“Excess consumption of dietary protein from the lean meats of wild animals leads to a condition referred to by early American explorers as “rabbit starvation,” which initially results in nausea, then diarrhea, and then death (39). Clinical documentation of this syndrome is virtually nonexistent, except for a single case study (42). Despite the paucity of clinical data, it is quite likely that the symptoms of rabbit starvation result primarily from the finite ability of the liver to up-regulate enzymes necessary for urea synthesis in the face of increasing dietary protein intake.” [Emphasis added]
A Word About Protein And Satiety
A number of studies have shown that when given energy-restricted diets, people find higher protein intakes more satiating (within meals) and satisfying (between meals) than lower protein diets. For a while I felt impressed by this, thinking that protein is more satiating than any other nutrient.
However, I now think this finding simply reflects the long-known fact that when when we restrict total food energy intake, and therefore carbohydrate intake, protein requirements increase, because carbohydrate restriction increases the use of lean mass to produce glucose. Thus, under hypocaloric conditions, a drive to meet increased protein requirements--what we might call "protein hunger"-- may surface.
Again, it has been known for a long time that protein requirements increase under hypocaloric conditions, so these recent studies showing higher protein diets to be more satiating under hypocaloric conditions appear to me to just be late application of something we have known for decades. These findings do not mean that protein is the most satiating nutrient under all conditions. I performed a quick PubMed search for studies of the satiating effects of protein under ad libitum conditions, and found only one study [6 abstract ] which reported both "higher protein led to greater daily fullness" and "Protein quantity did not influence daily hunger, glucose, or insulin concentrations," i.e. inconsistent effects.
Given what we know about the satiating power of carbohydrate and protein, and fat balance versus energy balance, Astrup suggests that the optimal diet for reducing body fat might be very low in fat, high in carbohydrate, and moderately high in protein, for example 60-65/20-25/15 carbohydrate/protein/fat [7 abstract, 8 full text].