BMI index – how to calculate it and interpret it correctly?

Body Mass Index (BMI) is calculated based on height and weight. It helps to approximate whether a person has a normal body weight. How should the results be interpreted?

BMI body mass index formula

How to calculate BMI? expressed in kilograms by the square of height expressed in meters. The method of calculation is always the same – regardless of age and gender – but in the case of children the indicator should be interpreted differently.

BMI = weight [kg] ÷ height2 [m].

Classification according to BMI value:

  • less than 18.5 – underweight
  • 18.5-24.9 – normal
  • 25.0-29.9 – overweight
  • 30 and over – obesity

Body mass index and health

Both a BMI that is too high and one that is too low can lead to a host of health problems, but it is the former that is far more common. The World Health Organization (WHO) has long classified obesity as a chronic disease of civilization. Worldwide, the number of people with a BMI above 25 exceeds 2 billion, and in Poland more than 60% of men and almost half of women are overweight or obese.

One of the most important factors responsible for weight gain is energy imbalance. In order to function, the body needs a certain amount of energy from food, obtained in the form of calories. Body weight usually remains the same when we consume a number of calories each day that is close to what we consume. However, if we eat more than we burn, we gain weight over time. Proper weight also depends on genetics, as well as the amount of exercise. To achieve it, you need to be active and follow certain eating habits. The most important of these is to eat 5 reasonably sized meals a day and choose products carefully – to make sure your diet is rich in wholesome, low-processed foods. Sometimes it is also worthwhile to get nutritional counseling. A nutritionist will suggest what to eat and in what quantity to lose weight. Dietary supplements can also help maintain health.

Although the BMI index is useful in screening for weight problems, it has its limitations. It can be unreliable for athletes and people with very muscular physiques, and in the elderly. New research also indicates that it is not the BMI value itself, but the percentage of body fat that is a better measure of health.