The study reports that the rate of unplanned pregnancies is four times higher among single obese women than normal weight women, despite them being less likely to have been sexually active in the past year. Obese women are less likely to seek contraceptive advice or to use oral contraceptives. Obese men have fewer sexual partners in a 12 month period, but are more likely to suffer from erectile dysfunction and develop sexually transmitted infections than normal weight men.

Obesity is emerging as one of the fastest growing pandemics in modern times says the study, but its effects on sexual health are unclear. The research led by Professor Nathalie Bajos, Research Director at the Institut National de la Santé et de la Recherche Medicale in Paris, is the first major study to investigate the impact of being overweight or obese on sexual activity and sexual health outcomes such as sexual satisfaction, unintended pregnancy and abortion.

The authors undertook a survey of sexual behaviours among 12,364 men and women aged between 18 and 69 years of age living in France in 2006. Of the participants, 3,651 women and 2,725 men were normal weight (BMI between 18.5 and 25), 1,010 women and 1,488 men were overweight (BMI between 25 and 30) and 411 women and 350 men were obese (BMI over 30).

The results show that obese women were 30% less likely to have had a sexual partner in the last 12 months. Obese men were 70% less likely to have had more than one sexual partner in the same period and were two and half times more likely to experience erectile dysfunction.

Sexual dysfunction was not associated with BMI among women. However, obese women under 30 were less likely to seek contraceptive advice or use oral contraceptives. They were also more likely to report an unintended pregnancy. Obese men under 30 were far more likely to have had a sexually transmitted infection.

Obese women were also five times as likely to have met their partner on the internet, more likely to have an obese partner, and less likely to view sex as important for personal life balance. The authors suggest that social pressure, low self-esteem and concerns about body image may help explain these findings.

The authors conclude that the public health impact of these findings is important. They say: "The scale of the problem and the magnitude of the effects (particularly the fourfold increase in risk of unintended pregnancy among obese women) warrants focused attention. In terms of targeting advice and care, a considerable proportion of the population is obese, is easily identified as such, as is at increased risk in terms of poorer sexual health status."

In an accompanying editorial, Dr Sandy Goldbeck-Wood, a specialist in psychosexual medicine, points to evidence showing that doctors find it difficult to discuss sex and weight issues with patients, and believes that clinicians must be prepared to address these difficult subjects which have such important effects on health and quality of life. She says: "We need to understand more about how obese people feel about their sex lives, and what drives the observed behaviours and attitudes."

She concludes: "In public health terms, the study lends a new slant to a familiar message: that obesity can harm not only health and longevity, but your sex life. And culturally, it reminds us as clinicians and researchers to look at the subjects we find difficult."

Note: If no author is given, the source is cited instead.

• Obesity
• Sexual Health
• Erectile Dysfunction

• Gender Difference
• Relationships
• Dieting and Weight Control

• Body mass index
• Sexual dysfunction
• Nutrition and pregnancy
• Overweight
• Fertility
• General fitness training