Is a calorie just a calorie?

If you eat 2000 calories of bread compared to 2000 calories of red meat, no you are not getting the same thing. Yes that calorie intake will be the same, but that bread will be turned into quick energy resource, while the red meat will help with oxygen uptake. So completely different. That is not all that carbs and protein are used for but that is just an example. Hope that answered your question.