Week 1: Why the Advice Doesn't Fit

22 February 202712 min read

Course premise#

Public guidance is the best summary we have of what helps people in general. Sleep seven to nine hours (Hirshkowitz et al., 2015). Aim for seven thousand steps or more (a companion statement to the 24-Hour Movement Guidelines). Enjoy a healthy breakfast (a practical tip in the Australian Dietary Guidelines summary booklet, not one of the five guidelines themselves). Notice that these are ranges and aims rather than instructions, and that none of them knows anything about you. This course teaches you to close that gap in three moves. Realisation: read the guidance accurately, then look at your own day and find where you actually sit in it. Change: alter one thing, using the guidance for what to change and how, which later lectures cover in detail. Rethinking: read what comes back from your body, your mood and what you actually did, and revise the change against it. Then go round again, because you will not be the same person in May that you were in March. The unit is a single day: twenty-four hours observed, adjusted, and observed again. What the course will not do is hand you a finished answer, because a finished answer belongs to one person across one stretch of days, and it is no substitute for a doctor. What it gives you instead is the loop itself, and the judgement to know when a result is worth acting on.

Find the guidelines that suit you#

Guidance is not one rule for everyone, and the three things it narrows on are not this course’s invention. Explaining how much sun a person needs, ARPANSA writes that vitamin D from sunlight “depends on many factors including location, time of year, day-to-day activities and individual circumstances”: who you are, where you are and when it is, in one sentence from the national radiation authority. What differs is how openly each one is used. Guidance is organised by who you are, settles where you are before you read a word of it, and often leaves when it is for you to work out.

Who you are#

This is the axis guidance is built on, to the point of being its table of contents. Australia’s 24-hour movement guidelines are published as a menu of people under the heading “Find the guidelines that apply to you”: birth to five, five to seventeen, eighteen to sixty-four, pregnancy, sixty-five and over, and people with disability. The sleep panel splits the same way, seven to nine hours for adults and seven to eight for older adults, so a figure quoted without an age band is already missing a caveat. The UK vitamin D advice narrows again inside the country, recommending supplements all year rather than only in winter for people who are rarely outdoors, who cover most of their skin, or who have dark skin from Black African, Black Caribbean or South Asian backgrounds, because melanin absorbs the UV that makes vitamin D. Read the caveats before the number: they are the part where guidance tells you whether it is talking to you at all.

Where you are#

Place is usually settled before you read anything, because a guideline is written for a country, which is also why the same rule gives different instructions at different latitudes. Australia’s sun rule is a single number: protect yourself whenever the UV index reaches 3, and below 3 do not, so your skin can make vitamin D. One threshold, over a country spanning more than thirty degrees of latitude, which means the rule is on all twelve months of the year in Darwin, ten in Sydney and eight in Hobart. Only the more careful guidance divides this up inside the country: Cancer Council notes that northern areas need protection all year, while in some southern areas “there are times of the year when sun protection may not be necessary”. In the United Kingdom the shortfall runs the other way, and everyone over four is advised to consider ten micrograms of vitamin D daily from October to March, because there is not enough sun in those months to make it. Same sentence, and the instruction inverts.

Two things the table cannot tell you, and both matter before you lean on any single number in it. The grid is 1.5 degrees, roughly 165 kilometres, so each value describes the region around a city rather than the city itself. And Australia’s advice keys off the forecast for the day, while these are monthly averages under cloud-free skies, so a month averaging just under 3 still contains days well above it. What the table shows is when the threshold is typically crossed, not what any particular Tuesday will do.

That is also why the two rows at 35 degrees south are worth reading carefully rather than triumphantly. Adelaide averages 2.98 in May and Canberra 3.04, so the rule reads as off in one and on in the other on a difference of six hundredths of an index point, and the grid places both in the same latitude band. A gap that small sits well inside what a 1.5 degree monthly average can actually resolve, so the honest lesson is not about Adelaide or Canberra. It is that a threshold laid across a smooth gradient will always manufacture pairs like this, and that is true of every cut-off this course will show you.

When it is#

Time is the axis guidance most often leaves implicit. Australia’s rule is written as a condition rather than a season, sun protection whenever the index reaches 3, so the calendar is a consequence you are left to work out. Below is that work done for two cities. Hobart’s average noon index is under 3 from May to August and Melbourne’s from May to July, the months when sun protection is not recommended at all, so the same person in the same city is told to cover up in January and to get some sun in July, for the same reason both times. The UK advice does the opposite and names its months outright, October to March. Neither instruction is a revision of the other; the number moved and the rule did not. A recommendation with no season attached is incomplete, and the ones worth trusting say when they apply.

