Chapter 4 — Quiz

Twenty questions. Attempt each before opening.

Multiple Choice

1. When a person loses body fat, where does the mass physically go?

  • a) It is converted to muscle
  • b) It is excreted in urine and faeces
  • c) It is oxidized, leaving mostly as carbon dioxide through the lungs, with the rest as water
  • d) It is converted to heat and disappears
Answer **c.** You exhale the carbon. (a) is a common misconception — fat and muscle are different tissues and one does not become the other. (d) misunderstands conservation of mass.

2. Which component makes up the largest share of total daily energy expenditure for most people?

  • a) Exercise
  • b) Thermic effect of food
  • c) NEAT
  • d) Basal/resting metabolic rate
Answer **d.** BMR/RMR is ~60–70%. Deliberate exercise is typically the *smallest* of the four for most people — often 0–20%, and toward the bottom of that range for anyone with a desk job.

3. The thermic effect of food is highest for:

  • a) Fat
  • b) Carbohydrate
  • c) Protein
  • d) All macronutrients equally
Answer **c.** Roughly 20–30% of protein's energy is spent processing it, versus ~5–10% for carbohydrate and ~0–3% for fat. This is the genuine kernel of truth in "a calorie is not a calorie" — and it moves a whole diet's expenditure by a few percentage points, not a revolution.

4. "Eat less, move more" is criticized in this chapter primarily because:

  • a) It is factually incorrect
  • b) It describes an outcome rather than a mechanism, and contains no information about how
  • c) Exercise doesn't affect body weight
  • d) Energy balance doesn't apply to humans
Answer **b.** It's arithmetically correct — that's precisely the problem. It's the accounting identity, like telling an indebted person "your outgoings exceed your income."

5. In an energy deficit, NEAT typically:

  • a) Increases, as the body seeks food
  • b) Stays constant
  • c) Falls, largely unconsciously
  • d) Is unaffected because it isn't under hormonal control
Answer **c.** People in deficit fidget less, take fewer steps, stand less — and do not notice it happening. This is one of the largest and least-discussed reasons deficits underdeliver.

6. Doubly labelled water studies comparing measured expenditure to self-reported intake in weight-stable people consistently find that self-reported intake is:

  • a) Accurate to within about 5%
  • b) Substantially higher than expenditure
  • c) Substantially lower than expenditure, commonly by around 20% or more
  • d) Random, with no consistent direction
Answer **c.** And the gap tends to be larger in people with higher body weight and in people who know they're being observed. This is not lying — it applies to dietitians and researchers as reliably as to everyone else.

7. Six pounds lost in the first four days of a low-carbohydrate diet is mostly:

  • a) Fat
  • b) Muscle
  • c) Glycogen and the water bound to it
  • d) Gut contents only
Answer **c.** Each gram of glycogen is stored with roughly three grams of water. Depleting glycogen releases that water. It returns when carbohydrate returns — which is why post-diet regain looks so alarmingly fast and gets misread as metabolic damage.

8. The Hall ultra-processed food crossover trial is significant because it showed that:

  • a) Ultra-processed food contains more calories per gram
  • b) With calories, macronutrients, sugar, sodium and fiber matched and participants free to eat as much as they liked, people spontaneously ate substantially more on the ultra-processed menu
  • c) Calories don't matter
  • d) Processing destroys nutrients
Answer **b.** The food changed the intake, with the same people under the same instructions. Note (c) is exactly the wrong lesson — the effect operated *through* energy intake, which is the point.

9. A steady surplus of 100 kcal/day, ignoring adaptation, corresponds to roughly:

  • a) 1 lb/year
  • b) 10 lb/year
  • c) 50 lb/year
  • d) No weight change, as the body compensates fully
Answer **b.** 100 × 365 = 36,500 kcal ÷ ~3,500 ≈ 10 lb. Adaptation flattens this in reality, but the order of magnitude explains how someone gains 30 lb across a decade without ever feeling they overate.

