Chapter 5 — Exercises

Part C is arithmetic, and doing it by hand once is worth more than a hundred calculator visits.

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

Selected answers in Appendix J. Formulas in Appendix B.

Part A — Conceptual Understanding ⭐

A1. Define BMR, RMR, TEF, and TDEE. Which one do calculators estimate, and which one do people actually want?

A2. Which four organs account for roughly 55–60% of resting energy expenditure, and what share of body mass are they?

A3. What is the approximate resting energy cost of skeletal muscle, per kilogram per day? What about adipose tissue?

A4. Write out the Mifflin-St Jeor equation for men and for women from memory.

A5. What is the approximate error bar on a Mifflin-St Jeor estimate, and what happens to accuracy at the extremes of body composition?

A6. Name the four factors that genuinely vary between people's metabolic rates, ranked by how much they matter.

A7. Distinguish the two reasons energy expenditure falls after weight loss. Which one is "adaptation"?

A8. What is the respiratory quotient, and what do values of 0.7, 0.85, and 1.0 indicate?

A9. What is actually true and what is false in the popular concept of "starvation mode"?

A10. Name three medical conditions and three medication classes that can genuinely affect body weight.

Part B — Applied Analysis ⭐⭐

B1. Calculate Mifflin-St Jeor RMR for: (a) a 45-year-old woman, 165 cm, 72 kg; (b) a 58-year-old man, 180 cm, 105 kg; (c) a 23-year-old woman, 158 cm, 51 kg. Show every line. Then give each one's ±10% range.

B2. Take your answer to B1(a) and produce TDEE estimates at activity factors 1.2, 1.375, and 1.55. How far apart are the extremes, in calories? What does that tell you about which part of the calculation deserves the most care?

B3. A trainer claims a client will "add 400 calories a day to their metabolism" by gaining 8 lb of muscle over six months. Evaluate the claim numerically. Then write the version of the claim that is actually true — and list three genuine reasons the client should train anyway.

B4. Renata's calculator said 1,850 and she ate "about 1,500" for four months, losing seven pounds then nothing. Give three separate explanations for the plateau, ranked by likelihood. For each, say what evidence would confirm or rule it out.

B5. A supplement advertises "increases metabolic rate by up to 11%." For a person with an RMR of 1,450, convert this to calories. Compare it to (a) the error bar on their RMR estimate, (b) one banana, and (c) a twenty-minute walk. What do you conclude?

B6. Someone loses 12 kg. Estimate how much of the resulting drop in RMR is attributable to reduced body size versus adaptation. State what additional information you'd need to do this properly rather than approximately.

B7. A person reports eating 1,200 kcal/day and gaining weight. Using §5.11, list what you'd ask and what would move this from "probably a measurement issue" to "needs a physician this week."

B8. Explain why a $180 metabolic test at a gym improves the more accurate half of a two-part estimate. What is the less accurate half, and why can't the test fix it?

Part C — Skills & Practice ⭐⭐–⭐⭐⭐

C1. Calculate your own, by hand. The Project Checkpoint. Write out every line of the arithmetic on paper — do not use a website. Then compute your ±10% range and your TDEE range. Write down all six numbers.

C2. Compare to your diary. Put your Chapter 4 diary total next to your TDEE estimate. Is the difference between them larger or smaller than your error bar? Answer honestly, and note what follows if it's smaller.

C3. Run the two-week protocol. Eat at approximately your estimate for two to three weeks. Track your weekly average weight. At the end, calculate what your TDEE actually appears to be, based on what happened. Compare to the equation. (This is the only exercise in this chapter that produces a real number rather than an estimate.)

C4. The percentage-to-calories drill. Find five supplement or product claims that state an effect as a percentage — of metabolism, of fat oxidation, of energy expenditure. Convert each to calories per day for a realistic person. Then compare each to one ordinary food item. Write the comparison as a single sentence you could say out loud.

