Like many other animals, humans have what biologists call a "dominant appetite" for protein. The biological drive for protein is so strong that a cricket who feels short of protein will resort to cannibalism. When a locust is short of protein, it will explore different food sources to redress the balance. Humans are neither as ruthless as crickets nor as prudent as locusts. When given access to a diet that is low on protein and heavy in carbs and fats, humans will binge, in an attempt to extract the protein they need.
If many of us overeat, it could be partly because our bodies are desperately seeking out protein in a food environment flooded with refined wheat and oils and many kinds of sugar. As Raubenheimer and Simpson wrote in their startlingly original 2012 book
The Nature of Nutrition: "Dilution of protein in the diet by fat and carbohydrate drives excess consumption, perhaps more so in some individuals, life stages and populations than others." In other words, obesity may often really be hunger hiding in plain view.