Understanding your relationship to food and triggers for over eating are also important. If you are eating healthy food but are still over-consuming then yes you will put weight back on.
But diet would rank about 70% of the equation for weightloss in my books since you can workout but then easily put back on the calories that you just took off if you are not being smart.
I totally agree. Over eating is a huge part and is a trained process. Rather than your stomach asking for food when it is empty it is asking when it isn't full.