The Facultative Carnivore Diet: Understanding Why Protein and Fat Support Human Biology is a physiology-first examination of how the human body is actually built, fed, and regulated. Instead of beginning with diet labels, calorie math, or modern food ideology, this book starts with anatomy, digestion, absorption, tissue repair, and metabolic signaling. It asks a simpler and more demanding question: what foods most directly support the structure and function of the human organism? Ian Miller argues that nutrition has been made confusing by abstraction. Foods are routinely judged by reputation, trend status, or nutrient labels while the body itself is treated like a black box. This book reverses that order. It shows how the stomach, pancreas, liver, gallbladder, small intestine, mitochondria, and endocrine system actually process food, and why protein and fat occupy a unique place in human biology. Amino acids build enzymes, muscle, connective tissue, immune molecules, and repair tissue. Fats support cell membranes, hormone production, nervous system structure, bile physiology, and stable long-duration energy.

The book explains why complete protein, natural fats, and nutrient-dense animal foods often align more closely with human needs than the modern processed food base of refined sugar, refined starch, industrial oils, and ultra-processed combinations. It explores appetite, satiety, insulin, leptin, energy partitioning, fat oxidation, ketone production, protein quality, organ meats, fat-soluble vitamins, and why biological compatibility is a more meaningful dietary standard than calories alone. Rather than framing plant foods as automatic dietary foundations, The Facultative Carnivore Diet evaluates them as context-dependent additions whose value depends on digestibility, preparation, host tolerance, metabolic condition, and what they displace in the diet. Throughout, the emphasis remains on biological yield: what the body can actually extract, absorb, use, and retain after the full digestive and metabolic event is over. Written for readers who want a first-principles understanding of nutrition, this book offers a structural case for rebuilding the diet around protein and fat, restoring metabolic stability, and feeding the human body according to its design rather than according to modern nutritional mythology.