I fail to see the causal link you're proposing. Where is the evidence that masks have had an effect on preventing cases?

On the other hand, we have good evidence[1] that obesity levels have a huge impact on cases:

> Professor Rachel Batterham, Royal College of Physicians' lead adviser on obesity, said:

> “The link between high levels of obesity and deaths from COVID-19 in the UK is indisputable, as is the urgent need to address the factors that lead so many people to be living with obesity.

> “With 30% of COVID-19 hospitalisations in the UK directly attributed to overweight and obesity, and three quarters of all critically ill patients having overweight or obesity, the human and financial costs are high.

From just the opening page of the report[2] itself:

> We show that in those countries where overweight affects only a minority of the adult population, the rates of death from COVID-19 are typically less than one tenth the levels found in countries where overweight affects the majority of adults.

> We also show that the drivers of overweight – especially high levels of consumption of processed foods – are associated with mortality from COVID-19.

From the report's country profiles:

Adult overweight BMI >25kg/m2 (2016)
US : 67.9
UK : 63.7
Japan : 27.2

Adult obesity BMI >30kg/m2 (2016)
US : 36.2
UK : 27.8
Japan : 4.3

Insufficient physical activity % adults (2016)
US : 40.0
UK : 35.9
Japan : 35.5

Pulses per capita kg/pa (2014-2017)
US : 3.6
UK : 3.7
Japan : 1.5

Root vegetables per capita kg/pa (2014-2017)
US : 55.5
UK : 88.5
Japan : 24.9

Vegetable oil per capita kg/pa (2014-2017)
US : 19.5
UK : 13.1
Japan : 15.5

Animal fat per capita kg/pa (2014-2017)
US : 3.3
UK : 5.6
Japan : 1.0

Sugar per capita kg/pa (2014-2017)
US : 66.2
UK : 37.8
Japan : 26.9

Sugar energy per capita kcal/pd (2014-2017)
US : 607
UK : 342
Japan : 252

Sugar-sweetened beverage per capita l/pa (2015)
US : 236.6
UK : 124.0
Japan : 144.3

There is much more in that report, it's well worth a read.

This CDC report[3] states:

> Among 4,899,447 hospitalized adults in PHD-SR, 540,667 (11.0%) were patients with COVID-19, of whom 94.9% had at least 1 underlying medical condition

> Certain underlying conditions and the number of conditions were associated with severe COVID-19 illness. Hypertension and disorders of lipid metabolism were the most frequent, whereas obesity, diabetes with complication, and anxiety disorders were the strongest risk factors for severe COVID-19 illness.

Cases are most frequently discovered due to severity of symptoms as being symptomatic will lead to testing. Thus the link between confirmed cases and underlying health conditions is easy to see. It goes on to state:

> The analysis also shows that the total number of underlying conditions is strongly associated with severe COVID-19 illness.

> The percentage of the US adult population known to have 2 or more underlying medical conditions ranges from approximately 38% to 64% by state (12). Previous studies demonstrated that patients with medically attended COVID-19 often had multiple underlying medical conditions (6). However, studies have rarely focused on the effect of the number of conditions on severe COVID-19 illness. We found that the risk of death, IMV, and ICU admission was often incrementally higher with a higher number of underlying medical conditions. Our finding that the number of underlying medical conditions is itself a risk factor for severe disease from COVID-19 identifies a population that has not been clearly described in previous literature.

As I pointed out in another comment, the lack of testing in Japan keeps its number of confirmed cases low (which has seemed convenient given the government's clear desire for the Olympics to proceed), but the country is experiencing a huge uptick in cases right now - is this because of people suddenly dispensing with masks? I haven't noticed it, it's close to 100% compliance among adults even outdoors. Is there anything on this graph[4] to suggest that masks have efficacy at all? Why do randomised controlled trials repeatedly fail to show a positive effect?

As to population density, Japan is only 41st on this list[5]. If being packed into a train is the problem then why the uptick now and not before? There's no lockdowns here and working from home is still not the norm. Did masks slow down the spread just until this point yet could not be held back any longer?

So I say again, where is the evidence like this for masks? There is none.

[1] https://www.rcplondon.ac.uk/news/rcp-responds-world-obesity-...

[2] https://www.worldobesityday.org/assets/downloads/COVID-19-an...

[3] https://www.cdc.gov/pcd/issues/2021/21_0123.htm

[4] https://ourworldindata.org/explorers/coronavirus-data-explor...

[5] https://en.wikipedia.org/wiki/List_of_countries_and_territor...