The Relationship of Obesity and Overweight with Sexual Function in Women of Reproductive Age: A Systematic Review and Meta-Analysis

Introduction

Obesity and overweight are one of the health problems in all societies, which has an increasing prevalence among adults, young people and even children (1). Obesity is often classified by measuring body mass index (BMI), so that people with BMI between 29.9-25 are overweight and people with BMI above 30 are classified as obese(2).

The prevalence of obesity and overweight is currently estimated at approximately 13-43% in developed countries and 9-40.5% in developing countries. It can also be said that one to two-thirds of people in all societies are overweight (2,3). Like many other developing countries Iran is also, facing an obesity epidemic and its complications, so that the prevalence of obesity in Iran is estimated in the people of 13 years and above 24.9%, in men 26.53% and in women it is estimated to be 27.84 percent (3). The World Health Organization has estimated that by 2030, 59% of men and 65% of women will be obese, which will cause a 67% increase in cardiovascular disorders and a 21% increase in diabetes (4).

 Obesity is considered as one of the threats to public health, obesity and overweight can increase the risk of diseases such as hypertension disorders, metabolic syndrome, diabetes, polycystic ovary syndrome, and obstructive sleep apnea (5). According to the definition of the World Health Organization, health is a multi-dimensional issue that includes not only the physical dimension, but also the psychological and social dimensions. Recently, the concept of sexual health has also been considered in relation to physical and mental health, which the World Health Organization considers to be the harmony and compatibility of physical, emotional, intellectual and social aspects of human sexual affairs. Therefore, it should be noticed that sexual health is an important part of people's lives. It should also be known that different aspects of physical, mental, and sexual health can affect each other and be influenced by each other (6).

Sexual health and the absence of sexual function disorders means that a person enjoys her reproductive and sexual behavior and is far away from factors that inhibit sexual response and disrupt sexual relationships and function. In obese patients negative mental image of the body, low self-confidence, weak interpersonal relationships, and the feeling of shame and guilt caused by these people's weight can be the main factors causing sexual dysfunction because These matters play an important role in sexual relationships. In addition, obesity can be a physical obstacle in sexual relations, therefore, obesity and overweight can be one of the main causes of sexual dysfunction in men and women (7-8).

The mechanisms that can influence the development of sexual disorders in obese and overweight people include: suffering from diseases such as cardiovascular disorders, diabetes, hypertension and hyperlipidemia, and the drugs that are used to treat these illnesses- insulin resistance in obese people and hormonal changes that are related to it and also the cultural and psychological problems caused by obesity (9).

The prevalence of sexual dysfunction in obese and overweight women is reported as 28-45%, and the most common sexual dysfunction in this study is sexual desire and arousal (10). Also, according to the studies which have been done, obesity in women has a negative effect on the stage of the peak of sexual pleasure (orgasm), sexual desire, sexual satisfaction and in men on the stage of ejaculation and erection (11-13). The effect of obesity on sexual disorders is a multifaceted phenomenon that includes: biological, social and psychological factors (14). Studies that have been conducted on the relationship between obesity and overweight with sexual dysfunctions report conflicting results; So that several studies have suggested the existence of a positive relationship between obesity and overweight with sexual dysfunctions (15-16). While a number of studies have not shown any relationship between obesity and sexual dysfunction and consider these are two tottaly unrelated subjects (17-18).

 Bates et al. (2019), in their study showed a statistically significant difference in having sex and sexual function disorders in obese or overweight women compared to normal weight women, so that weight loss has a significant effect on improving function disorders in obese and overweight women (15). Also, Mustafa et al. (2018) showed the relationship between obesity and sexual dysfunction, so that the prevalence of pain during sexual intercourse, difficulties in becoming slippery and defects in sexual arousal in obese women were reported 69/3%, 53/3% and 52% respectively (16). However, the population-based study conducted by Karadag et al. (2014) in Turkey reported that the occurrence of sexual dysfunction in obese women could be due to the other influencing variables such as hypertension, diabetes and cardiovascular disorders. So, obesity is not considered an independent factor in causing sexual dysfunction (17). Rene Moreh et al. (2013) showed that sexual function disorders have a significant relationship with the age of people, but the occurrence of these disorders is not related to obesity or overweight in these people (18). Also Faridi et al. (2013), in their study, showed no significant relationship between obesity and overweight with sexual performance of women (3).

