"same amount of calories"

I think this is too big of an assumption. Ultra processed foods are generally less filling and easier to digest. Eating 1000 calories of cereal or potato chips is easy. Eating 5 chicken breasts at once borderline impossible for most people. Whole foods tend to make is harder to overeat. There are exceptions ofc, like nuts, but i think the general trend holds.

I believe you're basing that off of pseudoscience.

An ultra-processed food (UPF) is a grouping of processed food characterized by relatively involved methods of production. There is no simple definition of UPF, but they are generally understood to be an industrial creation derived from natural food or synthesized from other organic compounds.[1][2] The resulting products are designed to be highly profitable, convenient, and hyperpalatable, often through food additives such as preservatives, colourings, and flavourings.[3] UPFs have often undergone processes such as moulding/extruding, hydrogenation, or frying.[4]

https://en.wikipedia.org/wiki/Ultra-processed_food

What processes contribute to fat cells stocking lipids, and/or the replication of fat cells, and how do they relate to "ultraprocessed food"?

Which aspects of "ultraprocessed food" affect these processes, and which are harmless part of human food that has existed for thousands of years? Which aspects also affect "natural foods", such as pesticides and artifical hormones? Are there any studies supporting your hypothesis that aren't merely correlations based on socioeconomic biases?