If getting out of bed for a walk or a game of tennis to shed the Christmas pounds feels too much like hard work, scientists have discovered that staying in bed could be just as beneficial.
Researchers found that sex can be as beneficial as many forms of exercise and admit that participants are likely to find it more enjoyable.
Men on average burn 120 calories during lovemaking while women lose around 90, the equivalent of a brisk uphill walk, a game of doubles tennis or a 15 minute jog.
And at peak times men were found to burn as many calories as running for 30 minutes on a treadmill.
The couples were instructed to perform their usual sexual activities and not to use drugs, alcohol or medication for erectile dysfunction such as Viagra.
The subjects, who were also asked to jog on a treadmill for 30 minutes, were fitted with armbands to measure how much energy they were expending and fill in questionnaires to record their enjoyment.
The researchers recorded the number of calories each person burned and their metabolic equivalent of task (MET), which compares an activity to sitting still, measured at 1-MET.
The results showed that men burned on average 4.2 calories a minute, compared to 9.2 on the treadmill, while women burned 3.1 calories a minute during sex and 7.1 jogging.
The study also recorded an average 6-MET for men during sex and 5.6-MET for women, roughly the same as playing doubles tennis or walking uphill.
"These results suggest that sexual activity may potentially be considered, at times, as a significant exercise,” said lead author Julie Frappier.
"Moreover, both men and women reported that sexual activity was a highly enjoyable and more appreciated than the 30 min exercise session on the treadmill.
"Therefore, this study could have implications for the planning of intervention programs as part of a healthy lifestyle by health care professionals."
When on the treadmill, men recorded an 8.5-MET, while women registered an average 8.4-MET.
But for brief periods during sex, some of the men actually used more energy than they did while on the treadmill.
The results showed most participants (98pc) felt sex was more pleasant compared to the treadmill and 81pc reported a high level of personal pleasure.
"Sexual activity is an important and relevant activity to human life and appears to impact on the mental, physical and social health as well as the quality of life of the individual,” said Miss Frapier.
"Considering that sexual activity may be one of the most regularly practiced activities throughout an individual's life time, it seems important to conduct research on this topic.”
The study, Energy Expenditure During Sexual Activity In Young Healthy Couples, was published by the Public Library of Science.