Discussion Guide — Chapter 7

1. "Same blood glucose, more insulin. What could account for that?"

Open with the experiment, before any content. Listen for: students generating hypotheses — the mouth, the stomach, the gut, a nerve. Let several run before revealing. The point is that the answer is not obvious, and that a genuinely surprising experimental result is what created an entire field.

2. "The nausea and the weight loss come from the same action. Does that change how you think about the side effect?"

Listen for: the reframe from "unfortunate side effect" to "the mechanism, overshooting." Then the clinical follow-up: how would you explain this to a patient who is considering stopping because of nausea? (Answer available in the chapter: it typically attenuates while the metabolic effects persist, because tolerance is a property of drug-tissue pairs.) Students who can deliver that explanation have learned something usable.

3. "GIP is blunted in diabetes, promotes fat storage, and adding it helps anyway. What is going on?"

The best discussion in the chapter, precisely because there is no answer. Listen for: students generating the four explanations independently, and for someone noticing that the desensitization possibility means an agonist could act like an antagonist. Do not resolve it. Point out that both GIP agonists and antagonists are in development, and ask what it means for a field to be running both.

4. "Is the drug the same signal as the hormone?"

Listen for: students assembling the argument from the three-routes diagram. Then push: what would have to be true for "restores natural signaling" to be an accurate description? (A demonstrated prior deficiency, restoration to a normal range rather than exceeding it, and the same routes at the same times.) None holds. This is the section where a marketing sentence becomes visibly false rather than merely loose.

5. "Bariatric surgery was assumed to work by restriction for decades. What broke that model?"

Listen for: the observation that glucose improved before weight did. Then the meta-point: the useful result is almost always the one that does not fit. Connect to Chapter 3's Pavlov coda and Chapter 5's CAST. Ask what would have to happen for someone to notice such an anomaly rather than attributing it to noise.

6. "Does the incretin system explain obesity?"

Close here. Listen for: students reaching "no, and a drug working on a system is not evidence the system caused the disease." Then the harder question: what would count as evidence that it did? Students will find this difficult, which is the point — the question of what causes obesity is not answered by any drug's success, and Chapter 12's debate is much better if they have already noticed that.