One of the hardest times of year to diet is during the winter months. Our bodies are triggered to gain weight for the long cold months ahead much like wild animals. That is one major reason why there are so many old traditions for feasting in the late Autumn and early winter. In order to break that cycle you must first be aware of it. Know that your body is trying to gain weight in anticipation of a winter with lack of food.
Break the cycle by going outside daily and doing some mild exercise, even if it just for a walk. Keep it up through the winter. Your body will then have a less of a tendency to want to eat.