BMI and waist size still matter—but health is more than a number

Body mass index (BMI) and waist circumference remain key tools for assessing a healthy weight range. These measurements, alongside other tests, help doctors evaluate potential health risks. Yet, experts stress that no single number should define overall health.

For over two decades, international guidelines—led by the World Health Organization—have kept standard BMI categories largely unchanged. Adults with a score below 18.5 are classified as underweight, while 25 or above indicates overweight, and 30 or higher signals obesity. Recent updates now suggest combining BMI with additional metrics for greater accuracy. The traditional BMI scale was established in 1998 and has seen few major revisions since. However, refinements now include age-adjusted ranges, such as a higher optimal BMI for those over 65. Guidelines also increasingly recommend supplementary measures, like waist circumference or body fat percentage, to address limitations in BMI alone.

Ethnic differences and body composition variations can affect how accurately BMI reflects health risks. For example, a 2025 proposal in The Lancet suggests confirming obesity in individuals with a BMI of 30 or above by also checking waist size or fat metrics. This approach helps identify clinical obesity—particularly in cases where comorbidities are present—in around 80% of high-BMI patients.

Where body fat is stored also plays a role in health risks. Excess weight around the waist poses greater concerns than fat distributed elsewhere. Because of this, doctors often consider waist-to-hip ratio alongside BMI for a clearer picture.

For those looking to maintain a healthy weight, lifestyle adjustments are key. Recommendations include eating nutrient-rich foods, exercising regularly, getting enough sleep, and managing stress. People advised to gain weight might focus on protein-rich snacks, whole foods, and protein shakes between meals. In some cases, doctors may refer patients to specialists, such as dietitians or physical therapists, for personalised support.

While stepping on a scale can feel uncomfortable for some, doctors emphasise that weight is just one part of a broader health assessment. Factors like muscle mass, bone density, and individual risk profiles all contribute to determining a healthy range. BMI and waist measurements continue to serve as useful starting points for evaluating weight-related health risks. However, doctors now combine these figures with other tests and personal health factors for a more complete assessment. The goal remains tailored advice—whether for weight maintenance, loss, or gain—to support long-term well-being.