Part II — Macronutrients

Chapters 7–12

Three substances in your food carry essentially all of its energy: carbohydrate, protein, and fat. A fourth — alcohol — carries energy too, and gets its own chapter for reasons that will become uncomfortable. That's the whole list. Everything else you eat is water, fiber, or measured in milligrams.

You would not guess this from the last forty years of public discourse, during which each of the three has taken a turn as the villain, been rehabilitated, and in at least one case been villainized again by a new generation that didn't know the first round had happened.

  • Fat was the enemy from roughly 1980 to 2000. Supermarkets filled with low-fat products that replaced the fat with sugar, and everyone got fatter.
  • Carbohydrate took over as the enemy around 2000 and has held the title, with brief interruptions, ever since. Atkins, then South Beach, then paleo, then keto, then carnivore.
  • Protein never became the villain, which is itself interesting, and is currently enjoying a status so unimpeachable that it's being added to breakfast cereal and bottled water.

Each of these eras was driven by real findings, badly generalized. Each produced a food supply reshaped around the fear, which caused problems that fed the next era. And in each era, the honest answer — that the type and the context and the thing it replaced matter far more than the category — was available and unmarketable.

What this part does

Six chapters, one per macronutrient plus two that couldn't be avoided:

Chapter 7 — Carbohydrates. Sugars, starches, fiber. Why "simple versus complex" is a nearly useless distinction and "intact versus refined" is a genuinely useful one. Glycemic index and glycemic load, and why both are weaker predictors than the apps promise. Resistant starch. And the question that surprises everyone: how much carbohydrate does a human require? The answer is not what either side of the diet wars wants it to be.

Chapter 8 — Protein. The RDA versus what's optimal, which are different questions with different answers. Grams per kilogram for different goals. Complete and incomplete protein, and why the protein-combining rule you may have learned was overturned decades ago and still won't die. Leucine, muscle protein synthesis, and the "anabolic window," which is several hours wide rather than thirty minutes. Plant versus animal. And whether high protein damages kidneys or bones, which in healthy people it does not.

Chapter 9 — Fat. 🪞 The most historically fraught chapter in the book. Saturated, monounsaturated, polyunsaturated, trans. Omega-3 and omega-6. The diet-heart hypothesis — including, honestly, the parts that were overstated and the parts that held up under fifty years of attack. Dietary cholesterol versus blood cholesterol. And the substitution question, which reorganizes the entire debate the moment you take it seriously.

Chapter 10 — The Diet Wars. 🚪 Low-carb versus low-fat versus Mediterranean versus vegan versus paleo versus carnivore, judged by the standards of Chapter 2 rather than by which side has better content. What the head-to-head trials show (much less difference than either camp claims). What survives at two years. And the threshold concept that resolves the whole argument: adherence beats composition, and the winning diets have more in common than their advocates will admit.

Chapter 11 — Fiber. The nutrient with the best evidence-to-attention ratio in the entire food supply. Soluble, insoluble, viscous, fermentable. Short-chain fatty acids. Effects on cholesterol, glucose, satiety, transit, and mortality that are large, consistent, and almost entirely unmarketed, because nobody can patent a bean. Most people get about half of what they should. This is, quietly, the highest-yield chapter in Part II.

Chapter 12 — Alcohol. 🪞 The honest assessment, which is less comfortable than the version you've heard. Where the J-curve came from and why it's probably an artifact of who ends up in the "non-drinker" group. What Mendelian randomization added. The IARC Group 1 classification. The calories nobody counts. And how to make your own decision as an adult without being lectured at, which is what the rest of the literature on this topic mostly does.

The rule that runs through all six chapters

You cannot remove a food from a diet without something taking its place.

This sounds trivial. It is the single most clarifying idea in macronutrient science, and almost every popular claim ignores it.

"Is butter bad for you?" has no answer. Compared to what? Replace butter with olive oil and one thing happens to your blood lipids. Replace it with refined carbohydrate and something quite different happens. Replace it with nothing and you have described an impossible diet.

Every time you meet a macronutrient claim in these six chapters, the first question is not is it bad but compared to what, in whom, for how long — the question from Chapter 2, which you will now use approximately four hundred times.

What you'll be able to do at the end of Part II

  • Explain what each macronutrient does, in what forms, and why type matters more than category
  • Estimate your own intake of each and compare it against evidence-based targets
  • Answer "should I go low-carb?" with a question rather than a position
  • Explain why the protein-combining rule is wrong without insulting the person who told you it
  • Describe the actual state of the saturated-fat evidence, including the genuine uncertainty
  • Say why fiber is the most underrated thing in the food supply, and increase yours without misery
  • Make an informed personal decision about alcohol based on what the evidence actually shows

And six more Framework components: a carbohydrate audit, a protein audit, a fat audit, a diet-history autopsy, a fiber ramp plan, and an honest alcohol count.

Start with the one that got demonized worst.

Chapters in This Part