10. The carbohydrate-insulin model of obesity, in its strong form, has been tested primarily by:

  • a) Observational cohort studies only
  • b) Controlled feeding studies holding calories and protein constant while varying carbohydrate and fat
  • c) Animal studies only
  • d) It has never been tested
Answer **b.** Those studies generally find little or no fat-loss advantage for the low-carbohydrate arm. The weaker version — that diet composition affects appetite and adherence — is well supported, and is most of what its advocates observe clinically.

11. Someone losing fat at 0.5 kg/week is trying to detect a daily signal of roughly 70 g against daily body-weight noise of roughly:

  • a) 5–10 g
  • b) 50–100 g
  • c) 1–2 kg
  • d) 10 kg
Answer **c.** The noise is more than ten times the signal. This is why daily weighing without averaging is sampling far faster than the underlying variable changes — and reacting to each sample.

12. The chapter's thermostat analogy replaces the balance-scale picture because:

  • a) The scale picture overstates the role of exercise
  • b) The scale picture wrongly depicts intake and expenditure as independent
  • c) The scale picture ignores the thermic effect of food
  • d) Balance scales are outdated
Answer **b.** In a bank account, income and spending are independent. In a body, a controller adjusts both in response to changes in either — which is why a 500 kcal deficit doesn't produce a 500 kcal deficit.

True / False

One-line justification.

13. Hormones can cause fat gain without an energy surplus.

Answer **False.** Stored energy must come from somewhere. Hormones powerfully influence appetite, expenditure, and partitioning — they operate *through* the equation, not around it. Some medical conditions and medications genuinely cause weight gain; they do so by changing intake, expenditure, or fluid, not by suspending physics.

14. Metabolic adaptation is a myth invented to excuse failed diets.

Answer **False.** It's real and measurable: resting rate falls somewhat beyond what reduced body size predicts, NEAT drops, and appetite hormones shift and stay shifted. It is also **modest** — measured in hundreds of calories, not thousands. Chapter 5 puts numbers on it.

15. You must count calories in order to lose weight.

Answer **False.** Counting is one effective strategy among several, not a requirement. Higher protein and fiber, reducing ultra-processed food, portion and environment changes, and eliminating one or two high-energy low-satiety items all produce deficits without counting — and for people with a history of disordered eating, counting is actively harmful.

16. A single large meal can meaningfully undo a month of consistent eating.

Answer **False.** A 1,200 kcal excess is roughly a third of a pound of fat; most of what appears on the scale next morning is food volume, sodium, and glycogen water. The genuine harm is the *"I've ruined it, so I may as well"* response, which converts a 1,200 kcal event into a 12,000 kcal week.

17. Because exercise is a small share of energy expenditure, it isn't worth doing.

Answer **False**, and this is the most important misreading available of §4.5. Exercise is extraordinarily good for you — cardiovascular health, insulin sensitivity, bone density, muscle retention during weight loss, mood, sleep, mortality — for reasons that have almost nothing to do with the calories it burns. What's unreliable is exercise *as a calorie-burning strategy*, and the "I earned this" framing that goes with it.

Short Answer

18. State both halves of the threshold concept and explain what error results from holding only one.

Answer **Half one:** energy balance is thermodynamically non-negotiable — stored energy came from food, and lost stores mean more left than arrived. **Half two:** that fact is a description of an outcome, not a mechanism you can operate, and unlike a bank account the two sides are coupled by a system defending your current state. **Holding only half one** produces the error of treating weight as arithmetic and therefore as a matter of discipline — "eat less, move more," delivered to someone who already knows. **Holding only half two** produces the error of believing calories are irrelevant and that some hormone, food, or protocol can produce fat loss without a deficit, which licenses every metabolic-magic claim in the industry.

19. Explain, using at least three distinct mechanisms, why a 500 kcal/day deficit does not produce 52 lb of weight loss in a year.

