Sexual Functioning and Obesity: A Review
We review the literature on the relationship between obesity and sexual functioning. Eleven population-based studies, 20 cross-sectional non-population-based studies, and 16 weight loss studies are reviewed. The consistency of findings suggests that the relationship between obesity and reduced sexual functioning is robust, despite diverse methods, instruments, and settings. In most population-based studies, erectile dysfunction (ED) is more common among obese men than among men of recommended weight. Studies of patients in clinical settings often include individuals with higher degrees of obesity, with most studies showing a relationship between obesity and lower levels of sexual functioning, especially ED. The few studies that include both genders generally report more problems among women. Most studies of patients with comorbidities associated with obesity also find an association between obesity and reduced sexual functioning. Most weight loss studies demonstrate improvement in sexual functioning concurrent with weight reduction despite varying study designs, weight loss methods, and follow-up periods. We recommend that future studies (i) investigate differences and similarities between men and women with respect to obesity and sexual functioning, (ii) use instruments that go beyond the assessment of sexual dysfunction to include additional concepts such as sexual satisfaction, interest, and arousal and, (iii) assess how and the degree to which obese individuals are affected by sexual difficulties. Given the high prevalence of obesity and the inverse association between body mass and sexual functioning, we also recommend that sexual functioning should be more fully addressed by clinicians, both in general practice and in weight loss programs.
The adverse effects of obesity on health-related quality of life are well documented (1,2,3). An important aspect of health-related quality of life, sexual functioning, has become a topic of growing interest in the obesity field. In a review paper published in 2007 (4), Larsen and colleagues describe results of four prospective and seven cross-sectional studies of obesity and erectile dysfunction (ED), one cross-sectional study of obesity and female sexual functioning, and seven weight loss studies as they relate to sexual functioning. Results of their review indicate that obesity is associated with ED in both prospective and cross-sectional studies, weight loss is associated with improved sexual functioning in both men and women, and the study of female sexual functioning and obesity has not been adequately described. Due to the large number of studies that have been published since the Larsen et al. review (28 studies), the present review was undertaken.
The articles for the current review were identified through PubMed and PsycINFO search engines and also by searching for references cited within the obtained articles. Search terms were used to identify studies that pertained to BOTH weight, BMI, weight loss, bariatric surgery, gastric bypass surgery, Roux en Y, or obesity AND sexuality (i.e., sexual, sexuality, libido, sexual behavior), sexual dysfunction (i.e., erectile function, ED, impotence, sexual disorder, female dysfunction, psychological sexual dysfunctions, physiological sexual dysfunction), sexual functioning, or erectile function. In addition, specific sexual questionnaires (i.e., Sexual Function Questionnaire, Female Sexual Function Index (FSFI), International Index of Erectile Function, and Derogatis Sexual Functioning Inventory) were used as search terms, and studies were included if their focus was on the relationship between these questionnaires and weight, BMI, weight loss, or obesity.
Although body image and marital satisfaction are concepts related to sexual functioning, we considered these to be outside the scope of the present review. We included studies on sexual abuse only if they specifically assessed sexual functioning as the key variable. We included studies of weight-specific health-related quality of life only if their primary focus was on sexual functioning or sexual quality of life.
The literature search was limited to human participants and studies published in English. This search was conducted by the second author with the assistance of a clinical librarian. Only peer-reviewed research articles that included obese participants were included. Unpublished research was not considered (e.g., dissertations, abstracts). A total of 102 studies were considered for inclusion in this review.
Assessment of Sexual Functioning
The study of sexual functioning is complicated by the different definitions used to describe functioning/dysfunction, the different aspects of sexual functioning that are relevant to each gender, and the numerous and diverse assessment methods that have been used (i.e., validated instruments that are gender-specific, validated instruments that are used for both genders, study-specific questionnaires, and clinician-driven patient interviews). As a result, interpretation of results across studies is complicated by these dissimilarities.
Some measures of sexual functioning have been more rigorously developed and validated. These include the Brief Sexual Function Inventory (BSFI) (5), Erection Quality Scale (EQS) (6), FSFI (7), International Index of Erectile Function—standard (IIEF) and abridged versions (IIEF-5; SHIM) (8,9), and the Sexual Quality of Life-Female questionnaire (SQOL-F) (10). (A Supplementary Table S1 online is provided that describes in detail the characteristics of 15 of the most commonly used measures of sexual functioning.)
