What is a healthy BMI range?
WHO defines: Underweight < 18.5, Normal 18.5–24.9, Overweight 25–29.9, Obese Class I 30–34.9, Class II 35–39.9, Class III ≥ 40. For Asian populations, the WHO recommends lower thresholds (overweight ≥ 23, obese ≥ 27.5).
Is BMI accurate for athletes and bodybuilders?No. BMI measures weight-for-height but cannot distinguish muscle from fat. A 200-lb bodybuilder at 5'10" has BMI 28.7 (overweight) yet 8% body fat. For athletic bodies, DEXA scan, hydrostatic weighing, or Navy body fat
formula are more accurate.
How do I calculate BMI manually?
Formula: BMI = weight (kg) ÷ height² (m²). Example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 = 22.86. Imperial: BMI = 703 × weight (lbs) ÷ height² (inches²).
Does BMI change with age?
The formula is the same across ages, but interpretation differs. For children (2–19), BMI is plotted on CDC/WHO growth charts as a percentile. For elderly adults (65+), a BMI of 25–29.9 may be associated with lower mortality risk than for younger adults (the 'obesity paradox').
What is morbidly obese BMI?
Morbid obesity (Class III) is BMI ≥ 40, or BMI ≥ 35 with a serious weight-related health condition (type 2 diabetes, hypertension, sleep apnea). This classification is used for bariatric surgery eligibility criteria.
How much weight do I need to lose to lower my BMI by 1 point?
BMI drops by 1 point when weight decreases by height² kg. For a 175 cm (1.75 m) person: height² = 3.06 m², so a 1-BMI-unit drop requires losing ~3.1 kg (6.8 lbs).