obesity. Therefore, it may be necessary to consider BMI only as a starting point and to use more comprehensive methods to assess overall health status.

How is Body Mass Index (BMI) Calculated?

Body mass index (BMI) is a measure of a person’s weight in meters divided by the square of their height in meters (kg/m²). This calculation is often used to assess whether an individual is at a healthy weight. By providing an index value based on a person’s height and weight, BMI provides an estimate of the potential risk of obesity and the proportion of body fat in the body.

The formula for calculating body mass index is quite simple: A person’s weight (kg) is divided by the square of their height (meters). This shows whether the person is within the ideal weight range and provides an important indicator for a healthy life. For example, obesity or overweight can be easily detected with BMI, allowing individuals to make more informed decisions about weight management.

For example, the BMI of a person who weighs 70 kilograms and is 1.75 meters tall can be calculated as follows:

• BMI = 70 / (1.75 x 1.75) = 22.86
• Results below 18, 5 kg/m²: Below ideal weight
• Results between 18.5 kg/m² and 24.9 kg/m²: Ideal weight
• Results between 25 kg/m² and 29, 9 kg/m²: Above ideal weight
• Results between 30 kg/m² and 39, 9 kg/m²: Above ideal weight (obese)
• Results over 40 kg/m²: Much above ideal weight (morbidly obese)

What Should Body Mass Index Be?

Body mass index (BMI) is an effective method used to assess the risk of obesity, providing a general idea of an individual’s body weight and fat percentage. The results obtained by calculating BMI play an important role in determining whether a person is at a healthy weight. These values help the individual to understand whether they are in the ideal weight range or not, while also indicating possible overweight or underweight.

The BMI values obtained as a result of the calculation are divided into different categories and each category provides information about the health status of the person. For example, BMI values within a certain range indicate an ideal weight, while higher results indicate a risk of obesity or overweight. BMI is a simple but effective tool that individuals can use to monitor their health status and take precautions against potential health problems. So, what should body mass index be?

• 18.5 and below: Weak
• 18.5 – 24.9: Normal weight
• 25.0 – 29.9: Overweight
• 30.0 – 34.9: Obese (1st degree obesity)
• 35.0 – 39.9: Extremely obese (grade 2 obesity)
• 40 and over: Morbidly obese (grade 3 obesity)

Body Mass Index By Age

Body mass index (BMI) by age may change over time. In line with the standards set by the World Health Organization, ideal BMI ranges have been determined for each age group. These values, which differ according to age, help to assess whether the person is at a healthy weight.
For example;

• The ideal BMI range for individuals between the ages of 19-24 should be between 19-24.
• In the 25-34 age group, this range increases slightly to 20-25.
• For people aged 45-54, the healthy BMI value is 22-27.
• In the -55-64 age group, it is accepted in the range of 23-28.
• In individuals aged 65 and over, the ideal BMI value is slightly wider and determined as 24-29.

These ranges are an important guide in health assessment, taking into account the natural changes that occur in body structure with age.

Body Mass Index for Men and Women

Ideal weight refers to the body weight of individuals that is considered healthy for their age, gender and height. A person’s ideal weight may vary depending on factors such as age, gender and height. One of the most commonly used methods to determine this ideal weight is the body mass index (BMI) measurement. So, what is the ideal body mass index for men and women?

The ideal BMI range for men varies between 20-25. For women, the body mass index is considered to be between 19-24. In individuals over 50 years of age, an evaluation is made by adding 2 units to these values. For example, the healthy BMI range for men over 50 is considered to be 22-27. The calculation of the height-weight index is an important factor in the correct assessment of these ranges and this calculation will be detailed in the following questions.

Having an ideal weight positively affects the general health status of individuals and plays an important role in protection against diseases. It is also known that people who are at an ideal weight have stronger immune systems. For children, however, this assessment is based on different rules and different criteria should be used for their ideal weight.

Child Body Mass Index

There is no definitive BMI classification for children and adolescence as there is for adults. Different approaches are used to define overweight and obesity in this age group. One of the most common methods is classification based on percentile and z-score values:

Obesity in children is classified according to the most recent references of the World Health Organization (WHO). For example, overweight in children under 5 years of age is considered to be >+2 SD or above the 97th percentile according to the z score. Obesity is defined as >+3 SD or above the 99th percentile. In the 5-19 age group, overweight is defined as >+1 SD or above the 85th percentile and obesity is defined as >+2 SD or above the 97th percentile according to the z score.

These classifications are critical for monitoring the health status of children and young people and providing an opportunity for early intervention against obesity. Proper weight control during childhood is considered a major step towards reducing health risks later in life.

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Body Mass Index FAQ
(Frequently Asked Questions)