This review has successfully evaluated the impact of weight loss programs on UI symptoms in patients with OAB. It included a total of ten clinical studies, comprising seven prospective cohorts, one retrospective cohort, and two randomized clinical trials. Standard therapy for OAB typically involves lifestyle modifications and the use of antimuscarinic medications. However, there is currently no specific guideline that exclusively recommends weight loss programs as a method to improve UI symptoms in OAB patients (
29).
It has been previously explained that the pathogenesis of UI involves increased intra-abdominal pressure, which is typically higher in obese or overweight individuals compared to those of normal weight (
7). Overweight OAB patients have also been reported to experience lower health-related quality of life (HRQOL) compared to those of normal weight (
30).
Various approaches are employed in weight loss programs. Ultimately, patient comfort and compliance with these programs are crucial factors to consider, as they often need to be sustained over the long term. Weight loss programs that include a low-calorie intake (around 800 kcal/day), regular physical activity, and modifications to eating and exercise habits have been shown to positively impact UI (
25).
For example, Hagovska, et al. (
6) conducted a study involving 70 OAB women with an average age of 26.4 years and reported a decrease in BMI among patients who underwent a weight loss program by the third month. This reduction in BMI was followed by a decrease in SUI symptoms experienced by the patients. The program included exercises targeting deep abdominal muscles (transversus abdominis, obliquus abdominis internus) and strengthening superficial abdominal muscles (obliquus abdominis externus, rectus abdominis), along with aerobic activity.
A study by Subak, et al. (
18) reported that behavioral weight loss programs were effective in decreasing the symptoms of UI. The number of weekly UI episodes decreased by 70% within 6 months after the intervention, with the greatest decrease observed in the frequency of stress-incontinence episodes (
18).
Whitcomb and Subak (
20) reported a clear dose-response effect of weight on UI, with each 5-unit increase in BMI associated with a 20% - 70% increase in the risk of UI. The maximum effect of weight on UI has an odds ratio of 4 - 5. Additionally, the odds of developing UI over 5 - 10 years increase by approximately 30% - 60% for each 5-unit increase in BMI. There appears to be a stronger association between increasing weight and both prevalent and incident stress incontinence (including mixed incontinence) compared to urge incontinence.
Weight loss studies indicate that both surgical and nonsurgical approaches lead to significant improvements in the prevalence, frequency, and symptoms of UI. Clinicians should recognize the importance of managing BMI through various body weight reduction methods. Uncontrolled increases in BMI, which can lead to metabolic syndrome (MetS), have been shown to heighten the risks and exacerbate the condition of OAB.
Metabolic syndrome can elevate the metabolic rate in bladder tissue, playing a crucial role in mechano-sensory transduction (
31). This is facilitated by increased mechanical load, which activates sensory afferents in the bladder, leading to heightened oxidative stress, systemic inflammation, and insulin resistance (
31). These factors contribute to chronic pelvic ischemia and urothelial dysfunction. Additionally, a higher BMI may trigger mechanical factors associated with increased intra-abdominal and intravesical pressure (
32).
Neuroendocrine processes, triggered by leptin secretion and inflammatory cytokines from visceral adipose tissue, may initiate noradrenergic sympathetic activity and cause urothelial irritation (
32). Moreover, obesity can lead to insulin resistance, adversely affecting lipid ratios by reducing HDL cholesterol and increasing triglyceride and LDL cholesterol levels in the bloodstream. These unfavorable cholesterol ratios may contribute to the accumulation of atheromatous deposits in the bladder wall, precipitating bladder wall ischemia, urothelial dysfunction, and an increased risk of OAB (
31).
While a gradual decrease in BMI was associated with a reduction in SUI symptoms, the dropout rate during the intervention was high at 26%, partly due to adherence issues with the exercise program (
6). Another study with a longer observation period in the lifestyle intervention and weight loss group reported an improvement in UI symptoms. However, at the 18-month follow-up, the difference between the groups in total episodes and SUI was no longer significant due to weight regain (
33,
34). It is important to note that lifestyle and dietary interventions alone may not be sufficient to achieve and maintain adequate weight loss in obese women with multiple comorbidities (
21).
The advancement of medical technology has facilitated elective surgeries that can significantly reduce patients' weight. One such procedure is bariatric surgery, particularly gastrectomy, which is popular and has proven effective in achieving weight loss (
16). However, surgery is usually performed in patients with a BMI > 40 or BMI > 35 with diabetes (
35). There are two types of bariatric surgery: Laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (RYGB). In LSG, the lower part of the stomach is removed, resulting in a smaller stomach that limits food intake. After the surgery, patients eat smaller portions due to the reduced stomach size. In contrast, RYGB modifies the transit of food along the gastrointestinal tract by rerouting the passage between the stomach and small intestine. This procedure alters the absorption capacity of food, as the proximal portion of the small intestine is bypassed. Both techniques are effective options that have been proven to aid in significant weight loss (
36).
Palleschi, et al. (
19) reported that symptoms of OAB were common in the morbidly obese cohort, affecting more women than men. Compared with untreated patients, patients treated with LSG had significantly reduced BMI 180 days postoperatively; this outcome was associated with improvement in OAB symptoms, whereas no change occurred in untreated controls.
Ait Said, et al. (
23) confirmed that weight loss after bariatric surgery improves SUI, Urge Incontinence, dysuria, and quality of life.
Anglim, et al. (
21) reported postoperative cure rates of 41% for SUI, 38% for OAB, and 48% for mixed incontinence, with 44% of women experiencing complete resolution of their symptoms. The use of postoperative sanitary napkins decreased dramatically from 61% to 36% (P < 0.01). The study also documented a significant improvement in the quality of life of women with OAB, as evidenced by a decrease of 4.8 (5) in the ICIQ-UI SF score, from 9.3 (4.4) preoperatively to 4.5 (5) postoperatively.
