The key to not gaining weight over Christmas is portion control. We all need to be careful about how much we are putting onto our plates and the extra amount of nibbles we are eating.
Bear in mind that a female and male require approximately 1500 and 2000 calories respectively for weight loss and 2000 and 2500 calories respectively for weight management. One extra mince pie can contain up to 200 calories so if you have more than one or two a day that can be a large portion of your calorie intake. If you do want an extra mince pie and would like to maintain or lose weight over Christmas try reducing portion size in other areas.
Ways you can achieve portion control include using a smaller plate a meal times, reducing your snacking between meals, consuming low fat foods (less than 5% per 100 grams) and counting the number of calories you are consuming. All these will help in allowing you enjoy Christmas and its extra variety of foods and hopefully still allow you to maintain your weight.