It is my opinion that are many causes and/or contributing factors to obesity, not one single. There are many well educated people who are championing only a single cause and declining others. Don at http://donmatesz.blogspot.com/2011/11/fatty-foods-and-sugar-addictive-like.html is one such person.
In my mind there is no doubt that addiction is one of the factors. There is also no doubt that insulin resistance is one of the factors that come into effect when we are overweight, and for sure when we are obese. Different cells become insulin resistant at different times and possibly by different methods. First the muscle cell, then fat cells and them liver cells. But that does not preclude the original drive to eat, aka, appetite to be stimulated by addiction,taste, cravings, add your own list. Once we become insulin resistant, ( full time, seasonally, occasionally) all the other things start, leptin signaling blocking, etc. Then there is hunger and cravings. Such is life.
Some of us obese, ex-obese need to address insulin resistance first, and our addiction, reward, craving causes later or vise - verse. For complete recovery we need to address all the causes. My list can be found on the page, Causes of Overeating.
Note added Nov 5: Others opposed to Dons view:
Videos worth watching found here
Lustig is good, the other less so but some good information.
Please be advised that this represents my current opinion, and my views have and will change. I am just trying to understand this complex issue and maintain recover from obesity. Maintenance of recovery is proving to be more difficult that actual weight loss. Much is separating theory and reality by n=1 testing.