By Lisa Rapaport

(Reuters Health) – 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 U.S. 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% 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 current study, researchers examined data on 6,267 adults surveyed about their health and eating habits in 2007-2008 and 2009-2010.

Overall, 37% of men and 17% 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.

To get the right answer, people had to pick the right calorie range from a list of choices: 500-1,000; 1,001-1,500; 1,501-2000; 2,001-2,500; 2,501-3,000; or more than 3,000.

“So, it’s possible – even likely – that some participants may have simply guessed in the correct range,” said Robin McKinnon, lead author of the study and a senior advisor for nutrition policy at the U.S. Food and Drug Administration (FDA) Center for Food Safety and Applied Nutrition in College Park, Maryland.

“Our analysis probably overestimates rather than underestimates how many people answered correctly,” McKinnon said by email.

The gender gap in calorie knowledge persisted across racial and ethnic groups as well as different ages, incomes and education levels.

About 30% of white men and 56% of black and Hispanic men didn’t know the right range of calories for their weight and age. Nor did 10% of white women, 33% of black women or 42% of Hispanic women.

With less than a high school education, 56% of men and 37% of women didn’t know their daily calorie needs, compared to 24% of men and 6% of women with college degrees. Proportions were similar when comparing men and women with annual incomes under $20,000 versus over $100,000.

The study can’t show whether knowing daily calorie needs impacts how much people actually eat, or whether they are overweight.

“The take-home message is that having a good idea of how many calories your body needs is really helpful for managing your weight – and that men could do (better) to be especially aware of this since they seem to be behind the curve in knowledge of this kind,” said Susan Roberts, a nutrition researcher at Tufts University in Boston who wasn’t involved in the study.

“Another message is that we should all be aware that calorie requirements decrease as we get older and factor that into changing food habits to age in a healthy way,” Roberts said by email.

Calories are not the only thing people need to consider when making choices about what to eat, McKinnon said. People also need to eat a balanced diet.

Dietary guidelines for Americans are available from the U.S. Department of Health and Human Services ( and an easy visual tool for creating balanced meals is available on the U.S. Department of Agriculture’s MyPlate website (

The USDA also has a free online calculator that determines calorie needs based on age, gender, height, weight and activity level (

SOURCE: Journal of the Academy of Nutrition and Dietetics, online July 8, 2019.