Australia is not the only country keying its sun advice to that number. ARPANSA recommends sunscreen on days when the UV index is forecast to reach 3 or above, the Centers for Disease Control and Prevention says to protect your skin when the index is 3 or higher in your area, and Health Canada says the same at 3 or higher. Read quickly, that is three countries converging on one threshold, which would make the threshold more trustworthy than any single country’s version of it. Read slowly, it may be one number quoted three times: the Global Solar UV Index, developed by the World Health Organization with the World Meteorological Organization, the United Nations Environment Programme and the International Commission on Non-Ionizing Radiation Protection, already states that below an index of 3 no protective measures are needed and that above the threshold value of 3 protection is necessary. None of the three national pages says where its number came from, so all you can honestly conclude is that the agreement has not been shown to be independent, which is weaker than it first looked and more useful to know.

The narrowing runs out before it reaches you. A category like “dark skin from South Asian backgrounds” covers enormous variation in skin, in where people live, in time spent outdoors. It is a better guess than no guess, and it is still a guess about a group. Guidance narrows from everyone to a group you belong to, and good guidance says so plainly. The last step of this course is that same move, carried to the only group with no variation left inside it.

We are in Australia, so three national documents are the place to start: the Australian Dietary Guidelines, the 24-hour movement guidelines, and the guidelines NHMRC publishes across everything else it covers. Each states who it is written for and what evidence it rests on, which is the part to read before the numbers. The map below carries that closing move outward, and asks what the equivalents are in ten other countries and what shape they arrive in.

What the mark records is the shape of the document rather than what is inside it. Canada’s guideline for children and youth was, on its own account, the first evidence-based guidelines to address the whole day, putting activity, sitting and sleep in one place instead of three. Australia did not repeat that work: its own development report says the benefit was that it could leverage the considerable work done in Canada, finishing in far less time and with fewer resources, which is a health department telling you plainly that it copied, and a good decision. Within these eleven, that is the whole of the twenty four hour format’s reach: the country that invented it, one that took it outright, and one that took it for children only.

Seven of the eleven stop at bedtime. The United Kingdom, the United States, Germany, France, the Netherlands, Korea and China all publish movement guidance that sets a target for activity and a target for sitting and none at all for sleep. Germany’s recommendations name the four things they are about, type, duration, intensity and volume of physical activity, and sleep is not among them; where sleep does turn up it is in the chapter on older adults, as something training can favourably influence. Korea’s guide asks at every life stage that the time spent sitting during the day be kept to a minimum, and sets no sleep target at any of them. That is the majority position in this reading, and the integrated format is the exception rather than the direction of travel.

Japan is where a third box stopped being enough. Its movement guide defines its own sedentary target as all waking activities performed sitting or lying down, so read on that document alone Japan belongs beside the United Kingdom. Two months later the same ministry published a sleep guide that sets recommendations for adults, for children and for older adults, and opens by calling sleep an essential restorative activity across all age groups. Sleep in Japan is a national target with a twenty year lineage behind it. It is simply not in the same document, and filing that under the waking hours only would have said the opposite of what is true.

New Zealand had already broken the scheme once from the other direction. Its guideline for five to seventeen year olds is Canada’s, adapted with permission and retitled Sit Less, Move More, Sleep Well, so children there are handed a whole day. Its adults get eating and activity bound into a single document whose five activity statements set no sleep target anywhere in them. France publishes one instrument covering diet, physical activity and sitting together, and China’s dietary guideline carries a sitting target of its own under a principle called balance eating and moving. So joining what you eat to how you move is live in three of the eleven, and joining the waking hours to the sleeping ones is live in three others, and they are not the same three.

Who is allowed to publish matters as much as what gets published, and the eleven do not agree about that either. Australia’s guidelines come from a government department and from NHMRC, a body that develops guidelines for clinical practice, public health, environmental health and ethics. Canada’s 24-hour guideline comes from a professional society. France names four bodies in one sentence, two that supplied the science, one that commissioned the update and one that wrote it. Only the United Kingdom, with NICE, and the Netherlands, with a council that describes itself as an independent scientific advisory body to government and parliament, have anything sitting cleanly where NHMRC sits, and the other eight entries say so rather than naming a near miss.

Six of the eleven publish in a language this course does not read, so each of their entries carries the publisher’s own sentence and an English rendering beside it, labelled with where the English came from. Japan’s ministry issues English editions of both its guides, the journal carrying China’s guideline prints an English abstract, and the Dutch health council publishes an English site, and those are quoted as their publishers wrote them. The German, French, Korean and two of the Chinese renderings are this course’s and nobody else’s, which is a weaker thing and is labelled as one. The Netherlands is where that mattered: its Dutch page asks the minister to get people moving more and sitting still less, and the council’s own English page renders the same sentence with only the moving half in it.

Eleven countries is not a sample of the world and cannot support a claim about one. They were picked because their guidance is published, findable and either written in English or accompanied by an English edition somebody official issued, which selects on wealth and on administrative habit before it selects on anything else. What the eleven can support is narrower and still worth having. The twenty four hour format exists, it is a minority arrangement even among countries that publish this kind of guidance at all, and a reader who assumed their own country’s format was the international standard now has eleven documents to check that against.