What is the Body Mass Index (BMI)?

1 November 2024 –

Ernesto Escobar, MD

The Body Mass Index (BMI) is the ratio between our weight and body surface area, expressed in kilograms per square meter (kg/m²). It is the easiest indicator to determine if a person is within the normal weight range for their height.
This measurement helps classify, on an initial level, the degree of overweight, obesity, or malnutrition a person may have. However, today, there are other measurements that nutrition specialists use to determine body composition, such as body fat percentage, visceral fat, muscle mass, etc.
When the Body Mass Index (BMI) is 25, the patient is classified as overweight. When it is:
  • 30, it corresponds to Class I Obesity
  • 35, it corresponds to severe obesity
  • 40 or higher, it corresponds to Morbid Obesity.
Based on the information above, the indication for Bariatric Surgery begins at a BMI of 35 kg/m². However, a patient with a BMI of 30 who has obesity-related conditions may also benefit from surgery (especially if they have Type 2 Diabetes) to control or fully reverse these conditions (Metabolic Surgery).
Bariatric and metabolic surgery helps patients lose weight to achieve a healthy state, improve their quality of life, and also control, combat, and prevent obesity-related diseases.

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