By Mike Pomranz
Updated July 22, 2015
© Ewing Galloway / Alamy

You’ve just had a solid workout. All those burned calories call for a reward. But how much food can you eat without undoing all that hard work? A new study suggests that people don’t really know.

Researchers looked at 50 adults and 49 adolescents in the United Kingdom who regularly played sports. After an hour of exercise, participants were shown chocolate and sports drinks and asked how much they believed they could consume to compensate for the calories they had just burned. In a move that surprised the researchers, people significantly underestimated how much they could eat or drink – choosing less than half as much as they could have on average.

Those behind the study remained skeptical of the results. “Potentially this might be seen as encouraging, but as we pointed out in the paper, we have qualitative evidence that their intentions would have been to actually eat more when the training had finished, even though they were reporting by underestimating,” Craig Williams, senior author of the paper, told Reuters. William’s believes that participants might have underreported because that’s what they thought researchers wanted to hear.

Williams also said it wasn’t clear whether subjects were unable to estimate how many calories they had burned or how many calories they would be consuming. Either way, the study does show that people are inherently bad at estimating calories with relation to exercise. “We should not become too fixated with trying to be as precise as possible, e.g., to the exact 1 kcal (this would be impossible), but to be able to make better overall estimations,” he said.

Or you could just do it the American way and not exercise at all.