Chapter 4 — Exercises

The arithmetic here is easy. Holding both halves of the threshold concept at once is not.

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

Selected answers in Appendix J. Calculation tools in Appendix B.

Part A — Conceptual Understanding ⭐

A1. What is a calorie, physically? What is the difference between a calorie and a kilocalorie, and which one is on the label?

A2. State both halves of this chapter's threshold concept in your own words. Explain why holding only one half leads to a specific error, and name the error for each half.

A3. Name the four components of energy expenditure with their approximate shares of the total.

A4. What is NEAT? Why is its variability significant, and why does the word "unconscious" matter so much?

A5. Give the approximate thermic effect of food for protein, carbohydrate, and fat. Then state honestly how much this matters for a whole diet.

A6. List three ways the two sides of the energy balance equation are coupled. Why would a body evolve to work this way?

A7. What is doubly labelled water, and what does it consistently reveal when compared with self-reported intake?

A8. Why is each gram of glycogen accompanied by roughly three grams of water, and what does that explain about early weight loss on a low-carbohydrate diet?

A9. Explain why 100 kcal/day matters more than a single 1,200 kcal meal. Show the arithmetic for both.

A10. Where, physically, does fat go when a person loses it?

Part B — Applied Analysis ⭐⭐

B1. Theo's intake was 3,160 kcal/day against needs of about 2,670. Calculate his daily surplus, his annual surplus, and — using the rough 3,500 kcal/lb figure — the naive predicted annual weight gain. Then explain, using §4.6, why his actual gain has been slower than that.

B2. A friend says: "I've been eating 1,200 calories a day for three months and haven't lost a pound. My metabolism must be destroyed." Write the response you'd actually give. It must be honest, must not accuse them of lying, and must include a circumstance under which they should see a doctor.

B3. A product claims celery is a "negative calorie food" — digesting it burns more energy than it contains. Evaluate. What would have to be true, and what is the actual thermic effect of a carbohydrate-and-fiber food?

B4. Someone loses 6 lb in the first five days of a low-carbohydrate diet, then loses nothing for the next two weeks and concludes the diet stopped working. Explain what actually happened in both periods.

B5. A wearable reports that a 45-minute run burned 620 calories. List four separate reasons that number should not be treated as accurate, and say in which direction the error most commonly runs.

B6. Two people both maintain weight at "2,000 calories." One has a desk job and runs three times a week; the other is a restaurant server on their feet nine hours a day and never exercises. Using §4.5, explain how both can be true, and say which component differs most.

B7. Explain why the Hall ultra-processed food crossover trial is a problem for a strict "just eat less" framing — and then state what it does not show.

B8. A person tracks meticulously and eats "1,650 kcal/day" but isn't losing weight. Using §4.7, estimate the plausible range of their true intake and their true expenditure. Do the ranges overlap? What does that imply about the usefulness of the number?

Part C — Skills & Practice ⭐⭐–⭐⭐⭐

C1. Do the food diary. The Project Checkpoint. Three days, two weekdays and one weekend day, recorded in the moment. This is the single most informative exercise in Part I and the one most readers skip. (Non-tracking alternative in the chapter and in Appendix F.)

C2. Measure one portion. Pick one staple you eat frequently — rice, pasta, cereal, oil, nut butter, cheese. Serve yourself the amount you'd normally have. Then weigh it and compare to the package's stated serving. Record the ratio. Theo's rice was 2.4×. Most people's is between 1.5× and 3×, and almost nobody's is 1.0×.

C3. Find your invisible calories. For one day, write down everything you consume that you would not have listed if asked "what did you eat today?" Drinks with calories. Coffee additions. Cooking oil. Tastes while cooking. Other people's leftovers. Anything from a communal container. Total it.

C4. The seven-day average. If you weigh yourself, record daily weight for one week at the same time under the same conditions. Note the range from lowest to highest. Then calculate the average. Compare the size of the daily fluctuation to the amount of fat you could plausibly have gained or lost in a week. (If weighing is distressing for you, skip this and read §4.9 instead — the conclusion is "weigh less or not at all," and you can arrive at it without the demonstration.)

C5. Deconstruct a "fat burning" claim. Find a product or protocol claiming to boost metabolism or burn fat. Identify: which component of §4.5 does it claim to affect? By how much, in calories? Is that number ever stated? What would that number have to be to matter?

