Interesting article about our current obesity crisis being the result of protein-poor food =
As long as the animal eats the foods that it evolved to consume, this balance is maintained. The trouble comes when it eats a diet with a disproportionate quantity of a particular macronutrient, either because of a lack of appropriate foods in the environment or because its appetite control systems have been fooled or subverted. This is now happening in humans, as we live in a foodscape scarcely recognizable to our forebears.
In humans, as in many other animals, the appetite prioritizes protein over carbohydrate or fat2. The evolutionary explanation is straightforward: eating too little protein compromises growth, development and reproduction.