There are several untenable positions on the origins of obesity. While personality has a definite biologic origin, it is a later evolutionary acquisition. Emotion and consciousness are the last layers of our development in the formation of who and what we are. Weight and weight control are much more fundamental mechanisms. The metabolism of energy, and therefore weight, is the most basic life function, mandated for us to adapt to our environment and secure our evolutionary status.
Every human is a unique individual.
Who we are is determined by a complex interrelationship of genetics and environment. Genetics seems to be winning out. Some humans have always been heavier than others. Whether this is a normal adaptive mechanism, or a pathologic exaggeration of a normal mechanism is not known. Regardless, weight and its control are much more than either self-will or emotion can explain or direct.