Chapter 9 — Exercises

Part D is unusually important here. This is the chapter where being skeptical is most likely to lead you into the same error as the guidance you're skeptical of.

Difficulty legend: ⭐ basic recall · ⭐⭐ applied · ⭐⭐⭐ synthesis and judgment · ⭐⭐⭐⭐ extension

Selected answers in Appendix J.

Part A — Conceptual Understanding ⭐

A1. What does "saturated" actually mean chemically? What physical property does it produce, and why?

A2. Give the approximate saturated fat percentage of butter and of olive oil. What's the general point?

A3. Summarize the current evidence position on each of the four fat types in one line each.

A4. What are industrial trans fats, what did they do to blood lipids that no other fat does, and what happened regulatorily?

A5. What was the Seven Countries Study? What is the "cherry-picked 22 countries" claim, and what is actually true about it?

A6. Complete the substitution table: replacing saturated fat with PUFA, MUFA, whole grains, and refined carbohydrate — what happens to cardiovascular risk in each case?

A7. Why did the 2015–2020 Dietary Guidelines drop the 300 mg dietary cholesterol limit? Name the three complications the chapter attaches to that.

A8. Which two fatty acids are essential? How well does ALA convert to EPA and DHA?

A9. State the omega-6/omega-3 ratio hypothesis, and say what the human evidence shows about it.

A10. Name the four omega-3 trials discussed and their results. Why do REDUCE-IT and STRENGTH disagree?

A11. What is ApoB, and why does it predict risk better than LDL-C?

A12. Why is HDL described as "a marker, not a lever"?

A13. Which matters more for cooking oil selection — smoke point or oxidative stability? Why?

Part B — Applied Analysis ⭐⭐

B1. Theo's folder contained two contradictory saturated fat headlines. Explain, in four sentences, how both are accurate — naming the specific comparator each is using.

B2. For each substitution, predict the direction of effect and state your confidence: (a) butter → olive oil; (b) butter → low-fat biscuits; (c) full-fat yogurt → fat-free sweetened yogurt; (d) beef → lentils; (e) beef → chicken.

B3. Coconut oil raises HDL and contains "MCTs." Explain, in three sentences, why neither fact supports the health claim.

B4. A friend takes 1 g/day fish oil for heart health and eats no fish. Using §9.8 and the cost check, assess this. What would you suggest instead, and at what cost?

B5. Someone has an LDL-C of 110 mg/dL and considers themselves fine. Using §9.10, name one test that might change the picture and explain why.

B6. Explain why Mendelian randomization is unusually powerful evidence for LDL's causal role, using the "dose × time" framing from the artery diagram.

B7. A cook asks whether to buy avocado oil for "healthier high-heat cooking." Answer honestly, including the question they should have asked instead.

B8. Ruth was told to cut eggs and cheese in about 2016. Assess that advice against current evidence, and then assess it against her specific situation from Chapter 8. Are those the same assessment?

Part C — Skills & Practice ⭐⭐–⭐⭐⭐

C1. Do the fat audit. The Project Checkpoint: total and percentage, saturated/unsaturated source split, the substitution question applied to your two largest saturated sources, omega-3 servings, what you cook in, and one change with a likelihood rating.

C2. Answer the substitution question honestly. For your two biggest saturated fat sources, write down what would actually replace them if you cut back — not what should, what would. If the honest answer is refined carbohydrate, the change isn't worth making.

C3. Read six fat labels. Six products in your kitchen containing meaningful fat. Record total fat, saturated fat, and whether the ingredient list contains "partially hydrogenated" anything. Rank by saturated fat percentage of total fat.

C4. Price your omega-3. Cost out four routes: tinned sardines twice a week, tinned mackerel, frozen salmon, and standard fish oil capsules. Calculate annual cost for each. Then decide.

C5. Trace the "Keys cherry-picked" claim. Find three sources making this claim. For each, note whether they distinguish the Seven Countries Study from the Yerushalmy and Hilleboe 22-country analysis. Count how many get it right. This is a skepticism-checking exercise, not a defend-the-mainstream one.

C6. Change your cooking oil. If you don't already cook primarily in olive oil, do it for two weeks. Note cost difference, taste difference, and whether anything about your cooking actually changed. This is the lowest-friction dietary change in the entire book.

