Background: This study investigated whether the body condition score (BCS) and/or culture influences the quality of life (QoL) of dogs, as evaluated by the owner, and whether the BCS is influenced by feeding and exercise and its owner’s culture. To this end, a questionnaire was administered to 355 selected dog owners (Thai and Dutch). Their dogs had a BCS of 3 (normal weight), 4 (overweight) or 5 (obese) but no other physical problems. Instead of using Likert scales, continuous scales were used. Further, data for the questionnaire items were transformed using an integrated z-score methodology. Results: The magnitude of factor loadings was similar to that reported in a previous study, indicating that the questionnaire is not culture specific. QoL scores for general sickness were significantly higher (worse) in dogs with a higher BCS. Thus even though the dogs were apparently healthy, the BCS influenced the perceived QoL of the dog. Immobility was seen more often in dogs with a higher (poorer) BCS than in dogs with a lower (better) BCS; however, there was no clear relationship between immobility and total activity. The higher the BCS, the less owners felt in control of feeding and exercise. The BCS was higher in the dogs of owners who did not like to exercise. The Thai dogs showed more separation-related behaviour problems when their owner left home than did the Dutch dogs. Conclusions: The QoL of overweight and obese dogs is mainly influenced by the dog’s physical status. The owners of dogs with a high BCS have less perceived control over feeding and exercise. Our findings indicate that owner attitudes and beliefs essentially cause obesity as a result of a lack of knowledge and perceived control.