>Now, if the food industry and nutrition scientists removed a lot of the animal fats, then both people's physical and emotional needs increased, and many searched for sugars and carbs to compensate. They are a poor substitute, though.

Anecdote. I've tested this personally and found it to be true. Gastric motility also increases with high animal fat diets, meaning on some level my body/brain feels like its getting what it requires faster.