The British public has been under-reporting its daily calorie consumption, potentially misleading policymakers to focus on wrong strategies – such as increasing physical activity levels – when attempting to tackle the obesity epidemic.

The claim is made in a paper published today by the influential Behavioural Insights Team (BIT).

In its Counting Calories: How under-reporting can explain the apparent fall in calorie intake report, BIT points to scientific and economic data which shows the average daily intake to be at 3,000 calories per person – rather than the 2,000 cited in official surveys.

According to BIT, the discrepancy could explain rising obesity levels, despite decades of surveys showing people to be eating less – and could mean that focus should be switched from increasing people’s activity levels to reducing their calorie intake.

The report suggest there are three main reasons people are not accurately reporting what they eat – the difficulty of tracking snacks, “dishonesty” by those desiring to lose weight and fewer people overall taking part in the surveys.

“Several recent reports have noted that official statistics show a large decline in calorie consumption during the last forty years – the same period that obesity rates have gone up,” says Michael Hallsworth, BIT’s director of health and tax.

"If we really are eating much less, it suggests that policymakers should focus on increasing physical activity – rather than reducing consumption – in order to tackle obesity.

“However, we found that the national surveys used to measure calorie intake are under-estimating how much people are consuming. We also found that this problem has been getting worse over time – so calorie consumption may have been rising, not falling.”

Following its findings, BIT is now calling for policy makers to shift their focus from efforts to increase exercise levels to those looking to lower calorie intakes.

“Our conclusion is that policies to reduce calorie consumption have an important part to play in an obesity strategy,” the report states.

“Although attempts to increasing physical activity should be part of the policy mix, they should not act as a distraction from the central importance of reducing calorie consumption.”

The report’s findings are likely to cause a stir among those driving efforts to improve the UK’s record-low physical activity levels.

Responding to the report, Steven Ward, executive director of ukactive, said physical inactivity and obesity are “two separate issues often wrongly conflated”.

“Unfortunately, there is a lot of misunderstanding around the topics of obesity and physical inactivity," he said.

“We, and a growing number of the world’s leading health academics, have always been clear that obesity and physical inactivity are two distinct public health concerns of equal importance, which we must tackle by leading healthier lifestyles.

“Physical inactivity is a top-level health concern in its own right and the benefits of exercise cannot even begin to be measured by looking solely at waistlines.

“Physical activity has been hailed by doctors as a miracle cure which can help to treat and prevent more than 20 lifestyle-related diseases including cancer, heart disease, stroke and diabetes.

“Research from Cambridge University shows there are currently twice as many Europeans dying from physical inactivity as there are from obesity, while the recent study in The Lancet showed inactivity causes more deaths globally than smoking.

“We should follow the lead of NHS chief executive Simon Stevens, who is currently implementing an integrated workforce wellness programme for NHS staff which seeks to tackle inactivity through a range of exercise initiatives and overcome obesity by offering healthier food options.”

The Behavioural Insights Team (BIT) is a part-privatised government agency tasked with encouraging people into making better life choices.

Dubbed the government’s “nudge unit”, it started life inside 10 Downing Street in 2010 as the world’s first government institution dedicated to the application of behavioural sciences.

To read the full Counting Calories: How under-reporting can explain the apparent fall in calorie intake report, click here.