C7. Ask for ApoB. At your next lipid panel, ask whether ApoB can be added. Note the response, the cost, and whether it was already available. (This exercise is partly about learning what your health system will and won't do when asked.)

Part D — Synthesis & Critical Thinking ⭐⭐⭐

D1. Do the 🧩 national-campaign problem from §9.5 properly if you skipped it. Then answer the harder question: what evidence would distinguish explanation A from explanation D? Is such evidence obtainable?

D2. The chapter says the "cherry-picked seven countries" claim is a garbled version of a real critique, and calls out repeating it as the same error the book is against — "including when it's aimed at a target I might otherwise be sympathetic to." Is that even-handedness, or is it defending the establishment? Argue both.

D3. The Minnesota and Sydney trials lowered cholesterol without improving mortality. Construct the strongest case that they overturn the diet-heart hypothesis. Then construct the strongest case that they don't. Which do you find more persuasive, and what would change your mind?

D4. Trans fats are described as "the one where the system worked" — and it took decades and cost lives. Is that a success story or an indictment? Can it be both? What would a faster system have required, and what would that system get wrong?

D5. The chapter ends: "If you finish this chapter irritated with both, you have understood it." Is irritation with both camps a sign of good calibration, or is it a form of false balance that avoids committing? Distinguish the two.

Part M — Mixed & Interleaved Practice ⭐⭐–⭐⭐⭐

M1. (With Chapters 1 and 2.) Theo's saturated fat headline pair was Chapter 1's opening puzzle. Using Chapter 2's Claim Filter, work through both articles formally. Which of the six questions resolves it?

M2. (With Chapter 2.) The Minnesota and Sydney trials illustrate a specific Chapter 2 concept. Name it, then find one other example of the same concept elsewhere in this book.

M3. (With Chapter 3.) Explain why blood triglycerides rise for hours after a fatty meal, using the absorption route from Chapter 3 §3.4.

M4. (With Chapter 7.) Chapter 7 said the low-fat era failed because of what replaced the fat. This chapter's substitution table makes the same point quantitatively. Write the single sentence that unifies Chapters 7 and 9.

M5. (With Chapter 8.) Ruth's egg-and-cheese advice is a Chapter 9 issue that caused a Chapter 8 problem. Trace the causal chain, and state the general lesson about how dietary advice ages.

M6. (With Chapter 6.) Why does fat provide 9 kcal/g? Answer using the hydroelectric dam image. Then connect it to why fat is the "high-capacity, low-rate" fuel.

M7. (With Chapter 5.) Someone claims coconut oil "boosts metabolism" because of MCTs. Combine §9.11's verdict with Chapter 5's percentage-to-calories technique to answer in two sentences.

M8. (Revisit at Chapter 19.) Write down now what you expect the seed oil verdict to be, and what evidence would have to exist for it to go the other way. Seal it.

Part E — Research & Extension ⭐⭐⭐⭐

E1. Read a Cochrane review on reducing saturated fat intake. Note the effect size, the certainty rating, and — most importantly — how the reviewers handle the comparator problem. Then compare their conclusion to how the review was reported in the press.

E2. Find the re-analyses of the Minnesota Coronary Experiment and the Sydney Diet Heart Study, and at least two critiques of those re-analyses. Where exactly does the disagreement sit — the data, the methods, the missing information, or the interpretation?

E3. Read the primary literature on REDUCE-IT and STRENGTH, plus the published debate about the mineral oil placebo. Write a page on what would resolve it and whether that trial will be run.

E4. Investigate ApoB versus LDL-C as risk predictors. Why hasn't ApoB replaced LDL-C in routine lipid panels? Consider cost, inertia, guideline processes, and who would have to change practice.

E5. Read the AHA Presidential Advisory on dietary fats and cardiovascular disease (2017), including its treatment of coconut oil. Then find a critical response to it. Assess both against §9.5's substitution frame — do either of them state the comparator clearly?

E6. Investigate the history of partial hydrogenation — how margarine came to be recommended, when the evidence turned, and how long regulatory action took. Construct a timeline. Then ask what a present-day equivalent might be, and how you'd know.