Some 90% of British households increased their calorie intake during the pandemic as they more than offset a drop in restaurant meals with takeaways and larger supermarket shops, a study suggests.

The pandemic led to a large and sustained increase in the intake of calories, which peaked at over 15% above the normal level around May, towards the end of the UK’s first national lockdown, and remained around 10% above normal at the end of 2020, according to the Institute for Fiscal Studies (IFS).

Using data on millions of food and non-alcoholic drink purchases from stores, takeaways and restaurants, the study found that the pandemic led to calories from restaurant meals falling to zero during the UK’s first national lockdown, before recovering somewhat over the summer and declining again as restrictions in the hospitality sector were reintroduced in the autumn.

Increases in food consumed at home more than offset drops in calories from eating out. 90% of households increased their calorie intake, with the largest rises for the wealthiest households.

However this was more than offset by a large increase in calories from takeaways, which peaked at more than double the usual levels in the UK’s second national lockdown in November 2020.

Calories purchased from supermarkets and grocery stores were also more than 10% above normal levels throughout the pandemic.

Overall, people increased their calories from raw ingredients by more than those from ready-to-eat meals and snacks and treats, with the pandemic leading to a shift in the balance of calories towards foods that required home preparation.

The report said the most plausible explanation for the sustained increase over the pandemic was higher consumption rather than changes in household composition, food waste or stocking up.

While the majority of households increased their calorie intake, those higher up the socio-economic ladder exhibited the largest increase and retired households the smallest increase.

Households living in London and those with a relatively young working-age head of the household also had larger increases in calories, associated with a higher probability of working from home, which pointed towards changes in working patterns being a factor in more calorific diets, the report said.

The IFS said its findings suggested that the pandemic and the associated changes in people’s lifestyles had exacerbated the challenges of improving the population’s diet and reducing obesity levels.

IFS associate director and an author of the research, Kate Smith, said: “The huge changes in where people work, eat and socialise over the past year have led to a significant rise in calorie intake.

“Increases in food consumed at home more than offset drops in calories from eating out. 90% of households increased their calorie intake, with the largest rises for the wealthiest households.”

Martin O’Connell, deputy research director at IFS and co-author of the research, said: “An important question for policymakers is whether higher calorie consumption persists as we emerge from the pandemic.

“Our findings point towards increased home working as a factor in driving higher calorie consumption.

“This could exacerbate the challenge of improving population diet and reducing obesity levels.”

Mark Franks, director of welfare at the Nuffield Foundation, one of the funders of the research, said: “We know that the pandemic has had major impacts on both physical and mental health, spread unequally across society.

“Through important new analysis of changes to people’s diets, this report adds to that evidence base.

“The rise in calorie consumption reinforces the need to address some of the systemic issues behind food inequality, such as the cost of a healthy diet relative to a less healthy one, that can also contribute to obesity.

“It also should not distract from the significant minority who have struggled to access food throughout the pandemic, as evidenced by increased use of food banks and concerns over lack of access to free school meals.”