Chapter 8 — Exercises

If you have a parent or grandparent over seventy, do B7 and C6. They are the two most consequential exercises in this book so far.

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

Selected answers in Appendix J.

Part A — Conceptual Understanding ⭐

A1. What are protein's three jobs? Which one is protein actually for?

A2. What is the RDA for protein, what does "RDA" formally mean, and why is it described as a floor?

A3. Explain the nitrogen balance method and name its three limitations. In which direction do those limitations bias the estimate?

A4. What is IAAO, and what do IAAO-based estimates suggest about adult protein requirements?

A5. Give reasonable g/kg targets for: a healthy sedentary adult · an older adult · someone resistance training · someone in an energy deficit · someone with chronic kidney disease.

A6. How many amino acids build human proteins? How many are essential? What does "complete" mean?

A7. Compare PDCAAS and DIAAS. Why is the cap on PDCAAS a problem?

A8. What is leucine's special role, and roughly what dose triggers it?

A9. Where did the protein-combining rule come from, and what happened to it?

A10. What is the muscle protein synthesis plateau, and what did the "30 g per meal" claim confuse it with?

A11. How long is the "anabolic window" actually, and what variable dominates?

A12. Define anabolic resistance and sarcopenia. Why do they mean requirements rise with age?

A13. Why is the acid-ash hypothesis considered overturned, and what does the outcome evidence show?

Part B — Applied Analysis ⭐⭐

B1. Calculate g/kg and identify the gap for: (a) 70 kg adult eating 55 g; (b) 95 kg lifter eating 120 g; (c) 52 kg older woman eating 40 g; (d) 60 kg athlete in a deficit eating 75 g.

B2. Theo weighs 96 kg, eats 118 g of protein, and his target is 1.6 g/kg. Calculate his gap. Then design three changes to close it, with estimated grams for each, using only whole foods.

B3. A 25-year-old and a 78-year-old each eat 20 g of protein at breakfast. Explain why this is adequate for one and not the other.

B4. Someone eating a plant-based diet asks whether they need to combine rice and beans at the same meal. Answer in three sentences — including the part of the concern that is legitimate.

B5. A trainer tells a client that eating more than 30 g of protein at dinner is wasted. Correct this, distinguishing precisely between what's true and what's confused.

B6. A client with type 2 diabetes and normal kidney function is worried that 1.6 g/kg will damage their kidneys. Address the concern, and say what would change your answer.

B7. Your grandmother, 81 kg 74 years old, eats: tea and toast; a small sandwich; soup and bread; occasional biscuits. Estimate her protein intake, calculate her target, and write the three changes you'd actually suggest — each costing under $1/day and requiring no new cooking skill.

B8. Devi (55 kg, vegetarian, energy deficit, 61 g protein) and a 55 kg sedentary omnivore both want to reach "adequate" protein. Explain why their targets differ and by how much.

Part C — Skills & Practice ⭐⭐–⭐⭐⭐

C1. Do the protein audit. The Project Checkpoint: total, g/kg, target, gap, per-meal distribution, top five sources with cost, and one change with a likelihood rating.

C2. The breakfast test. Calculate the protein in your typical breakfast using the §8.12 table. If it's under 20 g, redesign it three different ways — one using eggs, one using dairy, one using neither. Cost each one.

C3. Build a 100 g day. Using only the §8.12 table and whole foods, construct a day reaching 100 g of protein with at least 25 g at three separate meals. Then do it again on half the budget.

C4. Cost per 20 g. In an actual shop, price ten protein sources and calculate cost per 20 g of protein for each. Include at least one protein bar and one legume. Rank them.

C5. Read three protein-claim products. Find three products marketed on protein content (bar, drink, cereal, snack). For each record: protein per serving · cost per 20 g protein · added sugars · sugar alcohols · ingredient count. Compare each to an equivalent whole food.

C6. Ask an older relative. Ask a parent or grandparent over 70 what they ate yesterday. Estimate the protein. Compare to 1.0–1.2 g/kg. Then have a conversation about it — and notice how hard it is to raise, and what beliefs come up. (This exercise makes people uncomfortable and is the most valuable one in the chapter.)

