BMI is a key measure for overweight (25-29.9 kg/m²) and obesity (≥30 kg/m²), with higher risks of diseases like diabetes and CVD. Ethnic differences in BMI-related risks exist, with Asians at higher risk at lower BMIs. Obesity prevalence is higher in non-Hispanic blacks and Hispanics. Overweight and obesity increase morbidity, mortality, and healthcare costs. Treatment includes lifestyle changes, medication, and surgery, with bariatric surgery being the most effective.