Population-Based Studies of Obesity and Sexual Functioning
Table 1 presents findings from population studies of obesity and sexual functioning. Two studies included both men and women, seven studies included men only, and one study included women only. Diverse methods were used to assess sexual functioning, including study-specific questionnaires, in-person interviews, telephone surveys, and validated questionnaires. Despite the heterogeneity of methods and the diverse geographical settings, all except one population-based study of men (11) showed a higher occurrence of ED in obese men than healthy weight men. Several studies compared the relative effect of obesity on ED with the relative effect of other factors (e.g., medical conditions, physical activity, age, and smoking status), with some studies finding similar effect (12,13,14), others finding a greater effect for other factors (11,15), and some finding a greater effect for obesity than other variables (16). One population-based study found that BMI was associated with sexual dysfunction for men, but not for women (17). Only one population-based study of women was identified, with results indicating that overweight/obese women were more likely than healthy weight women to report ever having sexual intercourse (18).
Table 1. Population-based studies of obesity and sexual functioning
Cross-Sectional, Non-Population-Based Studies of Obesity and Sexual Functioning
Table 2 presents findings from cross-sectional, non-population-based studies of obesity and sexual functioning. Studies based on patients in clinical settings tended to include individuals with higher degrees of obesity. In the two studies that assessed both men and women (19,20), women reported poorer sexual functioning than men. Results of studies of women only showed mixed findings. In the one study of men only, obesity was associated with greater ED impairment for men already diagnosed with ED (21).
Table 2. Cross-sectional, non-population-based studies of obesity and sexual functioning
Obesity and Sexual Functioning in Individuals with Obesity-Related Comorbid Conditions
A series of studies on sexual functioning have been conducted in individuals with obesity-related comorbid conditions. Such conditions include urinary incontinence (22,23,24,25), polycystic ovary syndrome (26,27), obstructive sleep apnea (28), binge eating disorder (29), metabolic syndrome (30,31), diabetes (32,33), and prostate cancer (34). In most of these studies there was an association between obesity and impairment in sexual functioning. For the studies of individuals with urinary incontinence, results were inconsistent regarding the association between obesity and sexual functioning. For the studies of individuals with polycystic ovary syndrome, BMI appeared to have a modest or limited impact. For the one study of men with diabetes, high BMI increased ED risk in type 1 diabetes, but not in type 2 diabetes (32), and for the one study of women with type 2 diabetes, BMI was a risk factor for female sexual dysfunction (FSD) (33). For the one study on prostate cancer, the relationship between BMI and ED was not significant.
Changes in Sexual Functioning After Weight Loss
RCTs: nonsurgical weight loss studies
Randomized controlled trials (RCT's) are usually considered to provide the strongest scientific evidence when considering the effect of an intervention. Two long-term RCT's (35,36) of nonsurgical weight loss treatment in men showed significant improvement in sexual functioning [assessed by the IIEF] in the intervention groups compared to the control groups. One trial (n = 372; mean BMI = 35.3; mean age = 60.5) (35), a comparison of an intensive lifestyle intervention for men with type 2 diabetes with support/education for men with type 2 diabetes, concluded that the weight loss intervention was “mildly helpful” in maintaining erectile function. Despite overall mean differences between the groups in IIEF scores at 1 year, 8% of men in the lifestyle intervention reported worsening erectile function and 22% reported improvements, compared to the control group in which 20% reported worsening and 23% reported improvements. The other trial (36) delivered monthly group sessions and detailed instruction regarding caloric intake, self-monitoring, goal setting, and physical activity as the active treatment (n = 55 men with ED; mean BMI = 36.9; mean age = 43.5) and general information about healthy food choices and physical activity for the control group (n = 55 with ED; mean BMI = 36.4; mean age = 43). At 2-year follow-up, BMI had decreased in the intervention group and IIEF scores showed significant improvement, whereas the control group had stable IIEF scores and less change in BMI. About one-third of study participants no longer scored in the ED range at follow-up. Reduction in BMI and increased physical activity both predicted improvements in IIEF scores.
Two medium-term (6–8 months) RCT's (one in men and one in women) found no significant improvements in sexual functioning despite greater weight reductions in the intervention groups. In one of these trials (37) the intervention group (n = 19 men; mean BMI = 39.3; mean age = 45.9) received a very low-energy diet and behavior modification program and the control group (n = 19 men; mean BMI = 39.4; mean age = 47.2) received no intervention. Erectile function was assessed using the IIEF and the Sexual Activity Scale (38) (consisting of one item, “How often do you and your partner engage in sexual activity, with or without intercourse?”). Although at 8 months the intervention group had significantly more weight loss and increased serum testosterone compared to the control group, there were no significant improvements on any IIEF domains or in sexual activity.
