The World Health Organization (WHO) defines overweight and obesity as the abnormal or excessive accumulation of body fat that can pose a risk to health. Obesity is a condition in which a person has accumulated an unhealthy amount of body fat, usually resulting from an imbalance between calorie intake and expenditure. Consuming a high number of calorie-dense foods without a corresponding increase in physical activity can cause weight gain, while reduced physical activity can also contribute to an energy imbalance and lead to weight gain.

The body mass index (BMI) is a common and simple measure used to classify overweight and obesity in adults. It is calculated by dividing a person’s weight in kilograms by the square of their height in meters (kg/m2). According to the World Health Organization (WHO), a BMI of 25 or greater is considered overweight, while a BMI of 30 or greater is considered obese.