Answer Any three of: **(1)** A smaller body costs less to run, so the deficit shrinks each week without any change in behavior. **(2)** NEAT falls unconsciously, often by a large fraction of the intended deficit. **(3)** Adaptive thermogenesis — resting rate falls somewhat beyond what body size predicts. **(4)** Ghrelin rises and leptin falls, and these persist, degrading adherence over months for physiological rather than moral reasons. **(5)** The starting intake estimate was probably already low by more than 500 kcal (§4.7), so the deficit may never have existed as calculated. **(6)** The 3,500 kcal-per-pound rule is a simplification never intended for linear annual extrapolation. **Note what's absent from that list: willpower.**

20. A person's tracking app says they ate 1,650 kcal today. Describe honestly what that number means.

Answer It means their *recorded* intake, calculated from database values, summed to a false precision. Label tolerances permit meaningful deviation from stated content; portion estimates routinely err by 20–50%; cooking oil, drinks, and tastes are commonly omitted; restaurant items are guesses; and absorption varies with food form (§3.9). The realistic range for true intake is perhaps 1,650 to 2,100 or more, skewed upward, because underreporting is systematic rather than random. **Useful as a trend across weeks. Not meaningful as a daily verdict** — and the gap between 1,647 and 1,653 that the app displays does not exist.

Applied Scenario

21. A 41-year-old tells you: "I eat 1,400 calories a day, I walk 10,000 steps, and I've gained four pounds in the last month. My metabolism is broken and I think I need to eat even less."

What do you say, what do you want to know, and what would make you send them to a doctor?

Answer **First, don't dispute the 1,400.** Telling them they're wrong ends the conversation and is unkind, and you don't actually know. Ask them to walk you through a typical day, in the moment rather than retrospectively, including drinks, oil, tastes, and weekends. Most of the resolution appears here without anyone having to be accused of anything — Theo estimated 2,000 and ate 3,160, and he was being completely honest. **Second, address the four pounds directly.** Four pounds in a month, in someone eating at what they believe is a deficit, is very often not fat: it's water, glycogen, sodium, gut contents, cycle phase, a new exercise routine causing muscle inflammation, or a change in medication. Ask how they weighed — same time, same conditions, single reading or weekly average? Four pounds is inside the range of ordinary fluctuation (§4.9). **Third, address the plan.** "Eat even less" is the instinct and it is usually the wrong move: a larger deficit worsens NEAT suppression, worsens hunger, worsens adherence, and increases lean tissue loss. If a genuine deficit is warranted, smaller and sustained beats larger and abandoned. **Fourth, ask what else changed** — sleep, stress, a new medication, a new job, alcohol, an injury that reduced activity. **Send them to a doctor if:** intake is genuinely very low and verified with weight gain continuing; there are symptoms suggesting thyroid disease (fatigue, cold intolerance, hair changes, constipation); they've started a medication associated with weight gain (steroids, some antipsychotics, some antidepressants, some hormonal treatments); there is swelling suggesting fluid retention; or the weight change is rapid and unexplained. ⚠️ **Also** — and this is the one clinicians miss — if the way they talk about food and their body suggests restriction, compensation, or distress, that's a [Chapter 34](../../part-06-practical-nutrition/chapter-34-eating-disorders/index.md) conversation, and "eat even less" may be a symptom rather than a plan.

Scoring

Score Reading
18–21 You're holding both halves. That's harder than it looks — move on.
14–17 Solid. Reread §4.6 (the coupling) and §4.9 (weight vs. fat).
10–13 Reread §4.2 and §4.3 together, then §4.7. The threshold concept hasn't fully landed.
Under 10 Reread the chapter. Chapters 5, 10, 21, 22, and 24 all depend on this one.

And whatever you scored: do the three-day food diary. It is the single most informative thing in Part I, and reading about it is not a substitute.