Christmas dinner itself isn’t a particularly calorie dense, it is after all mainly vegetables and lean meat. Poor portion control can mean you eat more than you need, but the amount you over eat by won’t generally be drastic.
The big impact here is from the extras, in particular the calorie dense ones. Chocolates, mince pies, salted nuts, crisps, sausages wrapped in bacon, cheese etc
You get the idea.
This for most people where the damage is done, especially as these things tend to be not confined to a single day but spread across many, many days.
Keep these in check by having them out for fewer days, having lower calorie density options available (lean meats, vegetables, fruit, soups etc) and you will see a big difference.
Alcohol in control
Alcohol in the build up to Christmas, through Christmas day and onto New Years is a big dose of additional energy your body has to deal with. But more importantly a lot of loose decision making when it comes to food choices and capacity.
Boozy beverages primarily consist of water, pure alcohol (chemically known as ethanol), and variable amounts of sugars (i.e., carbohydrates); their content of other nutrients (e.g., proteins, vitamins, or minerals) is usually negligible. This is because they don’t really contain any nutrients.
Any calories provided by alcoholic beverages are derived from the carbohydrates and alcohol they contain.
The carbohydrate content varies greatly among beverage types. For example, whiskey, cognac, and vodka contain no sugars; red and dry white wines contain 2 to 10 grams of sugar per litre (g/L); beer and dry sherry contain 30 g/L; and sweetened white and port wines contain as much as 120 g/L. Similarly, the alcohol content varies greatly among beverages, ranging from approximately 40 to 50 g/L in beer and coolers, to approximately 120 g/L in wine and pre-packed cocktails, to 400 to 500 g/L in distilled spirits. An average drink—namely, 5 ounces (oz) of wine, 12 oz of beer, or 1.5 oz of distilled beverage—contains 12 to 14 grams of alcohol. Pure alcohol provides approximately 7.1 kilocalories per gram (kcal/g), compared with 4 kcal/g for carbohydrates. Thus, a 12–oz can of beer contains approximately 100 calories.
So yes, there are calories in Alcohol and yes this won’t help.
But your ability to make good decisions when intoxicated is pretty poor (I know you ????) .
To overcome these alcohol related problems you could drink less or hide the high calorie snacks from your drunken self.
Burn more
I’m not saying you have to go to the gym, there are plenty of other days you can do that the rest of the year. But keeping active and moving over Christmas will help you burn some extra calories and separate you from the snacks, just don’t pack provisions.