What Is Body Mass Index? How Is Body Mass Index Calculated?

Body Mass Index is considered as a very important indicator for maintaining a healthy life. This index is a calculation method for determining the weight status of individuals and is of great importance in order to maintain a healthy life and to detect possible health problems in advance. In this article we have written for you, we will examine in detail what the Body Mass Index is, what it is calculated for and how to calculate it.

What is Body Mass Index?

Body Mass Index (BMI) is defined as the ratio of a person’s weight to the square of their height. Thanks to this index, it is evaluated whether the weight of individuals is appropriate for their height. Body Mass Index is a method used and accepted worldwide and is a criterion frequently used by health professionals.

What Is The Body Mass Index Calculated For?

Body Mass Index is calculated to evaluate the weight status of individuals. BMI shows whether the weight of individuals is ideal according to their height. In this way, individuals can have an idea about their health status and possible health problems can be detected in advance. Calculating BMI is important for assessing the risk of health problems such as obesity, heart disease and diabetes. It is also a guide for individuals to regulate their lifestyle and eating habits.

How Is Body Mass Index Calculated?

The calculation of Body Mass Index is carried out by a very simple mathematical process. First, the individual’s weight (kg) and height (m) are measured. Then, the weight value is divided by the square of the height and the BMI value is obtained. The process is as follows:

BMI = Weight (kg) / Height (m)²

The BMI value obtained is evaluated according to the categories determined by the World Health Organisation and information about the weight status of individuals is obtained. These categories are as follows;

• BMI < 18.5: Thin,
• 18.5 ≤ BMI < 24.9: Normal weight,
• 25 ≤ BMI < 29.9: Overweight,
• 30 ≤ BMI < 34.9: Obese (Class 1),
• 35 ≤ BMI < 39.9: Obese (Class 2),
• BMI ≥ 40: Extremely obese (Class 3),

Although Body Mass Index is an important tool for assessing the weight status of individuals, it is not an indicator of health status alone. Therefore, it is of great importance to be in contact with health professionals and to have regular health checks.

What Do Body Mass Index Values Mean?

Body Mass Index (BMI) is a value calculated by the ratio of an individual’s weight to the square of his/her height and helps to determine the ideal weight in terms of health. BMI values are used to assess individuals’ body fat ratios and health risks. BMI values are as follows;

• Less than 18.5, Thin,
• 18.5 to 24.9, normal weight,
• 25 – 29.9, overweight,
• 30 – 34.9, obese (grade 1),
• 35 – 39.9, obese (grade 2),
• 40 and over, extremely obese (grade 3),

Since BMI values are calculated only according to the ratio of weight and height without taking into account factors such as age, gender and muscle mass of individuals, it is not a definitive measure of health for everyone, but it provides a general evaluation.

Ideal Body Mass Index by Age

Ideal BMI values by age differ for young people, adults and the elderly. In general, body fat and BMI values increase with increasing age. Ideal BMI values are as follows;

• 19-24 years: 19-24,
• 25-34 years: 20-25,
• 35-44 years: 21-26,
• 45-54 years: 22-27,
• 55-64 years: 23-28,
• 65 years and over: 24-29,

These values represent BMI ranges that are considered healthy for age. However, individual differences and factors such as lifestyle should also be taken into account.

Body Mass Index in Children and Young People:

BMI calculations for children and adolescents are different from those for adults because they have not completed their developmental process and vary according to age, gender and growth rate. BMI assessments for children and young people are compared with other individuals of the same age and sex and expressed as percentiles. These evaluations are as follows;

• Percentile <5; Weak,
• Percentile 5-84; Normal weight,
• Percentile 85-94; Overweight,
• Percentile ≥95; Obese,

BMI assessments for children and young people are important to monitor their growth and development and to identify health risks. Families play an important role in regulating BMI values by helping their children and young people to adopt healthy living habits.

Who Cannot Use Body Mass Index?

Body Mass Index (BMI) is a value obtained by dividing a person’s weight by the square of their height. In general, it is widely used to determine a healthy body weight and fat ratio. However, there are situations where BMI is not a suitable measurement for everyone. Some situations where BMI should not be used are as follows;

• BMI is not an appropriate measurement for children and adolescents because they are still growing and developing. For this age group, doctors usually assess a healthy body weight using percentile ranking by age and gender.

• During pregnancy and breastfeeding, women’s body weight and body fat naturally increase. Therefore, BMI is not appropriate to use during these periods.

• Since BMI does not take into account muscle mass, it can be misleading for muscular individuals and athletes. In this case, body fat measurement provides a more accurate assessment.

• In older individuals, muscle mass decreases and body fat increases. Therefore, BMI may not be an accurate health indicator for the elderly.

• In people with chronic diseases, BMI may not provide an accurate assessment. In this case, doctors make an assessment taking into account the patient’s general health status and lifestyle.

Body Mass Index and Fat Ratio

Body Mass Index (BMI) and body fat percentage are two different measurements used to determine whether an individual has a healthy body weight. BMI is a value that assesses the relationship between weight and height, but does not directly measure body fat percentage. Body fat percentage is a measurement that determines how much of body weight is fat.

While BMI is generally used to determine a healthy body weight and fat ratio, it can be misleading in some cases. For example, muscular individuals may have a high BMI, but this does not necessarily mean that they have an unhealthy body fat percentage. Therefore, measuring body fat ratio along with BMI provides a more accurate assessment.

How Is Waist Circumference Measured?

Waist circumference measurement is an important measurement used to assess the distribution of body fat and determine health risks. Step-by-step instructions on how to measure waist circumference are as follows;

• Use a flexible and straight tape measure to measure.

• Stand upright with your feet hip-width apart.

• Place the tape measure under your ribs and just above your belly button. The tape measure should lie horizontally around the waist.

• Breathe in and out normally and take the measurement without pulling the tape measure tightly.

• Note your waist circumference measurement and evaluate it according to the guidelines set by health professionals.

Waist circumference measurement can be used in conjunction with BMI and body fat percentage measurements to more accurately assess the health status of individuals.