From the Guidelines
A Body Mass Index (BMI) of 30 or higher is classified as obese, with classes ranging from Class 1 (BMI 30-34.9) to Class 3 (BMI 40 or higher), as defined by the most recent and highest quality study 1.
Definition of Obesity
Obesity is a major health concern, and BMI is a widely used screening tool to assess health risks associated with excess weight.
- BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters.
- The classification system helps healthcare providers assess health risks associated with excess weight, including heart disease, type 2 diabetes, and certain cancers.
Limitations of BMI
However, BMI has limitations, as it does not distinguish between fat and muscle mass or account for fat distribution.
- Some individuals, particularly athletes with high muscle mass, may have a high BMI without excess fat.
- For a complete health assessment, BMI should be considered alongside other factors like waist circumference, blood pressure, blood sugar levels, and overall lifestyle habits.
Classification of Obesity
The classification of obesity is based on BMI, with the following categories:
- Class 1: BMI 30-34.9
- Class 2: BMI 35-39.9
- Class 3: BMI 40 or higher This classification system is supported by the most recent study 1, which provides the most up-to-date and high-quality evidence on the definition and classification of obesity.
From the Research
Definition of Obesity
The Body Mass Index (BMI) range for obesity is defined as a BMI of 30 kg/m2 or higher 2, 3, 4.
BMI Categories
The World Health Organization defines the following BMI categories:
- Underweight: BMI < 18.5 kg/m2
- Normal weight: BMI = 18.5-24.9 kg/m2
- Overweight: BMI = 25-29.9 kg/m2
- Obesity: BMI ≥ 30 kg/m2 Obesity can be further subdivided into:
- Grade 1 obesity: BMI = 30-34.9 kg/m2
- Grade 2 obesity: BMI = 35-39.9 kg/m2
- Grade 3 obesity: BMI ≥ 40 kg/m2 3
Key Points
- A BMI of 30 kg/m2 or higher is considered obese 2, 3, 4
- Obesity is a major risk factor for various chronic diseases and poor physical functioning 4
- Behavioral lifestyle interventions can result in clinically significant weight loss in obese individuals 5
- Comprehensive and intensive behavioral interventions, including multiple components such as diet, physical activity, and behavioral strategies, can be effective in achieving weight loss 5