Obesity affects an estimated 25-40% of companion dogs and cats in developed countries, representing the most prevalent nutritional welfare problem in pet medicine. Excess body weight causes joint pain (osteoarthritis), reduced exercise tolerance, respiratory compromise, metabolic disease (diabetes in cats), and shortened lifespan. Owner perception is a major barrier: surveys indicate 50-70% of owners of overweight pets believe their pet is normal weight. Veterinary weight assessment using body condition score (BCS 1-9 scale) provides an objective tool, but communication of results requires sensitivity to avoid owner defensiveness. Weight management programmes combining caloric restriction with structured exercise show 1-2% bodyweight loss per week as optimal. Prescription weight management diets outperform generic restriction. Prevention through life-stage appropriate feeding and regular BCS monitoring is more effective than treatment. Veterinary welfare guidelines now include obesity as a chronic welfare condition requiring active management.