What is a healthy BMI range for adults?
The WHO defines BMI categories as: Underweight < 18.5, Normal weight 18.5–24.9, Overweight 25–29.9, Obese Class I 30–34.9, Obese Class II 35–39.9, Obese Class III ≥ 40. A BMI of 18.5–24.9 is considered healthy for most adults of European descent. For Asian populations, health risks increase at lower thresholds — many guidelines use 23 as the overweight cutoff.
How is BMI calculated?
BMI = weight (kg) ÷ height² (m²). In imperial: BMI = (weight in pounds ÷ height in inches²) × 703. For example, a person weighing 70 kg at 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which is in the normal range.
Is BMI accurate for athletes and muscular people?
BMI cannot distinguish fat from muscle. A 100 kg bodybuilder at 1.80 m has a BMI of 30.9 (obese) despite very low body fat. BMI overestimates fatness in athletes and muscular individuals. For a more accurate picture, combine BMI with body fat percentage (measured by DEXA scan, Bod Pod, or Navy method) and waist circumference.
What does a BMI over 30 mean for health?
A BMI of 30+ is classified as obese and is associated with significantly elevated risks of type 2 diabetes, heart disease, sleep apnea, certain cancers, joint problems, and reduced life expectancy. However, BMI alone does not diagnose illness. Metabolically healthy obesity exists — always consult a doctor for a full health assessment.
What is a healthy BMI for children and teenagers?
BMI for children (ages 2–19) is interpreted using age- and sex-specific percentile charts, not the adult categories. A child's BMI is healthy if it falls between the 5th and 85th percentile for their age and sex. Above the 95th percentile is obese; below the 5th percentile is underweight. Adult BMI thresholds do not apply to children.
What is the BMI of an average person in the UK and US?
The average BMI in the UK is approximately 27.3 (overweight range). In the US it is approximately 29.9, just below the obese threshold. Over 70% of American adults and 64% of UK adults are classified as overweight or obese by BMI. This does not mean 70% are unhealthy — but it does highlight a significant population-level trend.