The UK government has published its impact report for the three-tier COVID-19 alert system, which will be introduced in England tomorrow (2 December), when the one-month long national lockdown comes to an end.

Called Analysis of the health, economic and social effects of COVID-19 and the approach to tiering, the 48-page report lays out the economic and health impacts that the government says have guided it, when determining the specific measures for each tier.

In the report, the government outlines how there is a "bigger picture" to be considered when it comes to the pandemic's impact on public health – as well as the virus' direct impact on people's health.

"From the outset of the pandemic, the government has been aware of the importance of a wide range of societal health impacts, in terms of deaths and morbidity, associated with the COVID-19 situation," the report reads.

One of these detailed in the report is the fall in physical activity levels.

"There was a 7.1 per cent decrease in ‘active’ adults from mid-March to mid-May 2020 compared to the same period in 2019," the report reveals.

"This improved subsequently, particularly when people have been able to access gyms and group exercise."

The report reveals that this – the fear that physical activity levels would fall further during the tiered approach – has featured heavily in the government's thinking behind excluding gyms and physical activity facilities from any baseline measures of the three tiers. The government has already confirmed that gyms, health clubs and leisure centres would be able to open their doors – and keep them open – under all three tiers.

"We anticipate that physical activity will be slightly lower under the tiers than has historically been the case," the report reads.

"To mitigate this, enabling exercise and keeping gyms open has been prioritised in all tiers."

In the report, the government also accepts that the new, more stricter tiered system could have a negative impact on people's mental health – but that doing nothing and letting the virus "spread unchecked" would be "even worse" for mental health outcomes.

"There are likely to be some short-term negative mental health impacts associated with restrictions under the tier system," the report reads.

"However, it is important to recognise that mental health could be worse in a counterfactual situation of COVID-19 resuming exponential growth, an increase in deaths and major disruption to health and care services.

"The higher the tier, the greater the likely impact on isolation, although care and support bubbles provide some mitigation. It is understood that the need for social interaction may be greater during periods of adversity."

• To read the full impact report, click here.