Chapter 5 — Quiz

Nineteen questions. Attempt before opening.

Multiple Choice

1. Roughly what share of resting energy expenditure is accounted for by the brain, liver, heart, and kidneys combined?

  • a) ~10%
  • b) ~25%
  • c) ~55–60%
  • d) ~85%
Answer **c.** Those four organs are about 5–6% of body mass and do the majority of the resting burning. Your liver alone costs more per day than all forty percent of you that is skeletal muscle.

2. The approximate resting energy cost of skeletal muscle is:

  • a) ~110 kcal/kg/day
  • b) ~50 kcal/kg/day
  • c) ~13 kcal/kg/day
  • d) ~4.5 kcal/kg/day
Answer **c.** About 6 kcal per pound per day. (d) is adipose tissue. The popular "50 kcal per pound of muscle" figure is off by roughly an order of magnitude.

3. Mifflin-St Jeor for a 34-year-old man, 178 cm, 96 kg, gives an RMR of approximately:

  • a) 1,450 kcal/day
  • b) 1,908 kcal/day
  • c) 2,670 kcal/day
  • d) 3,160 kcal/day
Answer **b.** (10 × 96) + (6.25 × 178) − (5 × 34) + 5 = 960 + 1,112.5 − 170 + 5 = 1,907.5. Note (c) is Theo's *TDEE* after the 1.4 activity factor, and (d) is his measured intake.

4. The least reliable part of a typical TDEE calculation is:

  • a) The weight measurement
  • b) The Mifflin-St Jeor equation itself
  • c) The activity factor
  • d) The height measurement
Answer **c.** It's selected from a dropdown on the basis of subjective self-assessment, with 10–15% gaps between adjacent options — and the biggest real source of variation it's meant to capture, NEAT, is unconscious and therefore not reportable.

5. After losing 15 kg, someone's RMR is 250 kcal/day lower. Most of that drop is due to:

  • a) Adaptive thermogenesis
  • b) Simply being a smaller body
  • c) Thyroid suppression
  • d) Loss of brown adipose tissue
Answer **b.** Roughly 150–200 kcal of the drop is expected from reduced tissue mass. The genuinely adaptive component is the remainder — perhaps 50–100 kcal/day, and even that estimate is uncertain.

6. A respiratory quotient of approximately 0.8 in a resting person indicates:

  • a) They are burning only fat
  • b) They are burning only carbohydrate
  • c) They are burning a mixture, leaning toward fat
  • d) The measurement is faulty
Answer **c.** And it's the preview of Chapter 6: **there is no switch.** A resting human is burning both continuously, in a ratio that shifts with recent intake, exercise intensity, and time since eating.

7. Which of these genuinely and meaningfully increases TDEE?

  • a) Eating six small meals instead of three
  • b) A green tea extract supplement
  • c) Increasing daily walking and general movement
  • d) Drinking cold water
Answer **c.** NEAT is the largest modifiable component of TDEE, it's free, and it dwarfs every thermogenic product ever marketed. The others are real but trivially small (b, d) or nonexistent as metabolic effects (a).

8. Eating six small meals rather than three, at the same total intake, produces:

  • a) A higher total thermic effect of food
  • b) Essentially the same total thermic effect of food
  • c) A lower resting metabolic rate
  • d) Substantially more fat loss
Answer **b.** TEF is proportional to how much you eat, not how often. Meal frequency may matter for appetite and adherence — in both directions, depending on the person — but that's behavioral, not metabolic.

9. Between-person variation in RMR that cannot be explained by size, composition, age, or sex is approximately:

  • a) ±1%
  • b) ±10%
  • c) ±35%
  • d) ±60%
Answer **b.** Real, and worth taking seriously — for a 1,800 kcal RMR that's ±180 kcal/day, which is a genuine and unfair difference. It is also not an explanation for a 1,000 kcal discrepancy.

10. Which condition genuinely lowers resting metabolic rate and is diagnosed with a simple blood test?

  • a) Irritable bowel syndrome
  • b) Hypothyroidism
  • c) Lactose intolerance
  • d) Iron deficiency without anemia
Answer **b.** TSH ± free T4. The chapter's rule: "my metabolism is broken" deserves a blood test before it deserves a rebuttal.

11. The main limitation of the televised weight-loss competition follow-up study is that:

  • a) It didn't measure metabolic rate
  • b) It was small, uncontrolled, and studied an extreme intervention that doesn't generalize
  • c) Its findings have been retracted
  • d) It found no metabolic adaptation
Answer **b.** Its strength is that it *measured* rather than estimated — indirect calorimetry and body composition, six years out. It supports strong claims about extreme interventions and weak claims about everyone else.

12. Indirect calorimetry works by measuring:

  • a) Heat given off by the body directly
  • b) Oxygen consumed and carbon dioxide produced
  • c) Core body temperature over time
  • d) Blood glucose clearance rate
Answer **b.** Burning fuel consumes O₂ and produces CO₂ in known ratios, so the gases let you calculate energy release — and their *ratio* (RQ) tells you which fuel. (a) is direct calorimetry, which exists and costs a fortune.

True / False

One-line justification.

