Can waist-to-height ratio replace BMI? Why India is rethinking obesity checks

For decades, the Body Mass Index (BMI) has been the standard method used by doctors, hospitals and public health programmes to assess whether a person is underweight, overweight or obese. It is simple, quick and requires only two measurements height and weight. But as obesity-related illnesses continue to rise in India, many experts believe BMI alone is no longer enough to identify people who are truly at risk.

The Union Health Ministry has now recommended measuring the waist-to-height ratio (WHtR) in schools to identify children who may be at risk of obesity and cardiometabolic diseases such as diabetes, high blood pressure and heart disease. The recommendation reflects growing scientific evidence suggesting that fat stored around the abdomen is a better predictor of future health problems than body weight alone.

The move has generated discussion among doctors and public health experts. While many welcome the shift, they also point out that introducing waist measurements on a large scale, particularly in schools, will require proper training, standardised methods and sensitivity towards children's privacy and body image concerns.

WHY IS THE HEALTH MINISTRY CHANGING FOCUS?

India is witnessing a steady rise in obesity, especially among children and young adults. Along with this increase has come a surge in lifestyle diseases such as type 2 diabetes, hypertension, fatty liver disease and cardiovascular disease.

Experts say one reason these conditions are increasing is that many people who appear to have a "normal" body weight may still carry excess fat around their abdomen. This hidden fat often goes unnoticed when only BMI is used.

The Health Ministry believes measuring the waist-to-height ratio could help identify these individuals much earlier, allowing lifestyle changes and medical interventions before serious diseases develop.

WHAT IS BMI?

Body Mass Index is calculated by dividing a person's weight in kilograms by the square of their height in metres.

Based on the result, people are classified as:

• Underweight
• Normal weight
• Overweight
• Obese

BMI has remained the world's most commonly used obesity screening tool because it is inexpensive, easy to calculate and useful for large population studies.

However, experts say it has several important limitations.

WHY BMI IS NOT ALWAYS ENOUGH

The biggest criticism of BMI is that it does not distinguish between muscle and fat.

For example:

• An athlete with high muscle mass may have a high BMI despite having very little body fat.
• A person with a normal BMI may still have excessive abdominal fat and face a high risk of diabetes or heart disease.

BMI also cannot show where fat is stored in the body.

This matters because fat around the abdomen behaves very differently from fat stored elsewhere.

WHY BELLY FAT IS MORE DANGEROUS

The waist-to-height ratio focusses on central obesity, or fat stored around the waist.

Unlike fat under the skin, abdominal fat surrounds important organs such as the liver, pancreas and intestines. This fat is metabolically active and releases chemicals that contribute to:

• Insulin resistance
• Chronic inflammation
• High blood pressure
• High cholesterol
• Type 2 diabetes
• Heart disease
• Stroke

Because of this, experts say measuring waist size provides a better picture of a person's future health risks than body weight alone.

HOW IS WAIST-TO-HEIGHT RATIO CALCULATED?

The waist-to-height ratio is simple.

Formula:

• Waist circumference Height
• Both measurements should be taken in the same unit, such as centimetres.
• For most adults, experts recommend keeping the waist measurement less than half of the person's height.
• A waist-to-height ratio below 0.5 is generally considered healthy.

For example:

• Height: 170 cm
• Healthy waist: Less than 85 cm

This simple rule is easy to remember and does not require complicated calculations.

Most experts say not yet. BMI still has value because it is easy to measure, widely accepted and useful for tracking obesity trends across populations.

However, many believe the waist-to-height ratio should be used alongside BMI, rather than replacing it entirely. Using both measurements together can provide a more complete picture of an individual's health.

CHALLENGES IN SCHOOLS

Although measuring waist circumference only requires a measuring tape, experts say implementation will not be straightforward.

Some concerns include:

• Training school staff to take accurate waist measurements
• Following standard measurement techniques
• Ensuring privacy during screening
• Addressing body image concerns among adolescents
• Managing cultural sensitivities, particularly for girls

Without proper protocols, experts warn that inaccurate measurements or discomfort among students could reduce the effectiveness of the programme.

BEYOND THE MEASURING TAPE

Doctors emphasise that no single measurement can fully predict disease risk.

A person's overall health assessment should also include:

• Blood pressure
• Blood sugar levels
• Cholesterol profile
• Family history
• Physical activity
• Diet
• Smoking and alcohol use

These factors together provide a clearer understanding of cardiometabolic health than any one measurement alone.

As obesity and lifestyle diseases continue to place a growing burden on India's healthcare system, experts believe the focus must shift from simply measuring body weight to identifying the type of fat that poses the greatest health risk.

The Health Ministry's recommendation to use the waist-to-height ratio marks an important step towards more accurate screening and earlier detection of cardiometabolic diseases. While challenges remain, particularly in schools, experts say the approach has the potential to improve preventive healthcare if implemented with proper training, standardised protocols and public awareness.

Rather than replacing BMI overnight, the waist-to-height ratio may become an important addition to routine health screening—helping doctors identify high-risk individuals earlier and encouraging healthier lifestyles before disease develops.