C7. Find the leucine threshold. Using the §8.12 table, identify how much of each of these you'd need to reach roughly 25–30 g of protein in one sitting: Greek yogurt · lentils · eggs · tofu · chicken. Which are realistic portions and which aren't?

Part D — Synthesis & Critical Thinking ⭐⭐⭐

D1. The RDA is a minimum communicated as a recommendation. Is that a communication failure, a documentation failure, or an unavoidable feature of population guidance? How would you fix it, and what would break?

D2. IAAO studies suggest higher requirements than nitrogen balance, and the RDA hasn't changed. Is that appropriate conservatism (Chapter 2 rung 8) or institutional inertia? What would justify a change?

D3. The chapter says higher protein is well supported for muscle and function, and that the longevity evidence is contested — possibly favouring lower protein in midlife. How should someone act under that uncertainty? Does the answer differ at 40 and at 75?

D4. Protein powder is described as "food in a convenient form" and given a 🟡. A critic says this is too generous — that the industry sells necessity, not convenience, and the verdict launders that. A defender says the product genuinely works. Adjudicate.

D5. Ruth believed "at my age you don't need much." Where does that belief come from, and why is it so durable? Design a public health message that would actually shift it — then explain why it hasn't been run.

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

M1. (With Chapter 6.) Explain, using the amino acid pool and protein turnover, why meal-by-meal protein combining is unnecessary. Then explain why distribution across the day might still matter a little.

M2. (With Chapter 6.) Devi is in an energy deficit doing 60 miles a week. Using gluconeogenesis (§6.7) and the absence of a protein store (§6.2), explain why her protein requirement is elevated beyond what her training alone would suggest.

M3. (With Chapter 4.) Why does protein intake go up in an energy deficit? Name all three mechanisms and say which one actually matters most.

M4. (With Chapters 4 and 5.) Two people lose 10 kg. One loses 1 kg of lean tissue, the other 3.5 kg. Using Chapter 4 §4.9 and Chapter 5 §5.2, explain what differs in their outcomes, their subsequent metabolic rate, and what the scale showed.

M5. (With Chapter 2.) The MPS dose-response studies are the basis for most protein timing advice. Identify what kind of endpoint MPS is, place it on the evidence ladder, and explain why the outcome trials are less impressed than the mechanism.

M6. (With Chapter 7.) Compare the carbohydrate RDA (130 g) and the protein RDA (0.8 g/kg). Both are described as misleading if read as targets — but for opposite reasons. Explain both.

M7. (With Chapter 5.) Muscle costs ~13 kcal/kg/day at rest (§5.2), so gaining muscle barely raises RMR. Given that, construct the strongest evidence-based case for resistance training that doesn't mention metabolism at all.

Part E — Research & Extension ⭐⭐⭐⭐

E1. Find the DRI chapter on protein (National Academies, 2005) and read how the 0.8 g/kg figure was derived. Then find IAAO-based estimates. Write a page on why the two methods disagree and what would be needed to revise the RDA.

E2. Read the PROT-AGE working group recommendations and/or the ESPEN guidance on protein in older adults. What do they recommend and why? Then look for how widely these have been adopted in clinical practice and in public messaging — the gap is the interesting part.

E3. Find the 1971 and 1981 editions of Frances Moore Lappé's Diet for a Small Planet, or accounts of the change. Read what she wrote in the later edition about the combining scheme. Then search for how often the combining rule still appears in current materials. A retraction that didn't propagate for forty years is a case study in itself.

E4. Investigate the protein and longevity literature — including work associating lower protein or lower mTOR signalling with lifespan in model organisms, and the human observational data that appears to differ by age. Where does the disagreement sit, and what would resolve it?

E5. Look into DIAAS and its adoption. Why hasn't it replaced PDCAAS in labelling? Who benefits from the cap on PDCAAS, and who from its removal? (Follow the money in both directions — Chapter 1 §1.5.)

E6. Read the evidence on resistance training plus protein for sarcopenia in older adults. How large are the effects on strength and function, and what's the minimum effective training dose? Then consider why this intervention, which is cheap and well supported, is so rarely prescribed.