Is BMI really important?

What is BMI and why do we use it?

BMI is a measurement used to assess a person’s weight status in relation to their height. It is calculated by dividing an individual’s weight in kilograms by the square of their height in meters (BMI = weight (kg) / height (m)^2). While this calculation may seem complicated, BMI simply determines whether a person’s weight is appropriate for their height. The primary purpose of BMI is to quickly and easily categorize individuals into weight groups: underweight, normal weight, overweight, or obese.

BMI is widely used for the following purposes:

• To help shape public health policies for populations.
• To assist doctors, hospitals, and other healthcare providers in identifying potential health risks such as cardiovascular disease, type 2 diabetes, and certain cancers.
• To calculate an individual's energy expenditure and caloric needs to help with weight loss, maintenance, or weight gain.

Is it right for everyone?

While BMI is a convenient and useful tool for many, it may not accurately assess people with higher muscle mass, such as athletes and bodybuilders. Muscle is denser than fat, meaning it weighs more while taking up less space. If you’re an avid gym-goer and your BMI classifies you as "overweight," it may be due to your muscular physique rather than excess fat. Having more muscle can actually be beneficial for overall health and fitness, even if it raises your BMI.

Additionally, BMI may not accurately reflect health risks for older adults or individuals from different ethnic backgrounds, as body composition can vary even at the same BMI level. This highlights the challenge of applying a universal BMI scale to all populations. That said, research still supports BMI as a reliable starting point for most people looking to lose, gain, or maintain weight.

What else can be used?

Besides BMI, there are several other ways to measure body fat and assess overall health risks. These methods provide additional insights that BMI alone cannot, such as where fat is stored in the body.

Alternative weight assessment methods include:

• Waist-to-hip ratio, waist circumference, and waist-to-height ratio – These are simple, cost-effective ways to measure abdominal fat, which can indicate potential health risks. Excess weight around the abdomen is linked to higher levels of visceral fat—the type of fat that surrounds internal organs and is associated with increased inflammation, insulin resistance, and a higher risk of conditions like type 2 diabetes and heart disease. Recent research suggests that weight distribution may be just as important as total weight, making these measurements a valuable complement to BMI.
• Hydrostatic weighing – Also known as underwater weighing, this method is considered the "gold standard" for measuring body composition. It estimates body fat percentage with high accuracy but requires specialized equipment, making it inaccessible to most people.
• Skinfold caliper measurements – This method estimates body fat percentage by measuring skinfold thickness at different body sites. It is commonly used in sports nutrition but may be less accurate for individuals with higher body fat levels. Some people may also find it intrusive. Nonetheless, it is a practical way to track body fat over time.
• Body composition analysis (BIA or DEXA) – Techniques like Bioelectrical Impedance Analysis (BIA) and Dual-Energy X-ray Absorptiometry (DEXA) provide a detailed breakdown of muscle, fat, and bone mass. These methods offer a more comprehensive view of body composition but are costly and require specialized equipment, limiting their accessibility.