A 6-month RCT assessed the effects of an intensive lifestyle weight loss intervention vs. structured education on sexual functioning in 338 women with urinary incontinence (mean BMI = 36–37; mean age = 53) (23). Participants were administered questionnaire items drawn from the FSFI and the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (39), adapted to assess functioning in the three months prior to each visit. No significant differences in sexual functioning were found between groups despite greater weight reduction in the intervention group.
A short-term (8-week) RCT (40) of a weight loss medication (sibutramine) plus behavior therapy vs. behavior therapy alone found significant improvements in sexual functioning (FSFI total score and domain scores relating to arousal, orgasm, and sexual satisfaction) in women in the sibutramine group (n = 24 women; mean BMI = 26.9; mean age = 34.5) compared to controls (n = 22 women; mean BMI = 28.0; mean age = 36.6). Regardless of treatment group, decreases in BMI were associated with improvements in arousal and orgasm.
In summary, three out of five nonsurgical RCT's found positive effects of weight loss on sexual functioning. In the two studies that showed no effect one had a small sample size (n = 38) (37) and the other was in women with incontinence (23), who may require greater weight loss or improvements in incontinence before they experience an improvement in sexual functioning.
RCTs: surgical weight loss studies
A long-term (24-month) RCT of intensive lifestyle modification followed by subsequent gastric bypass found significant improvements in erectile function (using the abbreviated IIEF-5) for the intervention group (n = 10; mean BMI = 55.7; mean age = 36.7) compared to controls (n = 10; mean BMI = 54.0; mean age = 42.2) (41). Although improvements in erectile function were demonstrated, this was a very small trial (10 participants in each arm).
Nonrandomized, controlled weight loss studies
Results of two nonrandomized studies of the effects of weight loss on sexual functioning in men found significant improvement in sexual functioning relative to control groups. Two-year changes in sexual functioning (42) were studied in 22 male gastric bypass patients (mean age = 49.9; mean BMI = 44.9) compared to a control group of 42 obese men (mean age = 47.3; mean BMI = 48.9). Sexual functioning was assessed using the four sexual life items from the Impact of Weight on Quality of Life-Lite (IWQOL-Lite) questionnaire (43). At 2-years post-surgery BMI decreased by an average of 16.6 units (± 1.2) and all indices of sexual functioning improved significantly from baseline, whereas sexual functioning did not change in the control group.
The effects of an 8-week, low-energy meal replacement diet on sexual functioning and lower urinary tract symptoms were evaluated in men with and without diabetes (44). Nineteen men with diabetes (mean BMI = 35.1; mean age = 58.1) and 25 men without diabetes (mean BMI = 35.7; mean age = 44.5), were assigned to a dietary intervention, compared to 24 age-and BMI-matched controls (mean BMI = 33.1; mean age = 48.4). Scores on the IIEF-F and Sexual Desire Inventory (45) improved and testosterone increased for participants in the intervention arm. The degree of weight loss was associated with improvements in both measures of sexual functioning.
In summary, although the weight loss interventions and the lengths of follow-up differed in these two nonrandomized, controlled weight loss studies (one surgical and one medical), results were favorable in both.
Prospective, weight loss studies without controls
Results of five prospective weight loss studies were consistent in finding improved sexual functioning following weight loss. Changes in sexual functioning were evaluated over a 2-year period in 161 obese women (mean age = 44.3; mean BMI = 40.3) and 26 men (mean age = 48.7; mean BMI = 43.3) undergoing nonsurgical weight loss treatment (46). Six dimensions were measured using items from the IWQOL questionnaire (47,48). At the 2-year evaluation weight loss (averaging 13.1%) was significantly associated with improvements in all dimensions, and a subsequent regain of 3–4% body weight did not negatively affect sexual functioning.
Changes in sexual functioning were evaluated in 97 men (mean age = 48; mean BMI = 51) pre- and post-gastric bypass surgery (mean follow-up of 19 months, range 6–45 months) using the BSFI (49). Scores improved on all domains of the BSFI postoperatively, with amount of weight loss independently predicting degree of improvement. After an average excess weight loss of 67%, BSFI scores approached those of age-based norms. The authors estimated that a man who is morbidly obese has the same degree of sexual dysfunction as a nonobese man ∼20 years older.
