A thought.. If you eat say 2000 calories in one sitting. You won't absorb 100 % of it right - some of it will pass through.
Also the body will use more energy handling it than eating closer to what you can absorb.
Aren't different calories easier or more energy demanding to absorb by the body?
Wouldn't those facts mean a calorie is not a calorie when it comes to digestion 
some people doesnt have enough brain to grasp the difference between real concepts and abstract ones like calories (and some do undersand but are just trolling).
In the real world, its impossible to eat calories alone. You eat a piece of matter that have lots of things in it, including calories.
Take for example salt. It has the propriety to make your organism retain water, thus gaining weight, and this effect is totally unrelated to the calorie aspect of it.