13. Your metabolism slows dramatically in your thirties.

Answer **False.** Expenditure adjusted for body composition is relatively stable through most of adult life, with meaningful decline arriving considerably later. What happens in your thirties and forties is usually muscle loss, fat gain, and less activity — a smaller engine and less driving, not a broken engine.

14. In a genuine, substantial energy deficit, weight loss can stop entirely.

Answer **False.** Sustained severe restriction produces weight loss — observed in famine, illness, and the Minnesota Starvation Experiment. What actually happens at very low reported intakes is that expenditure falls somewhat, hunger becomes overwhelming, and adherence collapses.

15. Metabolic adaptation is an excuse invented to explain failed diets.

Answer **False.** It's real, measurable, and persistent — and modest, on the order of tens to a few hundred kcal/day, scaling with the severity of the deficit. That's an argument for moderate deficits, not for futility.

16. A measured metabolic test at a gym gives you your TDEE.

Answer **False.** It gives you RMR. You still multiply by an activity factor from a dropdown, which reintroduces the largest source of error in the calculation. You've paid to improve the more accurate half of a two-part estimate.

17. Resistance training isn't worth doing for body composition, since muscle only adds ~6 kcal/lb to RMR.

Answer **False**, and this is the most important misreading of §5.2. Resistance training preserves lean mass during weight loss — largely determining whether you end up lighter-and-stronger or lighter-and-weaker — improves insulin sensitivity, protects bone, and preserves function in later life. None of those reasons is the RMR increase.

Short Answer

18. Renata used an online calculator (1,850), ate "about 1,500" for four months, lost seven pounds then nothing, and concluded her metabolism was broken. Address each of her four pieces of evidence.

Answer **The 1,850** carries a ±10% error bar before the activity multiplier — her true requirement could be 1,700 or 2,100. **The "about 1,500"** is an estimate from the same machinery that produced Theo's 2,000 against an actual 3,160; underreporting is systematic in everyone. **The seven-pounds-then-nothing** is §4.9: the early loss was largely glycogen and its bound water, after which the real fat-loss signal (~70 g/day) is buried in 1–2 kg of daily noise. **The taller friend** almost certainly does need more, because body size dominates RMR. And her mother's theory is partly right: unexplained between-person variation is real, about ±10%, or ~180 kcal/day for Renata — a genuine disadvantage, and not the explanation for what she's experiencing.

19. Explain why a resting respiratory quotient of ~0.8 undermines the "fat-burning zone" concept before you've read anything about metabolic pathways.

Answer RQ 0.7 is pure fat, RQ 1.0 is pure carbohydrate, and a resting human sits around 0.8 — a mixture. **You are always burning both.** There is no state in which you burn one fuel exclusively and no switch that flips between them; there is only a ratio that shifts continuously with intensity, recent intake, and time since eating. So the "fat-burning zone" isn't describing a mode you enter. It's describing an intensity at which the *proportion* of energy from fat is higher — which is true, and which says nothing about the *total* fat oxidized, because higher intensities burn more total energy. Chapter 6 works this through properly.

Applied Scenario

20. A 52-year-old woman, 163 cm, 79 kg, tells you she has been eating 1,300 kcal/day for five months and has gained 3 kg. She is exhausted, always cold, and her hair has been thinning. She started a new medication four months ago. She wants to drop to 1,000 kcal/day.

Calculate what's calculable, say what you'd do, and say what you would not do.

Answer **Calculate:** Mifflin-St Jeor = (10 × 79) + (6.25 × 163) − (5 × 52) − 161 = 790 + 1,018.75 − 260 − 161 = **1,387.75 ≈ 1,388 kcal/day**, range roughly **1,249–1,527**. Her reported intake of 1,300 is **below her estimated RMR**, before any activity at all. On the arithmetic alone this should produce weight loss, and it hasn't. **What I'd do — and the order matters.** This is a ⚠️ **§5.11 presentation, not a diet question.** Fatigue + cold intolerance + hair thinning is a classic hypothyroid symptom cluster, and it is diagnosed with a straightforward blood test. Separately, a new medication four months ago, with weight gain beginning after it, demands a medication review — several classes cause genuine weight gain. There's also a question about fluid: 3 kg over what period, and is there any swelling? So: **refer to a physician this week, with the food diary in hand.** Ask her to bring three days of real recorded intake, because a clinician working from actual data can do far more than one working from "I don't eat much." **What I would NOT do:** - **Not reduce her to 1,000 kcal.** That would deepen a deficit that is already below her estimated RMR, worsening lean tissue loss, NEAT suppression, and hunger — and it would delay the diagnosis while she blames herself for another failure. - **Not assume she's underreporting.** She might be — she might well be. But the symptom cluster is the signal here, not the number, and assuming underreporting is exactly the failure mode §5.11 warns about: eventually you miss a treatable illness in someone who has been telling the truth all along. - **Not tell her her metabolism is fine.** I don't know that yet, and in her case it may genuinely not be.

Scoring

Score Reading
17–20 Strong. You can now defuse most metabolism claims with arithmetic.
13–16 Good. Reread §5.2 (the organ table) and §5.6 (adaptation).
9–12 Redo Exercise C1 by hand and reread §5.3–§5.4. The error bars are the point.
Under 9 Reread the chapter. Chapters 6, 21, 23, and 24 build on it.