Most heat is not lost through the head, as previously thought
If you've ever blamed sweets for your out-of-control children or been told not to eat too late because it'll make you fat, you might want to think again.
Two researchers in America say those and other similar beliefs are often inaccurate and shouldn't be believed.
Rachel Vreeman and Aaron Carroll from the Indiana University School of Medicine looked at studies and searched the web to investigate the theories.
They claim many are medical myths with little scientific backing.
The pair say many parents think sugar from sweets and chocolate makes children hyperactive but in fact research shows the link is most likely in parents' minds.
At least 12 clinical studies have found no evidence of differences in behaviour between children given sugar and those given none.
"Even in studies of those who were considered 'sensitive' to sugar, children did not behave differently after eating sugar-full or sugar-free diets," the authors wrote.
Similarly eating too late at night might not necessarily cause weight gain.
One Swedish study appeared to support the theory, with obese women reported eating more at night than non-obese women.
But the researchers say that obese women didn't just eat more at night but also ate more at other times of the day.
Rachel Vreeman and Aaron Carroll said: "In the pursuit of scientific truth, even widely held medical beliefs require examination or re-examination.
"The holiday season presents a further opportunity to probe medical beliefs recounted during this time of year."
They say another myth is the mistaken belief that most body heat escapes through the head, making it important to wear a woolly hat when the temperature drops.
"If this were true, humans would be just as cold if they went without trousers as if they went without a hat," Rachel Vreeman and Aaron Carroll said.
"But this patently is not the case."
Other debunked medical myths include aspirin curing hangovers.
The researchers said: "From aspirin to bananas to Vegemite and water, internet searches present seemingly endless options for preventing or treating alcohol hangovers.
"No scientific evidence, however, supports any cure or effective prevention for alcohol hangovers."