Considering the consequences of obesity and overweight and its impact on marital life, sexual function and fertility in women, scientists are looking for the best solution to improve the personal and social conditions of these people. Also, the level of body mass index is increasing among different societies, and obese or overweight people is being increased, especially among women. Therefore, a definitive conclusion in this field requires more extensive studies on the relationship between obesity and sexual function. Systematic review and meta-analysis are necessary tool to summarize the available evidence in a precise, correct and reliable manner. Despite the fact that several studies have been conducted regarding the effect of obesity on women's sexual function, but conflicting results of these studies made it necessary to conduct a meta-analysis to obtain a clear and consistent result in order to provide a comprehensive guide for researchers and policymakers. Therefore, the present systematic review and meta-analysis was conducted to investigating the relationship between obesity and overweight with sexual function in women of reproductive age.

Materials and Methods

The current systematic review and meta-analysis was conducted based on the guidelines of the Preferred Reporting Items for the Systematic Reviews and Meta-Analyses (PRISMA 2020 check list). For this purpose, the articles indexed in Cochrane databases, Scopus, Web of Science databases, PubMed , SID, Google scholar, Magiran as well as Persian databases of SID and Magiran using English keywords Obesity, overweight , Body Masss Index , ، Sexual dysfunction ,Sexual functioning sexual disorder and their Persian equivalents were searched using Boolean operators OR and AND without time limit until the end of 2024. In order to access more information, the references of the reviewed articles were also reviewed to access other related articles

The inclusion criteria were: observational and descriptive studies in Persian or English related to the purpose of the research. Also, the exclusion criteris included lack of access to the full text of the article and the ahthors were not answering, review studies, letters to the editor, articles presented in conferences, case reports, interventional studies, duplicate documents, articles with incomplete and unrelated data from the study. Independently, all the articles were searched with the keywords mentioned in the title, abstract, and keywords. After removing duplicate studies, the remaining studies were screened and irrelevant articles were removed. Then, the full text of the remaining studies was retrieved and eligible articles were identified and included in the present review.

The quality of the articles included in the systematic review was assessed by using the Newcastle-Ottawa Quality Assessment Scale for observational studies. In order to reduce the bias, the quality of the articles was checked by two independent evaluators, and if there was any disagreement between two evaluators, the article was discussed and reviewed in the presence of another observer to reach a consensus. The Newcastle-Ottawa quality review scale (observational studies version) is a standard scale for evaluating the quality of observational articles. This scale evaluates the articles in terms of the selection process (in four sections of definition of cases, introduction of cases, selection of controls and definition of controls), comparability (in one section includes: the comparability of cases and controls based on analysis design) and exposure/outcome (in three sections including: measurement of exposure/outcome, the same method of measuring exposure/outcome for cases and controls, and the degree of non-response to exposure/outcome (19). The scoring of the scale is like that if the items considered in the scale are mentioned, the number 1 is given and if not, the number 0 is assigned. The total scores assigned to the reported items are considered as the total quality score of the article. According to the Newcastle-Ottawa scale, the highest score that each article can get is 10 (the strongest study) and the lowest score is zero (the weakest study). In order to evaluate the quality, the articles that get a score lower than the average score (less than 4 points) were considered as low quality. Two authors, independently, collected the required data for the studies and recorded it in the checklist designed by the research team.

Extracted data from the articles included: first author's name, year of study publication, study location, study design, sample size, tools, results, and total quality score obtained from the Newcastle-Ottawa scale. After collecting the data, the extracted data was reviewed. If two researchers had different opinions about the data, the problem was referred to the senior researcher and the final decision was made by him. In the first stage, the process of qualitative synthesis of the extracted data was done for systematic review. Then, in order to perform quantitative data synthesis, the data extracted from the articles that were suitable for meta-analysis were entered in the Stata Version 14 software.

Considering that the investigated index was the relationship between Obesity and Overweight with Sexual Function, to combine the results of different studies, the mean and standard deviation and the standardized mean difference index were used. The I² index was used to check the heterogeneity between studies and in case of heterogeneity, the random effects method was used. The I2 index less than 0.25 indicates low, between 0.25-0.75 indicates moderate and greater than 0.75 indicated high heterogeneity. Sensitivity analysis was used to check the robustness of the results of meta-analysis, and Bagg's test was used to check the publication bias. In case of publication bias, Trim and Liff method was used to combine studies.P value less than 0.05 was considered significant.

Results

Through the initial search of databases, 1803 articles were first retrieved, after removing 1620 duplicate and unrelated articles, 183 articles were evaluated based on the inclusion criteria. Finally, after removing 168 articles, 15 full-text articles were included in the systematic review. 10 articles were excluded from entering the quantitative stage due to incomplete data reporting or not reporting of indicators required to enter the meta-analysis, and finally 5 articles entered the meta-analysis. The flow chart of the studies is shown in figure 1.

