Simpson and Raubenheimer, the two scientists who came up with the protein leverage hypothesis of obesity, expound on their ideas in Nature.
The weight of evidence indicates that the primary driver of the obesity epidemic in recent decades has been increased intake, rather than decreased energy expenditure. Not surprisingly, much research has focused on the source of these extra calories, with vigorous debate over whether fats or carbohydrates (especially refined sugar) are the main culprits.
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.
In essence, foods that are “dilute” in protein make us eat more calories so as to satisfy protein requirements. This study reported that a 1% increase in protein intake was associated with 30 to 50 calorie lower food intake daily.
The range of processed food becoming available is evolving faster than our appetite control systems. Simple sugars and fat were rare in our ancestral environment and highly prized. This may be why modern humans tend to favour the fatty and sugary foods that now surround us, and would also account for the trend in agriculture and industrialization towards producing readily digested carbohydrates and fats.
Populations accustomed to a high-protein diet, such as hunter-gatherers, may be most at risk in moving to a modern diet where protein is in short supply. If their physiology reflects their ancestral diet, they may have appetite systems that strive for an even higher protein intake than populations whose ancestors switched earlier to an agricultural lifestyle with a high-carbohydrate diet.
Protein appears to be the food that produces the most satiety. On that basis, it seems that increasing protein in the diet would be helpful in losing weight. And in fact virtually all of the clinical studies show this.