Body Mass Index (BMI) is the most widely used tool globally for classifying weight and estimating associated health risks. With rising obesity rates in the Arab world and globally, understanding this index accurately has become a health necessity, not a luxury.
Body Mass Index was measured by Belgian physician Adolphe Quetelet in the 19th century but became widely used medically in the 1970s. The formula is simple: BMI = Weight (kg) ÷ [Height (m)]².
Example: a person weighing 80 kg and 1.75 m tall. BMI = 80 ÷ (1.75 × 1.75) = 80 ÷ 3.0625 = 26.1. This falls in the "overweight" category according to WHO charts.
In some systems, weight in pounds and height in inches are used: BMI = (Weight in lbs ÷ [Height in inches]²) × 703. The calculator handles this automatically regardless of the units used.
WHO classification: below 18.5 = Underweight. 18.5 to 24.9 = Normal (healthy) weight. 25 to 29.9 = Overweight (pre-obesity). 30 to 34.9 = Class I obesity. 35 to 39.9 = Class II obesity. 40 and above = Class III (morbid) obesity.
Some Asian studies — including those relevant to Arab populations — suggest slightly lower thresholds: normal ends at 23 (instead of 24.9), overweight is 23 to 27.5, and obesity starts at 27.5. The reason is that cardiovascular disease and diabetes risks appear at lower BMI values in people of certain body compositions.
For children and adolescents (ages 2–18), the adult charts do not apply — a percentile chart based on age and sex is used.
BMI does not distinguish between fat and muscle: a professional athlete with significant muscle mass may show a BMI of 28 (overweight) despite being in peak health. Conversely, a slim person with high visceral fat (around organs) may show a BMI of 22 but carry significant health risks.
Belly fat is more dangerous than thigh fat: the distribution of fat matters more than its total. Abdominal and visceral fat is more strongly linked to heart disease and diabetes than fat in the hips and thighs. Waist circumference is a necessary complement: risk rises above 102 cm for men and 88 cm for women.
Complementary factors for assessing healthy weight: body fat percentage (measured by specialized equipment or formulas), waist circumference, waist-to-hip ratio, and your physical activity level, age, and health history.
Obesity rates have risen sharply worldwide; the WHO reports that more than one billion people live with obesity globally. Multiple intertwined causes: physical inactivity, diets high in sugar and saturated fat, and psychological stress.
Obesity-related diseases: type 2 diabetes, cardiovascular disease, hypertension, and sleep apnea. Preventing these conditions begins with maintaining a healthy weight.
Practical prevention steps: 30 minutes of moderate daily physical activity (brisk walking, swimming, cycling), reducing sugar, soft drinks, and fast food, and maintaining adequate and regular sleep.
If your BMI is below 18.5: there may be a nutritional deficiency or underlying health problem that warrants medical assessment. Do not overlook underweight any more than overweight.
If your BMI is above 30: a full medical evaluation is advised, including blood tests (blood sugar, cholesterol, kidney and liver function). Managing weight in collaboration with a doctor or dietitian is better than any random diet.
Before starting any intensive weight-loss program or strenuous exercise, consult a doctor — especially if you are over 40 or have a medical history.
A: The ideal range according to WHO standards is 18.5 to 24.9. However, the optimal target varies by age, sex, ethnicity, and muscle mass. Consult your doctor to determine the ideal weight appropriate for you personally.
A: The basic WHO charts do not differentiate by sex, but research shows women naturally carry a higher percentage of body fat than men at the same BMI value. Some doctors take this into account when interpreting results.
A: No. For children and adolescents (2–18 years), a percentile chart by age and sex is used, because body composition changes with growth. Raw BMI is not a reliable standalone measure for children.
A: Several studies have shown that some people gain weight during Ramadan due to sugar- and fat-rich meals at night and reduced movement. However, with a healthy Ramadan regimen, weight gain can be avoided and weight can actually be lost.
A: The correlation is strong. A BMI above 30 significantly raises the risk of type 2 diabetes. However, visceral fat (around the belly) is more closely linked to diabetes than subcutaneous fat. Many diabetes patients have a BMI between 25–30, not necessarily above 30.
A: Not necessarily. It is possible to have a normal BMI alongside high visceral fat ("skinny fat"). Good health encompasses regular physical activity, a balanced diet, routine check-ups, and adequate sleep — not just a number on a scale.