The characteristics of the studies included in the meta-analysis and their quality scores are shown in Table 2. All studies were cross-sectional and case-control. The publication year of the studies varied from 2007 to 2020. In all articles, 3 articles were published in Persian and 12 articles were published in English (Table 1).

The results of the meta-analysis of the studies of Mozafari et al. (2014) and Sponit et al. (2007) using the standardized mean difference effect size showed that there was heterogeneity between studies based on the I² index (I2=0.71). So, the random effects method was used to combine the studies and their final result of the study effects. Based on the results.

of the random effects method, there was no statistically significant difference between the two groups of cases (BMI <25) and controls (BMI <25), in terms of the average total score of sexual function (P = 0.081); So that the standardized mean difference between the two groups was estimated as -1.40 with a confidence interval (0.17, -2.97) (Figure 2).

In other words, there was no significant difference in the mean score of the total sexual function in the case and control groups. Also, based on the results of Bag test, there was no publication bias in the studies (P=0.317). The results of the meta-analysis of the studies, Faridi et al. (2013), Karimi et al. (2019), Fabion et al. (2020) using the standardized mean difference effect size, showed that there was heterogeneity between the studies based on the I² index.

 I²=0.57), so random effects method was used to combine the studies and the final result of the study effects. Based on the results of the random effects method, there was no statistically significant difference between the two groups of cases (BMI = 25-30) and controls (BMI < 25), in the total score of sexual function (P = 0.480); So that the standardized mean difference between the two groups was estimated as -0.07 with a confidence interval of (0.12, -0.26) (Figure 3).

In other words, there was no significant difference in the mean score of the total sexual function in the case and control groups. Also, based on the results of Bag test, there was no publication bias in the studies (P=0.602). The results of the meta-analysis of articles by Faridi et al.(2013), Karimi et al.(2020), Fabion et al.(2020) in the desire subscale using the standardized mean difference effect size showed that there is heterogeneity between studies based on the I² index (I2=0.10), So, the fixed effect method was used to combine the studies and the final result of the study effects. Based on the results of the fixed effect method, there was 

a statistically significant difference between the two groups (BMI = 25-30) and control (BMI < 25) (P = 0.003); The standardized mean difference between the two groups was estimated as -0.09 with a confidence interval of (-0.03, -0.15) (Figure 4).

The mean score of desire in the case and control groups had a significant difference and it was lower in the case group. Also, based on the results of Bag test, there was no publication bias in the studies (P=0.117). The results of the meta-analysis of the studies by Faridi et al. (2013), Karimi et al. (2019), Fabion et al. (2020) in the satisfaction subscale using the standardized mean difference effect size showed heterogeneity between the studies based on the I² index. (I2=0.10), Therefore, the fixed effect method was used to combine the studies and the final results of the study effects. Based on the results of the fixed effect method, there was a statistically significant difference between the two groups of cases (BMI = 25-30) and controls (BMI < 25) (P = 0.025); So that the standardized mean difference between the two groups was estimated as -0.07 with a confidence interval (-0.01, -0.13) (Figure 5).

Also, there was a significant difference in the mean satisfaction score between the case and control groups and it was lower in the case group. In addition, based on the results of Bag test, there was no publication bias in the studies (P=0.117). In other sub-scales, there was no statistically significant difference between the case and control groups (P<0.05) (Figure 6).

Discussion

The results of present systematic review and meta-analysis showed that obesity and overweight can cause a significant decrease in sexual desire and sexual satisfaction of obese and overweight women. Medical dieseas (such as cardiovascular disorders, diabetes, metabolic syndrome, polycystic ovary syndrome, etc.), change in the level of circulation of hormones that are affective in sexual responses and desire, change in a person's mental image of her body and negative self-concept are several mechanisms which can be potentially effective and can lead to sexual dysfunctions such as decreased sexual desire and satisfaction in obese and overweight women. A negative mental image of the body can lead to adverse psycho-social symptoms, such as anorexia or bulimia nervosa, depression, social anxiety, and sexual desire disorders (5, 6, 9).

Mozafari et al. (2015) showed in their study that obesity and overweight can lead to a decrease in sexual satisfaction in these women and affect their quality of life and sexual health. Obesity can reduce self-confidence and sexual satisfaction in women by creating negative self-image and unpleasant perceptions of body image in women (20). Also, Pace et al. (2010) in their study showed that women with obesity and overweight have a lower level of sexual satisfaction than women with normal weight (24). Raisi et al also showed that overweight women have less sexual satisfaction, sexual desire ) Libido)and orgasm(25). The study of Rostami et al. (2020) also showed that overweight and obesity in women with its effects on the increase of sex hormones and the risk of polycystic ovarian syndrome and causing unpleasant changes in a person's appearance, such as acne and excess hair, reduces the desirability of body image and leads to defects sexual function in these women (33). The results of the study by Karimi et al. (2019) showed that obesity and overweight can cause a decrease in sexual desire in women, disrupt women's marital relationships, and affect their quality of life (8).

