The idea that sex burns calories is nothing more than a myth, according to a new study.
Dr. David Allison, associate dean for science in the School of Public Health at the University of Alabama at Birmingham, and his team have identified seven obesity-related myths that they said were not scientifically-backed by evidence.
One myth the researchers busted was that losing lots of weight rapidly might cause the weight to come back one day, whereas slow, gradual weight loss will accumulate over time to produce longer-lasting changes.
The researchers found evidence that people who lose more weight rapidly are more likely to weigh less, even after several years, CBS News reported.
The oft-told advice that people should set realistic weight loss goals or else they'll become frustrated and not lose weight is a myth, according to the study, which cited data that people may actually do better with more ambitious goals.
Other major myths busted include the idea that breast-feeding may reduce a child's risk for obesity.
While breast-feeding may offer benefits to both mom and baby, evidence does not suggest preventing obesity is one of them, the researchers said.
It is said that having sex is just like exercise, and can cause people to lose 300 calories.
But the researchers said people would be lucky to burn one-twentieth of that during sex, which offers about the same calorie expenditure from sitting on a couch.
For example, a 154-pound man in his early-to-mid 30s who has sex for six minutes will expend about 21 calories during intercourse, they wrote.
Their results are published online in the New England Journal of Medicine.