Body Mass Index

The body mass index (BMI) is a measure used to assess a person's body mass based on their height and weight. The BMI is calculated by dividing the body weight in kilograms by the square of the height in meters. The resulting figure gives a rough estimate of whether a person is underweight, normal weight, overweight or obese.

The formula for calculating the BMI is:

BMI=Weight in kg(Height in m)2BMI=(Height in m)2Weight in kg

For example, a person who weighs 70 kg and is 1.75 m tall would have a BMI of about 22.9, which is within the range for normal weight

The World Health Organization (WHO) classifies BMI into the following categories:

• Under 18.5: Underweight
• 18.5 - 24.9: Normal weight
• 25 - 29.9: overweight
• 30 and over: Obesity (adiposity)

• Health assessment: BMI is often used as a simple and quick indicator for assessing health status. A BMI that is too high or too low can indicate potential health risks.
• Limitations: BMI does not take into account the distribution of muscle and fat mass in the body. Therefore, it can lead to misleading conclusions for very muscular individuals or those with a high bone structure.
• Not a sole indicator of health: While BMI can provide useful information, it should not be used as the sole indicator of health or fitness.

• Medical assessment: Physicians often use BMI as one of several tools to assess a patient's overall health.
• Public health: BMI is used in public health research to analyze patterns of overweight and obesity in the population.
• Personal health monitoring: Individuals can use BMI to keep track of their own body mass and make lifestyle changes if necessary.

• Factors not taken into account: BMI does not directly measure body fat and does not take into account factors such as muscle mass, bone structure and general body composition.
• One size fits all: BMI offers a standardized approach that does not take into account individual differences in physique and health.

Can the BMI be used for children?

Yes, but special BMI tables are used for children and adolescents that take age and gender into account.

Is it possible to have a healthy BMI and still be unhealthy?

Yes, people with a "normal" BMI may still have unhealthy levels of body fat or have other health problems. Therefore, BMI should not be considered in isolation.

How accurate is the BMI in older adults?

In older adults, the BMI can be less meaningful, as physique and body composition can change with age. For example, the loss of muscle mass with age can mean that the BMI remains normal even though the body fat percentage has increased. It is therefore important to also consider other health indicators such as general fitness and mobility.

How should BMI be used in conjunction with other health indicators?

BMI should be used as one of several health indicators. Other important factors include blood pressure, cholesterol levels, blood sugar levels and physical fitness. A comprehensive health assessment should always include a combination of these factors to get a complete picture of a person's health.

Are there situations in which the BMI should not be used?

The BMI may not be suitable for people with exceptionally high muscle mass, such as bodybuilders or competitive athletes, as their high muscle mass can lead to a high BMI that is misinterpreted as overweight. Similarly, the BMI is not applicable to pregnant and breastfeeding women as it does not take into account the changing physical conditions during and after pregnancy.