Obesity means having excess body fat and increases the risk of diseases like diabetes and heart disease. It occurs when calorie intake exceeds calories burned due to factors like genetics, diet of high-fat foods, and physical inactivity. Maintaining a healthy diet with more fruits and vegetables while being physically active can help prevent weight gain and related diseases. Reasons why obesity continues to be a problem include changes to diets with more processed foods and less home cooking, increasing sedentary lifestyles with less physical activity, and ineffective yo-yo dieting instead of sustainable lifestyle changes with healthy eating and exercise habits long-term.