It can be said that negative body image, low self-confidence, lack of interpersonal relationships, and feeling ashamed due to high weight are among the effective reasons for reducing sexual desire in obese women (14).In Bates et al.'s study (2019) they also showed a statistically significant relationship between obesity and overweight with decreased sexual desire, the most common disorder in this study was related to sexual desire and orgasm(15).

But Mozafari et al. (2015) did not show a statistically significant relationship between obesity and sexual desire in their study. In this study, psychological factors and interpersonal relationships were known to be more effective than body mass index and overweight on the sexual function of over weight and obese women, which is not agree with the results of the present study (20). The reason for this inconsistency can be considered the difference in the individual and social characteristics of people and the cultural extent between different societies.

The results of a study on women with hyperlipidemia showed that body mass index is independently related to sexual dysfunction and the scores of arousal, desire, slippery and satisfaction areas are lower than the group without hyperlipidemia (34). Also, in another study on women with metabolic syndrome (a set of common disorders associated with abdominal obesity), it was observed that the overall score of sexual function in women with this disease was lower than the control group, and the most statistically significant difference was in the areas of arousal, orgasm and satisfaction (35). Also, Fabion et al. (2020) showed in their study that overweight or obesity is associated with a decrease in sexual activity, and the decrease in sexual function in obese women has a statistically significant difference in areas such as sexual arousal, satisfaction, orgasm, and pain (22).

However, the underlying mechanism of obesity related to sexual dysfunction has not been clearly established. Previous studies show that psychological and social factors such as a person's perception of her body, depression, low self-confidence and negative self-image can have a negative effect on the self-esteem and sexual function of people. Also, the negative effects of co-morbidities in obese people, such as hypertension, diabetes, metabolic syndrome, etc., have been clearly proven on sexual dysfunctions (36). According to that women's sexual health is one of the priorities of the World Health Organization, and unfavorable sexual function can have a negative effect on women's sense of efficiency, worthiness and self-confidence, and it can increase the concern of couples about the stability and strength of their joint life, So special attention should be paid to the diseases and factors influencing the sexual desire, ability and function of people (37, 38).

Considering the importance of optimal sexual function in women, the significant prevalence of obesity and overweight and its clinical importance, it seems that surveing the sexual function of affected women, in order to know more about the dimensions of sexual dysfunction in these women and to adopt preventive measures such as education And early counseling about nutrition, physical activity, mental health, and lifestyle improvement is necessary to improve the quality of sexual life of these people (39). Because of that the previous studies on the relationship between obesity and sexual function are mostly narrative and systematic reviews, therefore, the meta-analysis of the present study is considered to be one of its advantages. In the present study, some articles were excluded from entering the meta-analysis stage due to the lack of a control group, incomplete reporting of results, or due to the lack of reporting of the mean and standard deviation of the total score of sexual function, which is one of the limitations of this study, Therefore, the conclusions from the present study should be considered carefully.

It is suggested that in future researches, interventional studies should be designed to reduce the occurrence of sexual dysfunction in obese and overweight women. In addition, the effective factors in the occurrence of sexual disorders in these women have been investigated separately, and strategies to reduce sexual disorders and their complications in this group of women have been proposed.

Conclusion

obesity and overweight can lead to a decrease in sexual desire and satisfaction in women, so policymakers and health care providers should identify this group of women in terms of the occurrence of sexual dysfunction and provide suitable interventions to improve the sexual function of this group of women.

Declarations

Acknowledgements

This study is the result of a research proposal that was approved by Mashhad University of Medical Sciences (code: 4020128). We hereby thank and appreciate The Vice president for Research of Mashhad University of Medical Sciences and also to all the researchers whose studies were used in this systematic review and meta-analysis study.

Conflicts of interest

Authors declared no conflicts of interest.

Ethical considerations and ethical approval

In order to comply with ethics in the research, the ethics code IR.MUMS.NURSE.REC.1402.044 was obtained from Mashhad University of Medical Sciences.

Funding

Not applicable.

Authors’ contribution

FZK Conceptualization and writing and review and editing GSA  writing, review and editing. MA and MRS Aanalysis, review and editing. All authors read and approved the final manuscript.