“Forget going for a stroll – try sexercise: Average session burns more calories than a walk – but less than a jog,” reads today’s Mail Online.
The idea that sex can help burn off calories has long been a staple of magazines and daytime chat shows. In fact, no-one has accurately measured how many calories are expended during sex.
The current research attempted to fill this research void by recruiting 21 young couples whose energy expenditure during sex was measured and compared with 30 minutes of moderate intensity on a treadmill.
So did sex match the treadmill in terms of energy expenditure? The short answer is no, at least not in this small and strictly defined group.
The researchers found the energy expenditure of sexual activity was significantly less than expended during the 30 minutes of treadmill exercise – around two-thirds less. For example, men’s average energy expenditure during sexual activity was 101 calories but 276 calories on the treadmill.
However, as the researchers put it “almost all of the participants reported that sexual activity was more pleasant than the treadmill exercise" – so sex seems to have an upside.
Where did the story come from?
The study was carried out by researchers from universities based in Quebec, Canada and was funded by grants from The Foundation for the Scientific Study of Sexuality and l’Institut Santé et Société of the Université du Québec à Montréal.
The Mail Online coverage was generally accurate, however the statement that an “average session burns more calories than a walk – but less than a jog” is based on a series of assumptions, for example, how long would the jog last, rather than being tested directly.
What kind of research was this?
This experimental study looked at the energy expenditure during sexual activity in young healthy couples in their natural environment and compared it to moderate exercise.
Why you might want to investigate this from a medical point of view is perhaps less obvious. The authors describe how health professionals are beginning to recognise that sexual activity could have an important influence on overall health and quality of life. The rationale seemed to be aimed at getting a better idea of the extent to which sex was or could contribute to recommended levels of physical activity in young people, and how it measured up to other activities like jogging.
What did the research involve?
Twenty-one heterosexual couples from the Montreal region of Canada were recruited to the study between September 2012 and April 2013.
Participants were only included if:
- they were aged between 18-35 years old
- they were born in the province of Quebec and French speaking
- they were Caucasian
- they were non-sedentary (did more than two hours a week of structured exercise)
- they had no sexual dysfunctions – i.e. premature ejaculation or erectile dysfunction
- be sexually active (at least one sexual activity per week)
- they were in a loving, monogamous and stable relationship with their partner for a duration of between six and 24 months
- the women in the partnership were using oral contraception
All participants also reported no cardiovascular diseases, diabetes or any orthopaedic limitations, such as problems with bones or joints.
All participants completed one endurance exercise session at the start of the study which consisted of a five-minute warm-up (walking) followed by 30 minutes of exercise on a treadmill at moderate intensity. The goal, the authors reported, was to use an exercise that could be regularly practised by the general population to act as an activity to compare sex against.
Exercising a minimum five times per week for 30 minutes at moderate intensity is also the amount the general population are recommended to engage in to help maintain a healthy lifestyle – a total of at least 150 minutes per week.
Energy expenditure (measured in calories) and intensity (measured in a unit called MET, metabolic equivalent task) during sexual activity and the endurance exercise was measured using a portable mini SenseWear armband.
The portable armband uses a 3-axis accelerometer (a device used to measure physical movement), a heat flux sensor, a galvanic skin response sensor, a skin temperature sensor, and a near-body ambient temperature sensor to capture data used to estimate energy expenditure.
Perceived energy expenditure, perception of effort, fatigue and pleasure were also assessed after sexual activity via a seven-point questionnaire.
Sexual activity was defined as the onset of foreplay, intercourse and at least one orgasm by either the man or woman and ended at the couple’s discretion. During a one month period, couples were instructed to perform one sexual activity per week in their homes so all couples had performed a total of four sexual activities. The couples were instructed to perform their usual sexual activities and not to use any drugs, alcohol or medication for erectile dysfunction (such as Viagra) before the sexual activity.
