Men are almost four times as likely as women to have a poor grasp of how many calories they need to consume daily for their age and activity level, a US study suggests.
American obesity rates are at historically high levels, researchers note in the Journal of the Academy of Nutrition and Dietetics.
An estimated 40 per cent of adults, or more than 93 million people nationwide, are obese.
While obesity has many causes, consuming too many calories is a big part of the problem.
For the study, researchers examined data on 6,267 adults surveyed about their health and eating habits from 2007 to 2008 and 2009 to 2010.
Overall, 37 per cent of men and 17 per cent of women were unable to correctly answer questions about how many calories they would need daily to maintain their current weight, based on their age, sex and activity levels, the study found.
The sex gap in calorie knowledge persisted across racial and ethnic groups as well as different ages, incomes and education levels.