Week 4 Lecture: Sleep, Health, and Exercise

How much sleep you actually need, the plate-level version of nutrition, and why more exercise isn't always better

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Introduction#

Monday: plan says asleep by 11:30pm, actual is still awake at 3am finishing an assignment. Tuesday: “will sleep early tonight,” typed into a note never looked at again. Sleep, food, and exercise are the three areas of life most often optimised in intention, never in practice — today’s scope is sleep duration, exercise frequency, and nutrition at the plate level (what actually counts as a balanced meal), plus the fridge from Week 2, revisited; detailed nutrition science (macronutrient targets, calorie counts) stays out of scope.

Definitions#

Bedtime (noun)

a specific, named clock time at which one intends to be asleep, not merely "later."

Balanced meal (noun)

a plate containing more than one food group, particularly one that is not currently instant noodles.

Exercise (noun)

physical activity undertaken on a stated schedule, distinguished from "the walk to the vending machine."

Body#

• How much sleep you actually need, and how to get there. Hirshkowitz, M., Whiton, K., Albert, S. M., et al. (2015) recommend seven to nine hours for adults 18–64 — a real range, not a rough guess. Two things get you there: a wake time fixed to the same clock time every day, weekends included, and a screen wind-down that starts at a named time before bed, not “whenever I feel tired.”

Check-in: Who got seven hours or more last night? Keep your hand up if you also got it the night before.

• Jordan’s Week, fully unpacked. Monday: asleep-by-11:30 plan, awake at 3am finishing an assignment — the 7am gym slot goes the same way, four snoozes then skipped entirely. Tuesday: “will sleep early tonight,” written down and never reopened; 2am arrives via one more episode, and the run logged in the plan was a walk to the vending machine and back, twice. Wednesday: breakfast skipped, the same bowl of instant noodles twice in one day, reported to a friend, straight- faced, as “I’ve been so good with food lately.” Thursday: bed on time for once, then up at 4am for a single phone notification. Friday: no plan was written at all. Saturday: sleep until 2pm to “catch up,” followed by lying awake until 4am that night. Sunday: next week’s plan, copied from this one, unchanged. Six stated intentions, zero actual times — the week’s own Lab breaks down exactly where each plan met reality.

Check-in: Name one day in Jordan's Week where the stated plan and the actual outcome have nothing in common.

• Exercise as a frequency, not a location. Chekroud, S. R., Gueorguieva, R., Zheutlin, A. B., Paulus, M., Krumholz, H. M., Krystal, J. H., & Chekroud, A. M. (2018) found exercisers reported 1.49 fewer poor-mental-health days per month than non-exercisers, peaking around 45 minutes 3–5 times a week — but more than 3 hours a day was associated with worse outcomes than none at all. A beginner routine that hits that range: three sessions a week, 20–30 minutes each, at a stated time slot — any activity that raises your heart rate counts, and a gym session is one option, not the only one; a brisk walk on a fixed route satisfies the same frequency.

Check-in: According to this study, is more exercise always better? What does the data actually say?

• The fridge, revisited. Week 2’s fridge shelf hasn’t changed: condiments, one ageing lime, still nothing that constitutes a meal — which is exactly why Wednesday’s plan in Jordan’s Week collapses into the same bowl of instant noodles twice in a day. A sleep schedule and an exercise plan both assume there’s something to eat between them; an empty fridge breaks both.

Check-in: What's the direct link between an empty fridge and Wednesday's two servings of instant noodles?

• Nutrition, at the plate level: how to actually build a balanced meal. Three items on the plate, at the same sitting, not spread across the day: a base (rice, pasta, bread), a protein (eggs, canned beans, last night’s leftover chicken), and something that isn’t beige (a vegetable — any vegetable, frozen counts). A piece of fruit eaten four hours after the noodles doesn’t retroactively balance the noodles. The only way the fridge from Week 2 supplies all three on a Wednesday is if it was stocked on the weekend before — checking for the first time on Wednesday night is checking too late.

Check-in: Look at what you actually ate at your last sitting — name the one food group missing from the plate.

In-lecture activity#

Conclusion#

A plan has a time; an intention doesn’t. More isn’t always better. This is the topic most students believe they’re managing and visibly aren’t — you now have the real recommended range, a fixed wake time and wind-down to get there, a beginner exercise routine that isn’t tied to any one location, the fridge as a reminder that a schedule needs something to actually run on, and the three-item test for whether what’s on the plate actually counts as a meal. Coming up: this week’s lab (the sleep-and-exercise plan), and Assignment 1 (Makeover) due this Friday at 12:00.

This week’s reflection, due 12:00 Tuesday of week 5: describe a night your sleep schedule held, or didn’t, and name the one factor that decided which.