Another prospective weight loss study evaluated sexual functioning (using the FSFI) pre- and post-bariatric surgery in 102 sexually active women (50,51). At 6-months post-surgery and a mean percent of excess weight loss of 42.3%, FSD had resolved in 68% of the cases, and only one woman developed FSD post-surgery. Scores on the FSFI for the entire sample exhibited significant improvements pre- to post-surgery on all domains, with post-operative scores comparable to published norms. Being married, younger, and having poorer preoperative sexual functioning were related to greater improvements on the FSFI.
Sexual functioning was evaluated pre- and 1-year post-surgery in 60 women (mean BMI = 51.9; mean age = 35.7) in another prospective study (52). Patients experienced statistically significant improvements in all FSFI domains except orgasm, along with reductions in BMI.
Finally, sexual functioning was evaluated in 116 female patients pre- and 1-year post-gastric banding using semistructured interviews (53). Before surgery low sexual desire was reported by 11.2% of patients, sexual avoidance by 23.3%, and difficulty engaging in sexual intercourse because of physical problems by 11%. After surgery, with a mean change in BMI from 42.8 to 33.1, 63% of patients reported enjoying sex more after surgery, compared with 12% who enjoyed sex less after surgery.
In summary, results of five prospective, uncontrolled weight loss studies provide further evidence of a treatment effect. Three of these studies included women only, one included men only, and one included both. In four studies weight loss was achieved through bariatric surgery and in one study a nonsurgical treatment was administered. Length of follow-up varied from 6 months to 2 years.
Retrospective weight loss studies without controls
Two of three retrospective weight loss studies without controls reported improved sexual functioning associated with weight loss. Thirty-two obese women (mean BMI = 42.7; mean age = 47) were evaluated after completion of at least 11 weeks in a hospital-based multidisciplinary weight loss program (54). Participants were given questionnaires derived from the drive subscale, satisfaction subscale, and Global Sexual Satisfaction Index of the Derogatis Sexual Functioning Inventory (55) and instructed to answer them retrospectively and at the end of treatment. Participants reported significant improvements for the drive subscale and the Global Sexual Satisfaction Index, as well as decreased BMI.
Using a study-specific questionnaire, Camps and colleagues studied 28 patients (64% women, mean age = 45) who had undergone vertical banded gastroplasty 1–11 years earlier (56). Fifty percent of patients and 64% of partners reported improved sexual enjoyment at follow-up.
Unlike these two studies, another retrospective study of the effects of laparoscopic gastric banding on sexual functioning in men found no improvement in IIEF scores an average of 31.9 months ± 22.3 post-surgery despite large weight reductions (57).
In summary, two of three retrospective weight loss studies provided additional support for improved sexual functioning subsequent to weight loss. Although studies varied with respect to measurement techniques, weight loss treatments, and time frames, and a retrospective design was used, results of these studies were generally consistent with those found in the higher quality studies reported above.
Conclusions and Implications
This review adds to the literature on obesity and sexual functioning by including the most recent studies in this expanding area. We review assessment methods, population-based studies, cross-sectional studies in obese persons and other groups with obesity-related comorbid conditions, as well as studies evaluating change associated with various weight loss interventions, including bariatric surgery. The consistency of findings across studies and methodologies indicates a robust relationship between not only obesity and reduced sexual functioning but also between weight loss and improved sexual functioning.
Our review found that population-based studies of men show a higher occurrence of ED in obese men than in healthy weight men. Fewer population-based studies have included women. In two of the three studies that included women, obesity was not related to sexual functioning or sexual satisfaction (17,58), but the third study reported that overweight/obese women were more likely to report ever having sexual intercourse than healthy weight women (18).
Studies based on patients in clinical settings often included individuals with higher degrees of obesity, with most showing an association between obesity and lower levels of sexual functioning, especially ED. Furthermore, the few studies that included and compared men and women tended to report more problems among women. Studies of women only showed mixed findings. In most studies of obese individuals with obesity-related comorbid conditions, there was also an association between obesity and reduced sexual functioning. It is notable that clinical studies tended to show more problems among women related to their weight, while population studies tended to show more sexual difficulties among men related to obesity. This may indicate that men are less likely to seek help, not only for obesity, but also for sexual difficulties. This is an interesting area for further, more in-depth, studies.
