But this approach misses a fundamental point. The obesity problem is best understood not as the result of the overconsumption of a single macronutrient, but from a skewing of the proportion of each macronutrient in our diet — notably the dwindling quantity of protein in processed food products. The paucity of protein relative to fats and carbohydrates in processed foods drives the overconsumption of total energy as our bodies seek to maintain a target level of protein intake.

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.