Obesity in pets is a frustrating, major health problem. Obesity in human children is similar. Prevailing theories accounting for the rising obesity rates – for example, poor nutrition and sedentary activity – are being challenged. Obesity interventions in both pets and children have produced modest short-term but poor long-term results. New strategies are needed. A novel theory posits that obesity in pets and children is due to ‘treats’ and excessive meal amounts given by the ‘pet–parent’ and child–parent to obtain affection from the pet/child, which enables ‘eating addiction’ in the pet/child and results in parental ‘co-dependence’. Pet–parents and child–parents may even become hostage to the treats/food to avoid the ire of the pet/child. Eating addiction in the pet/child also may be brought about by emotional factors such as stress, independent of parental co-dependence. An applicable treatment for child obesity has been trialled using classic addiction withdrawal/abstinence techniques, as well as behavioural addiction methods, with significant results. Both the child and the parent progress through withdrawal from specific ‘problem foods’, next from snacking (non-specific foods) and finally from excessive portions at meals (gradual reductions). This approach should adapt well for pets and pet–parents. Pet obesity is more ‘pure’ than child obesity, in that contributing factors and treatment points are essentially under the control of the pet–parent. Pet obesity might thus serve as an ideal test bed for the treatment and prevention of child obesity, with focus primarily on parental behaviours. Sharing information between the fields of pet and child obesity would be mutually beneficial.