I think that feeding experiments show that protein, even in healthy people, provokes as sharp an insulin response as carbs (see the heading "MYTH: Carbohydrate Is Singularly Responsible for Driving Insulin"). Apparently, amino acids drive this insulin response directly, without first being converted to glucose. And apparently, glucagon that the body secretes during protein consumption doesn't cause fat to be released from cells to cancel insulin's effect on fat-burning. Since protein stimulates insulin secretion, it would cause a rapid drop in blood glucose if no carbohydrate is consumed with the protein. Glucagon prevents this rapid drop in blood sugar by stimulating the liver to produce glucose.

So, when Moore restricted his protein intake, he was reducing his glucagon production, and thereby reducing his glucose production, allowing lipolysis to occur.