C5. Audit an online calculator. Use three different online TDEE calculators with identical inputs. Record the three answers. How far apart are they? Do any of them display an error bar or a confidence range? What does the presentation imply about the precision, and is that implication honest?

C6. Build the differential. For each of the six symptoms below, name at least one condition from §5.11 it might point to, and what test would investigate it: cold intolerance and hair thinning · irregular periods and acne · rapid 4 kg gain over five days with ankle swelling · loud snoring and daytime sleepiness · purple abdominal striae and easy bruising · weight gain starting three weeks after a new prescription.

Part D — Synthesis & Critical Thinking ⭐⭐⭐

D1. The chapter argues that "my metabolism is broken" is usually a measurement or expectation problem, and that reflexively assuming so will eventually cause a clinician to miss a real illness. How should a practitioner hold both? Design a decision rule.

D2. The weight-loss competition follow-up study is small, uncontrolled, and studies an extreme intervention. It is also the most-cited evidence for persistent metabolic adaptation. Is citing it responsible? What would responsible citation look like — and how would you phrase it to a patient rather than a colleague?

D3. If NEAT is the largest modifiable component of TDEE and it is largely unconscious, what follows for intervention design? Can you deliberately increase an unconscious behavior? What would that even look like?

D4. The chapter says genetic variation in RMR is real (~±10%) and "not the explanation for a 1,000-calorie discrepancy." Someone objects: isn't this just a more polite way of telling people they're wrong about what they eat? Answer the objection honestly.

D5. Consider the ethics of selling metabolic testing to the general public. The measurement is real. The information is genuine. Its practical value over a free two-week trial is close to zero. Is selling it deceptive? Where's the line between a legitimate service and precision theatre?

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

M1. (With Chapter 4.) Combine the §4.7 measurement error on intake with the §5.3 error bar on expenditure. For a person estimating a 400 kcal deficit, what is the realistic range of their true energy balance? Could they in fact be in surplus?

M2. (With Chapter 4.) Chapter 4's thermostat analogy and Chapter 5's adaptation section describe the same phenomenon at different levels. Map the components of adaptation (RMR drop, NEAT drop, efficiency, appetite) onto the parts of the thermostat.

M3. (With Chapter 3.) Why does the respiratory quotient of a resting human sitting at ~0.8 matter for Chapter 3's account of what happens to absorbed nutrients? What does it tell you before you've read Chapter 6?

M4. (With Chapter 2.) Run the "each pound of muscle burns 50 calories" claim through the Claim Filter. Pay particular attention to question 1 — where does this claim's evidence sit on the ladder, and can you find any?

M5. (With Chapters 1 and 2.) The "metabolism boosting" supplement category persists despite effects of a few tens of calories. Use Chapter 1's myth shapes and Chapter 1 §1.5's incentive analysis to explain the persistence.

M6. (Revisit at Chapter 24.) Predict now: what proportion of people who lose 10% of body weight maintain that loss at five years? Write your guess. Chapter 24 gives the evidence.

Part E — Research & Extension ⭐⭐⭐⭐

E1. Find the original organ-level metabolic rate data (search for work on organ-tissue energy expenditure, often associated with Elia's analyses). How were these figures derived, and what are their limitations? Then consider how confidently the ~13 kcal/kg/day muscle figure should be stated.

E2. Locate research on age-related changes in total energy expenditure measured by doubly labelled water across the lifespan. When does expenditure actually decline, adjusted for body composition? Compare that to the popular belief about metabolism in your thirties, and to what this chapter says.

E3. Read the weight-loss competition follow-up study and at least two published critiques of it. Then find data on metabolic adaptation in people who lost weight through more moderate means. Write a page reconciling them — and note where you had to leave the question open.

E4. Investigate brown adipose tissue in adult humans: how was its presence confirmed, how much energy can it plausibly account for, and what happened to the wave of commercial interest that followed the discovery? This is a good case study in a genuine scientific finding being immediately over-monetized.