1. Due to the thermic effect of food it will take anywhere from 10-25% of those calories just to digest the carbs and proteins. So the meal sits at roughly 1,700.
2. Are you in a fasted state? Depleted glycogen? Will determine if the carbs go toward refilling liver/muscle glycogen as opposed to fat stores.
3. Is there fiber in this 2,000 calories? Fiber is indigestible but technically contains calories, however they can usually be subtracted. In the case of say; fiber from seeds etc. , it contains actual oils so it should be considered..Where as psyllium husk is almost purely fiber.
4. How big are you? How much lean mass do you carry? How much are you eating in addition to this meal throughout the day?
5. If the meal contains a high ammount of a protein source like steak, it will take hours to fully break down into usable amino acids, thus blunting the impact on fat stores. The fats have to be broken down in the liver before use, also slowing them down.
The list could go on depending on more details.
If you are already eating a maintenance diet and add 2,000 calories of white rice in 1 sitting, it is safe to say whatever your body doesn't use for energy within 2 hours which is probably 500 calories or so will be stored as a combination of glycogen and fat.
Roughly* 3,500 calories is 1lb of fat so 2,000-500=1,500-100(glycogen)=1,400 calories (roughly .4 lb of fat gain)