Measuring BMI is the generally accepted first step to determine the degree of overweight. The BMI is easy to measure, reliable, and correlated with percentage of body fat and body fat mass. BMI provides a better estimate of total body fat compared with body weight alone.
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BMI
- Underweight – <18.5 kg/m2
- Normal weight – ≥18.5 to 24.9 kg/m2
- Overweight – ≥25.0 to 29.9 kg/m2
- Obesity – ≥30 kg/m2
- Class I – 30.0 to 34.9 kg/m2
- Class II – 35.0 to 39.9 kg/m2
- Class III – ≥40 kg/m2 (also referred to as severe, extreme, or massive obesity)
*BMI may overestimate the degree of adiposity in individuals who are overweight but very muscular (for example, professional athletes or bodybuilders) and underestimate it in older persons due to loss of muscle mass associated with aging.