Obesity has traditionally been identified using Body Mass Index (BMI), a measurement calculated using a person's height and weight. For years, doctors have relied on this method to assess whether someone falls within a healthy weight range or may have obesity. However, experts now believe that BMI alone may not always provide a complete picture of a person's health.

Why? Because body weight does not necessarily reflect how much fat a person carries or where that fat is stored.

For instance, someone may have a BMI within the normal range but still have excess fat around the abdomen and internal organs. Similarly, people with greater muscle mass may have a higher BMI without having excessive body fat. This makes it difficult to accurately assess obesity using height and weight alone.

To address these limitations, researchers are exploring a more comprehensive approach that considers body composition, waist circumference and the impact of excess body fat on overall health.

New Obesity Assessment Goes Beyond Height and Weight

The newer approach focuses on more than just a person's weight and height. It also considers waist circumference, excess body fat and whether fat accumulation is affecting normal bodily functions.

Research suggests that combining these measurements may help identify health risks more effectively than relying on BMI alone.

This does not mean BMI has become irrelevant. Instead, it highlights the importance of looking at body composition and the distribution of fat to understand a person's health more accurately.

The approach may also help identify individuals who appear healthy based on their BMI but could have underlying metabolic health concerns.

How Is Obesity Traditionally Measured Using BMI?

Before understanding the newer approach, it is important to know how BMI works.

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

The commonly used BMI categories for adults are:

• Below 18.5: Underweight

• 18.5–24.9: Normal weight range

• 25–29.9: Overweight

• 30 or above: Obesity

However, BMI has certain limitations. It does not distinguish between muscle mass and body fat, nor does it indicate where fat is distributed in the body.

This is why researchers increasingly emphasise the importance of understanding body composition and fat distribution.

Excess fat around the abdomen and internal organs, in particular, is associated with a higher risk of conditions such as heart disease, Type 2 diabetes and other metabolic disorders.

The research analysed health information from more than 800,000 people to examine how different methods of identifying obesity could help predict health outcomes.

What Does the New Research Reveal?

Researchers examined an approach known as CAD-Obesity, or Combined Anthropometric Definition of Obesity. Unlike conventional BMI measurements, this method also considers waist circumference and excess body fat.

The study reviewed medical records from four large population groups in China, Spain, the United Kingdom and the United States. Data from three of these groups included records of more than 50,000 deaths.

Using nearly 15 years of health data, researchers compared the ability of BMI and the newer assessment method to identify obesity-related health risks.

The findings indicated that BMI-based assessments may overlook certain individuals who have excess body fat despite having a BMI within the normal range. A more comprehensive assessment could help identify these cases more effectively.

Two Categories of Obesity Explained

The newer understanding of obesity also distinguishes between two important conditions:

1. Clinical Obesity

Clinical obesity refers to a condition in which excess body fat begins to affect the normal functioning of organs and the body's overall health.

It may be associated with health complications such as heart failure, sleep apnoea and other medical conditions. In such cases, obesity is not simply a measurement concern but a condition that is already affecting bodily functions.

2. Preclinical Obesity

Preclinical obesity refers to a condition in which excess body fat is present, but the normal functioning of organs has not yet been significantly affected.

However, individuals may still have an increased risk of developing obesity-related health conditions in the future. Regular health assessments and appropriate medical guidance can help monitor these risks.

Why Is This New Approach Important?

A more comprehensive understanding of obesity could improve how doctors identify and manage health risks. Here are some important benefits:

1. Identifying Hidden Obesity

Some individuals may have a BMI within the normal range but still carry excess fat around their abdomen. Looking at waist circumference and body composition can help identify such cases that BMI alone might miss.

2. Distinguishing Between Muscle Mass and Body Fat

People who participate in strength training and other physical activities may develop greater muscle mass. Since muscle contributes to overall body weight, their BMI may be higher without necessarily indicating excess body fat.

Considering body composition can therefore provide a more meaningful assessment.

3. Better Assessment of Heart Disease and Diabetes Risks

Excess abdominal fat is associated with an increased risk of cardiovascular diseases, Type 2 diabetes and metabolic disorders.

By considering additional measurements alongside BMI, healthcare professionals may be able to assess these risks more effectively and recommend appropriate medical care.

4. More Individualised Treatment

Obesity does not affect everyone in the same way. Some individuals may have excess body fat without noticeable health complications, while others may already experience problems involving the heart, metabolism or other organs.

A comprehensive assessment can help doctors understand an individual's health condition and develop a treatment plan according to their medical needs.

The Bottom Line

The understanding of obesity is evolving beyond traditional height-and-weight measurements. Although BMI remains a useful screening tool, it cannot independently explain body composition, fat distribution or the impact of excess body fat on overall health.

The newer approach places greater emphasis on these factors, helping healthcare professionals develop a more complete understanding of obesity and its associated health risks.

The key takeaway is that health cannot be understood through a single number. A comprehensive medical assessment, early identification of health concerns and appropriate professional guidance are essential for better long-term health.