In a natural wild environment, cats are hunters, spending many hours of the day looking for and capturing food. With many more unsuccessful hunting attempts than successful, hunting is a very time and energy consuming activity.
Living as part of a household, cats become accustomed to eating twice a day. They enjoy the comfort of you doing the hunting on their behalf. As a result, they experience less stimulation and activity normally associated with eating.
Additionally, a cat's digestive system is designed to take in multiple small meals throughout the day rather than two meals in twenty-four hours. Often cats learn to consume larger quantities in one or two sittings because they come to realise that food is not available at other times, but their natural instinct is to eat smaller amounts more often.
In many cases, owners misinterpret a cat's attempts to elicit social interaction, through vocalisation or rubbing, as a demand for food and when they realise that food treats can be elicited in this way they will quickly learn to develop this food soliciting behaviour. You can prevent this by increasing the frequency of feeding by spreading your cat's daily food intake between multiple small meals rather than two main sittings.
You can assist your obsessive eater by making feeding more fun and challenging event that is spread out over the day. At the same time, your pet will enjoy some exercise to help keep the waistline trim. Here are a few ideas for you to try:-
On another note, behavioural problems relating to food may not necessarily be a result of a food obsession. Any sudden or excessive weight loss or gain or a sudden increase or decrease in appetite should be discussed with a veterinarian.