Final answer:
Obesity is defined by the body mass index (BMI), which is a measure of weight-to-height ratio. It can arise from various factors and can lead to severe medical conditions.
Step-by-step explanation:
Obesity is defined by the body mass index (BMI), which is a measure of an individual's weight-to-height ratio. The normal BMI range is between 18 and 24.9 kg/m². Overweight is defined as a BMI of 25 to 29.9 kg/m², and obesity is considered to be a BMI greater than 30 kg/m². Obesity can arise from factors such as overeating, poor diet, sedentary lifestyle, limited sleep, genetic factors, and diseases or drugs. Severe obesity or long-term obesity can lead to serious medical conditions such as coronary heart disease, type 2 diabetes, cancer, hypertension, and more.