Doting owners are often blamed when pets put on a few pounds.
But experts say that in many cases obese dogs and cats are 'emotional eaters'.
They also consume more than they need simply to cope with boredom or stress, research has found.
That means, if they have gained weight, it could be because they have been through a traumatic or emotional event.
New claims have also suggested that putting an overweight cat or dog on a diet could make them unhappy, because the owner is taking away their 'coping mechanism'.
The study claims the obesity rate is as much as 25 per cent in cats, and 45 per cent in dogs.
The problem has been likened to that of Bridget Jones, the singleton who hides away from her troubled love life by eating, with vets believing some pets use food to cope with sadness, according to The Sunday Telegraph.
Comfort eating in humans tends to involve high calorie foods which the individual chooses, including ice cream, and chocolate.
But research shows animals are less fussy, and will go on a comfort binge even if the only food on offer is their usual dog or cat food.
The claims are made in research contained in the latest edition of the Journal of Veterinary Behavior by Dr Franklin McMillan, a vet and former clinical professor of medicine at the Western University of Health Sciences College of Veterinary Medicine, in California.
He said 'emotional eating' in pets, could be triggered by feelings including boredom, anxiety and depression.
But the research has also suggested overeating could also be a sign of pleasurable emotional state, as well as a psychological state of turmoil.