C6. The intervention design exercise. Take Theo's seven sources of surplus from the chapter opening. Design a three-change intervention for him. For each change, estimate the calories saved and rate — honestly — the probability he'll still be doing it in six months. Multiply. Compare your total to a hypothetical "eat 1,800 calories a day" plan scored the same way.

C7. Rewrite the advice. Take the sentence "eat less, move more." Rewrite it as advice that actually contains information — specific enough that a person could act on it tomorrow. Notice how long it gets, and how much it depends on knowing things about the person.

Part D — Synthesis & Critical Thinking ⭐⭐⭐

D1. The chapter argues that "calories vs. hormones" is a category error. Defend that position. Then argue against it: is there a version of the hormonal argument that isn't just energy balance in different clothes?

D2. §4.6 says the regulatory system defending body weight is "performing exactly the function it was selected for." Does an evolutionary explanation of a phenomenon tell you anything about what to do about it? Consider carefully — this reasoning is used constantly in nutrition and is often invalid.

D3. If self-reported intake is routinely ~20% or more below true intake, and energy expenditure equations are ±10% at best, is calorie counting defensible as a clinical tool at all? Argue both sides. Then say what you'd actually do with a patient.

D4. The chapter says exercise contributes a smaller share of expenditure than people expect, and also that exercise is extraordinarily good for you. Reconcile these. Then explain why the framing "exercise to burn calories" might be actively counterproductive — for adherence, for enjoyment, and for how people relate to food.

D5. Consider the "cheat meal" concept. The chapter argues it does damage in both directions. Construct the strongest defense of the concept — there is one — and then say whether it survives.

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

M1. (With Chapter 3.) Name three mechanisms from Chapter 3 that explain why the same number of calories produces different amounts of hunger. Then explain why this makes "a calorie is a calorie" a 🟡 rather than a ❌.

M2. (With Chapter 2.) The Hall ultra-processed food trial appears twice in this chapter. Place it on the evidence ladder, name two limitations, and say what a stronger version of that study would look like — and why it hasn't been run.

M3. (With Chapter 2.) "People who track their food lose more weight." Run this through the Claim Filter. Pay particular attention to questions 3 and 4.

M4. (With Chapters 1 and 3.) Theo's ten-day juice cleanse (Chapter 3, Case Study 1) produced rapid weight loss that came back within three weeks. Using §4.9, explain the rapid loss and the rapid return. Then use Chapter 1's incentive analysis to explain why the product is sold on the first and silent about the second.

M5. (With Chapter 2.) Someone cites a study showing a high-protein diet produced greater fat loss than an isocaloric lower-protein diet. Before accepting the "protein is metabolically superior" conclusion, name three mechanisms from this chapter and Chapter 3 that could explain the result without any metabolic advantage at all.

M6. (Revisit at Chapter 24.) Write down, now, what you think the main reason is that most people regain lost weight. Seal it. Chapter 24 gives the evidence-based answer, and comparing them is a good test of whether §4.6 landed.

Part E — Research & Extension ⭐⭐⭐⭐

E1. Read about the Minnesota Starvation Experiment (Ancel Keys and colleagues, 1940s). What happened to the participants' metabolic rate, their NEAT, their psychology, and their eating behavior during semi-starvation and refeeding? Then consider what it implies about modern aggressive-deficit dieting — and note the ethical impossibility of ever repeating it.

E2. Find published research using doubly labelled water to validate self-reported dietary intake. How large is the discrepancy, and how does it vary by body weight, sex, and study setting? Then consider what this does to the interpretation of every observational nutrition study you read in Chapter 2.

E3. Investigate the "constrained total energy expenditure" hypothesis — the proposal, based on work in populations with very different activity levels including the Hadza, that total daily energy expenditure is less responsive to physical activity than the additive model predicts. What's the evidence? What would it mean for exercise-based weight loss advice if it's right? (This is genuinely unsettled science and a good exercise in holding an open question open.)

E4. Look up the follow-up research on contestants from a televised weight-loss competition, examining resting metabolic rate years after the show. What was found, how has it been reported, and — critically — what are the study's limitations as a basis for general claims about metabolic damage? This is a case where a real finding has been substantially over-generalized in both directions. (Chapter 5 discusses it; forming your own view first is more valuable.)