Kim, et al. (
24) reported that at a 1-year postoperative follow-up after laparoscopic gastric bypass-type bariatric surgery, there were significant improvements in voiding status as assessed by several standard urologic voiding questionnaires/indices.
Waeckel et al. (
17) also reported that bariatric surgery seems to be effective at treating SUI and OAB, with long-lasting effects still noted at 6 years.
In a cohort study conducted in 2013 involving 100 Roux-en-Y gastric bypass patients, an average reduction of 10 kg/m² in BMI was observed, with resolution rates of 84% for UI symptoms, 85% for fecal incontinence, and 74% for pelvic organ prolapse (POP) (
37).
Furthermore, Ranashinghe, et al. (
38) found significant improvement in women assessed using the International Consultation on Incontinence Questionnaire short-form score (P = 0.0008) and quality of life scores (QOL; P < 0.0001). In women, each kilogram of weight loss resulted in an increase of 0.05 in the short-form Incontinence Questionnaire score (P = 0.03).
Other studies have also reported improvements in various comorbidities related to pelvic floor disorders following bariatric surgery. In a study involving 98 women with SUI, OAB, and anal incontinence, symptom resolution was observed in 11 out of 23 (48%) women with SUI, 8 out of 11 (73%) women with OAB, and 4 out of 20 (20%) women with anal incontinence after 12 months of follow-up (
39). This suggests that while bariatric interventions can significantly improve some pelvic floor disorders exacerbated by increased intra-abdominal pressure, they may not fully resolve all conditions.
Scozzari, et al. (
40) also reported that improvement was limited to UI symptoms, with no significant changes in anorectal function and an increase in flatus incontinence. Despite significantly reducing intra-abdominal pressure, it remains unclear why conditions directly influenced by this pressure do not always improve with bariatric interventions.
Thus, while bariatric procedures lead to weight reduction over time, they also involve other mechanisms that may contribute to the improvement of UI symptoms.
Ranasinghe, et al. (
38) and Wesnes (
41) suggest that the role of decreased BMI in improving UI symptoms is not solely due to its effect on bladder pressure. O'Boyle, et al. (
16) reported that there was no correlation between higher BMI and the rate of weight reduction in terms of the duration and severity of symptoms.
There are other factors that influence the relationship between decreased BMI and bladder pressure. One contributing factor to symptom improvement is the reduction in fluid intake during the early postoperative period. Patients often struggle to meet the recommended minimum fluid intake of 1.5 liters per day in this phase. This aligns with guidelines for fluid intake in behavior change therapy for UI patients.
However, there are no explicit studies assessing the differences in fluid intake and output in patients undergoing bariatric interventions.
In addition to the natural fluid restriction that occurs after bariatric surgery, there is also a decrease in the amount of adipose tissue that produces leptin in the bloodstream. Leptin influences the autonomic nervous system, particularly the noradrenergic sympathetic nerves, which play a role in the pathophysiology of incontinence (
42).
Despite the satisfactory results, bariatric surgery is associated with several complications, including persistent nausea and vomiting, intolerance to solid food, and severe dumping syndrome (
43). A multicenter study in India involving over 10,000 patients reported a complication rate of 3.13% for bariatric surgery (n = 363), which is consistent with findings reported by Melissas, et al. of 2.1% to 3% (
44,
45). The mortality rate associated with this procedure ranges from 0.16% to 0.22% (
46).
Daigle, et al. (
47) identified bleeding and leakage as the complications with the most significant overall impact, leading to organ failure, reoperation, and admission to the intensive care unit following bariatric surgery. Therefore, the decision to proceed with bariatric surgery should consider the patient's comprehensive risk of morbidity and mortality.
This review demonstrates that effective weight loss strategies often involve a combination of dietary changes, exercise, and, in some cases, bariatric surgery. Programs integrating low-calorie intake and physical activity have shown improvements in UI symptoms. Bariatric surgery, particularly Laparoscopic Sleeve Gastrectomy and Roux-en-Y Gastric Bypass, has also demonstrated substantial benefits in reducing UI symptoms and improving quality of life. However, invasive procedures carry several complications, and not all obese patients are suitable candidates for these interventions.
Unfortunately, the precise mechanisms underlying the association between obesity and incontinence remain unclear, and additional neurophysiological and urodynamic studies are needed to better define the obesity–UI relationship.
It is also important to acknowledge several limitations of the included studies. This review encompasses studies with unstandardized outcome measures and varying approaches to weight loss programs. Current data are limited by both short-term follow-up and unexplained heterogeneity among studies. Finally, it is crucial to note that some of the clinical studies mentioned are retrospective studies based on prospective cohorts, which introduce inherent biases in the study design.
5.1. Conclusions
Evidence from multiple clinical studies supports that weight loss programs are effective in reducing UI symptoms in patients with OAB, whether through surgical or non-surgical procedures. While lifestyle interventions focusing on calorie reduction and physical activity have shown promising results, bariatric procedures such as Laparoscopic Sleeve Gastrectomy and Roux-en-Y Gastric Bypass provide significant weight reduction and symptom relief for morbidly obese patients.
Clinicians should consider individualized approaches to weight management, taking into account the potential complications of surgical interventions and the importance of maintaining long-term weight loss for optimal patient outcomes.
Recommendations for future research should aim to better understand the underlying mechanisms linking obesity and UI; use standardized outcome measures to facilitate comparisons between studies; and include literature with RCT designs to reduce bias and enhance the validity of results. Additionally, it is crucial to investigate factors that may explain the heterogeneity observed among existing studies.