system
Given the following post, respond as if you're commenting on Reddit:
human
I think weight loss is more complex than calories in, calories out. CMV

I think it comes down to the kind of food you eat and how much of it you eat.

Sam Feltham ate over 5,000 calories per day for 21 days. His diet consisted of eggs, fish, meat, nuts and green vegetables. After calculating his BMR he estimated he'd put on 13 pounds by the calories in/calories out, but only put on 2.8 at the end of 21 days. His daily exercise routine did not change. Why did he not gain 13 pounds? Why did he only gain 2.8 if calories in/calories out is how simple weight loss is?

Mark Haub lived on a diet of basically only junk food for two months and lost 27 pounds. Twinkies, Doritos, hostess cakes, etc. However, he restricted his diet to only 1,800 calories per day. If he would have eaten 5,000+ calories per day of food like this, do you think he would have still lost 27 pounds?

I think calories in/calories out oversimplifies it. Eating natural foods like Sam Feltham did don't cause as much weight gain as junk food.
gpt
One thing you need to understand about "calories" is that (human) nutrition actually uses fairly inaccurate figures, from a real-world-effects standpoint.  The number that you see in the nutrition label is determined by how much energy can be taken out by completely burning it in a furnace.  As an extreme example of how this can be a bad measurement, sugar and sawdust would show (approximately) the same calories by that test, despite sawdust being completely indigestible.

Whole and uncooked foods fare better in that system, as people can not digest them as fully or as easily.

Calories in/out works, as long as you account for the losses due to some being indigestible and the metabolic costs of digesting the food.