Adults in the UK are underestimating the calories they consume by 50%, according to new statistics.
Data suggests that men consume 1,000 more calories than they think every day, while women eat the equivalent of 800 calories more than their estimates.
The findings shed light on a long standing public health mystery.
Over the last 40 years, official statistics show the number of calories people consume has dropped – however, the population has continued to gain weight.
The steady increase in obesity could be down to people failing to accurately assess the amount of calories they eat.
In the study, published by the Office for National Statistics, men on average estimated that they consumed about 2,100 calories, and women 1,600.
But when scientists made a more accurate assessment of what participants had consumed they found a calorie count that was much higher: with men consuming an average of 3,119 calories every day, and women 2,393.
Researchers used a technique called doubly labelled water, which tracks how much energy is expended by analysing urine and is considered the “gold standard” for measuring calorie consumption.
Government statistics suggest more than 58% of women and 68% of men are overweight or obese, while one in four UK adults are classed as obese, according to the UN.
The count puts Britain at the top of Europe’s obesity league table, with 21.3% of Germany’s population and 15.6% of France’s population ranked obese or overweight.
The study also found that estimates of calorie consumption were lower than recommended guidelines – nearly 80% of participants suggested their daily calorie counts were below the requirements for their age and sex.
The differences between reported and actual calorie intake ranged from 598 to 3,671 calories – and a small number of people guessed they consumed more calories than they actually did.