The main analysis compared the duration and intensity of the average sex session to the endurance exercise.
What were the basic results?
The average length of a sexual activity was 24.7 minutes (range 10 to 57 minutes). Average energy expenditure during sexual activity was 101 calories (4.2 calories per minute) in men, higher than that seen in women at 69.1 calories (3.1 calories per minute).
Energy expenditure through sexual activity was significantly less than the energy expended during the 30 minutes of exercise – which was 276 calories (9.2 calories per minute) for men and 213 calories (7.1 calories per minute) for women.
Average sexual activity intensity was 6.0 METs in men and 5.6 METs in women, which represents a moderate intensity of exertion. This was again less than the intensity of the endurance exercise in men 8.5 METs and women 8.4 METs.
It was estimated that sexual activity represented around 71% of the intensity of the 30-minute endurance exercise, and 38% of the energy expenditure.
The highest range value achieved by men for absolute energy expenditure during sexual activity (306 calories) can potentially be higher than that of the mean absolute energy expenditure of the 30-minute exercise session (276 calories), whereas this was not observed in women.
Perceived energy expenditure during sexual activity was similar in men (100 calories) and in women (76.2 calories) when compared to measured energy expenditure, indicating they were good judges of their level of energy expenditure.
Only 5% of all participants reported that sexual activity was more strenuous when compared to the 30-minute treadmill exercise.
How did the researchers interpret the results?
The interpretation from the researchers was that “energy expenditure during sexual activity appears to be approximately 85 calories or 3.6 calories per minute and seems to be performed at a moderate intensity in young healthy men and women. These results suggest that sexual activity may potentially be considered, at times, as a significant exercise.”
In their discussion of the intensity of the exercise the researchers’ reported the level of intensity that is exerted from sexual activity “could be” higher than walking at 4.8 km/hour but lower to that of jogging at 8 km/hour. And that the level of intensity of sexual activity in the study “may give health professionals a better understanding on the potential risk for myocardial infarction in cardiac patients since this topic appears to be a preoccupation in the field of medicine.”
This study found the energy expenditure and intensity of sexual activity in 21 healthy young heterosexual couples was significantly less (approximately 38% of the total) than that expended during a 30-minute treadmill exercise at moderate intensity.
Some men exerted more energy during sex than the average expended on the treadmill, but this was the exception among men and was not seen in any women.
The practical implications of the research aren’t too clear. Arguably, the results are of more interest on a sociological level; we may live in a more open society compared to the past but the"nuts and bolts" of sex, such as "how often" or "how long?", remain very much a taboo subject for many people.
However, the authors’ hint that health professionals might find it useful to know that sexual activity may not be contributing to the recommended weekly physical activity tally.
A significant limitation of the study was it’s stringent inclusion and exclusion criteria. This meant the study group was very homogenous (comprising of similar traits) and not very representative of a diverse general population. The results are mostly applicable to young (average age 22.6 years), healthy, heterosexual, sexually active couples in stable relationships.
The researchers’ placed the energy expenditure of sexual activity in their study somewhere between a walk and a jog. This was based on a comparison with results from other studies presented in their discussion; it was not tested directly so it is unclear how accurate this estimate is.
It was also not clear how accurate the SenseWear armband was at measuring energy expenditure and intensity so the precise calorie estimates of the different physical activities may contain some error.
The researchers noted that the sexual intensity of sexual activity in their group (six METs in men) was much higher than those found in previous studies reporting three to four METS. This may highlight that sexual activity intensity and energy expenditure varies a lot among different people, or that the couples were more active than usual during sex because they knew they were being monitored.
The bottom line from this research was that sex did not appear to be on the same level as 30 minutes of moderate exercise on a treadmill, the recommended minimum level of activity to be achieved five times per week.
If you want more frank advice about sex and ways you could improve your relationship with your partner, read talking about sex.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Daily Mail, 29 October 2013
Links to the science
PLOS One. Published online October 29 2013