Many people focus on their weight, but fewer understand what it actually says about their health. This is where Body Mass Index (BMI) becomes important. Body Mass Index (BMI) is a simple measure calculated from your height and weight measurements, and it helps indicate whether you are underweight, within a healthy range, overweight, or obese. It helps in assessing risk factors for certain health conditions. BMI is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²).
While BMI is a useful starting point, it does not tell the whole story. Your BMI results do not take into account your body composition. For example, you and your friend may have the same BMI, but your proportions of muscle and fat could be completely different. That is why BMI should never be used alone. To get a full picture of your health and wellness, it needs to be accompanied by other health indicators such as cholesterol levels, blood pressure, waist circumference, and blood sugar.
In fact, some individuals have a normal BMI but are not necessarily healthy. A person with high cholesterol, for example, may still fall into the healthy BMI range. This can be due to smoking, lack of exercise, a diet rich in saturated fats, or a family history of high cholesterol.[1] To truly understand your body composition — how much fat versus muscle you carry — you may consider consulting a healthcare professional or undergoing advanced scans like dual‑energy X‑ray absorptiometry (DEXA).
Knowing your BMI is important because it allows you to estimate your risk of obesity.[2] The World Health Organization defines obesity as a chronic, relapsing disease that arises from complex interactions between genetics, neurobiology (the state of your nervous system), eating behaviours, access to healthy food, market forces, and the broader environment.[3] Being overweight or obese puts you at greater risk of non‑communicable diseases (NCDs) such as Type 2 diabetes, high cholesterol, hypertension, heart disease, and stroke.
Interpreting your BMI results
For adults who are 20 years and older, those who fall into the underweight category have a BMI of less than 18.5. For an individual to be considered healthy, they need to have a BMI range of 18.5 to less than 25. An overweight person’s range is from 25 to less than 30. An obese person has a BMI of 30 or greater.
Obesity itself is further divided into three classes, ranging from moderate to severe, depending on the BMI value. Class 1 obesity covers BMIs from 30 to less than 35, class 2 obesity from 35 to less than 40, and class 3 obesity — also called severe obesity — is a BMI of 40 or higher.[4]
If you find yourself in the overweight or obese category, the good news is that there are practical steps you can take to manage your weight and improve your overall health. Consulting a healthcare provider is an important first step, as they can offer personalised advice based on your individual needs. Start by making changes that improve your overall health. Eat a balanced diet that meets your calorie and nutritional requirements, and aim for at least 150 minutes of moderate‑intensity exercise per week, such as brisk walking. These steps will support sustainable weight management and general well-being.
Knowing your BMI empowers you to take charge of your health at the most basic level. The lifestyle changes that are often recommended require discipline and remaining well-informed rather than expensive treatments. With just a calculator, a weighing scale, and a tape measure, you can monitor your progress and be well on your way to better health and wellness.
[1] https://www.cdc.gov/cholesterol/risk-factors/index.html
[2]https://www.hopkinsmedicine.org/all-childrens-hospital/services/healthy-weight-toolkit/assessments/bmi-assessment
[3] https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
[4] https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html