Although most studies imply that the causal direction is from obesity to reduced sexual functioning, given that most are cross-sectional, the reverse causal relationship, reduced sexual functioning leading to obesity, through reduced physical activity or increased food intake, is also plausible. Finally, a third explanation, underlying psychiatric, psychological or physiological/ hormonal problems leading to both weight gain and to reduced sexual functioning, cannot be discarded.
We identified 16 studies that assessed changes in sexual functioning subsequent to weight loss interventions. Eight of these studies were conducted with men only (four nonsurgical interventions; four surgical interventions), six with women only (three nonsurgical interventions; three surgical interventions), and two with both men and women (one nonsurgical intervention; one surgical intervention). Results of long-term RCT's of weight loss interventions (i.e., studies lasting 1 year or more) provided strong and consistent evidence of the positive effects of weight loss on sexual functioning for men. Most other weight loss studies, conducted using various study designs, weight loss methods, and follow-up periods, also provided evidence for the benefits of weight loss on sexual functioning for both men and women.
A large proportion of the studies reviewed were based on men only or women only; even the studies that included both rarely compared sexual functioning in men and women. Acknowledging that sexual functioning is clearly anatomically, physiologically, and probably psychologically different in the two genders, more studies to investigate differences, as well as similarities, between obese men and women seem worthwhile. Because most measures of sexual functioning are designed for men only or women only, exploration of differences/similarities in sexual functioning between men and women would require use of an instrument designed for both genders, such as the Sexual Functioning Questionnaire (SFQ) (59) or the Derogatis Sexual Functioning Inventory (55).
One of our observations in conducting this review is that the majority of studies have focused on sexual dysfunction, especially ED. We recommend a change in focus from the assessment of specific sexual dysfunctions to the assessment of sexual functioning more broadly defined. Measures that assess sexual satisfaction, desire, as well as dysfunction, such as the FSFI, SFQ, and BSFI, provide this broader view. In addition, we propose that future studies of sexual functioning and its relation to obesity include evaluations of how affected men and women are by any sexual difficulties they experience and to what degree their sexual life impacts their quality of life. Only one instrument has been identified that assesses the impact of sexual dysfunction on sexual quality of life—the SQOL-F, which is for women only. We are aware of no studies on the relationship between sexual functioning/sexual dysfunction and other aspects of quality of life.
Due to the high and rising prevalence of obesity (60), and especially of extreme obesity (61), we are concerned that difficulties with sexual functioning are also becoming more common. It is clear from the current review that obesity has a negative effect on sexual functioning. The silver lining is that most studies of weight loss and sexual functioning show that sexual functioning can be improved with weight loss.
Given the well-documented association between obesity and reduced sexual functioning, we believe that sexual functioning should be more fully addressed by clinicians, both in general practice and in weight loss programs. Sexual concerns may be addressed by asking a few simple open-ended questions during initial screening (e.g., “Do you have any concerns about any other areas of your life that we have not yet discussed?”) followed by a long pause to allow the patient to respond. A second, more targeted, question may be asked, such as, “Are you experiencing any concerns in your personal or sexual life?” If concerns about sexual functioning are elicited, then listening to these concerns with empathy and putting the concerns into perspective by describing their high prevalence in this population would likely be beneficial. Highlighting the likely benefits of weight loss on sexual functioning may also be motivating to some patients. Patients being evaluated for bariatric surgery may be particularly likely to have difficulties with sexual functioning (19,49), and thus it is especially important for clinicians to inquire about sexual functioning in these patients.
In summary, the present review updates the earlier Larsen review by including 28 additional studies and providing broader coverage of this topic. In addition to reporting results of population-based studies and cross-sectional studies, we included a review of assessment methods, studies of individuals with obesity-related comorbid conditions, and studies evaluating changes associated with various weight loss interventions, including bariatric surgery. Whereas the Larsen review included only one study of FSD, the current review reported on six cross-sectional studies that included women and two additional population studies of women. We also noted that clinical studies tended to show more problems among women related to their weight, while population studies tended to show more sexual difficulties among men related to obesity. Furthermore, we proposed that future studies of sexual functioning and its relation to obesity include evaluations of how affected men and women are by any sexual difficulties they experience and to what degree their sexual life impacts their quality of life (i.e., not simply assessing sexual dysfunction).
Supplementary material is linked to the online version of the paper at http:www.nature.comoby
We acknowledge the assistance of Mary J. Markland, MA, AHIP, Clinical Campus Librarian at University of North Dakota School of Medicine and Health Sciences.
The first author receives royalties from Duke University for use of the IWQOL-Lite.
See the online ICMJE Conflict of Interest Forms for this article.