BMI Explained: What It Means & Its Limitations

Body Mass Index (BMI) is the most widely used screening tool for weight categories. Understanding it — including its limitations — helps you interpret your result in the right context.

The BMI Formula

BMI is calculated as:

BMI = weight (kg) / height (m)²

Or in imperial units:

BMI = (weight in lbs × 703) / height (inches)²

BMI Categories (WHO Standard)

BMI Range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 and above	Obese

BMI for Asian Populations

Studies show that Asian populations (including Indians) have higher body fat percentage at the same BMI compared to Western populations. Many health organisations recommend adjusted cut-offs for South Asians:

• Overweight: BMI ≥ 23
• Obese: BMI ≥ 27.5

What BMI Does Not Tell You

BMI has significant limitations and should not be used as a sole indicator of health:

• Does not distinguish muscle from fat — a muscular athlete may have a "overweight" BMI despite having low body fat.
• Does not indicate fat distribution — abdominal fat (visceral fat) is a stronger predictor of cardiovascular risk than total fat.
• Not accurate for elderly individuals — older adults tend to lose muscle mass, so BMI may underestimate health risks.
• Ignores bone density — people with high bone density may score in the overweight range despite being healthy.

Better Metrics to Use Alongside BMI

• Waist circumference: Risk increases above 80 cm (women) or 90 cm (men) for South Asians.
• Waist-to-hip ratio: Above 0.85 (women) or 0.90 (men) indicates increased abdominal obesity risk.
• Body fat percentage: Measured via DEXA scan, BIA, or skinfold calipers — more accurate than BMI.

When to Seek Medical Advice

If your BMI is below 18 or above 30, consult a doctor for a comprehensive health assessment. BMI is a screening tool, not a diagnosis. Your doctor will consider blood work, blood pressure, and lifestyle factors alongside BMI.

Calculate your BMI instantly with our BMI Calculator.