Metabolic and bariatric surgery (MBS), particularly sleeve gastrectomy, is established as the most effective long-term treatment for severe obesity, offering significant weight reduction, comorbidity resolution, and improved quality of life. Despite the similar prevalence of obesity between men and women, a persistent gender disparity exists in the utilization of bariatric surgery. Women account for approximately 80% of surgical candidates, while men are underrepresented at around 20%. This discrepancy may arise from behavioral differences such as healthcare-seeking patterns, body image perceptions, and self-referral tendencies. Furthermore, gender influences various obesity aspects including body composition, eating behaviors, and clinical presentation at the time of surgery.

Existing literature on gender-specific weight loss outcomes after bariatric surgery remains inconclusive. Some studies suggest men lose more absolute weight while women achieve greater relative reductions in body mass index (BMI) or percentage of excess weight loss, but these findings vary depending on population characteristics and methodologies. Notably, there is a scarcity of recent data from Mediterranean populations, especially under updated clinical protocols emphasizing multidisciplinary care.

This prospective observational study aimed to evaluate gender differences in weight loss outcomes following sleeve gastrectomy in an Italian cohort managed under current multidisciplinary protocols. A total of 131 patients (109 females and 22 males) underwent sleeve gastrectomy at the IRCCS Istituto Auxologico Italiano, Milan. Patients were carefully selected following the SICOB 2023 guidelines and underwent standardized preoperative education and postoperative care involving nutritional, psychological, and medical support.

Anthropometric measures (weight, BMI, waist circumference), metabolic parameters, and comorbidities were assessed at baseline and 12 months post-surgery. Outcomes included absolute weight loss, total weight loss percentage (TWL%), excess weight loss percentage (EWL%), and waist circumference reduction. Statistical analyses included t-tests, chi-square tests, and multivariate linear regression adjusted for baseline BMI and age.

The cohort’s mean age was approximately 45.5 years, with no significant difference between genders. Men had a significantly higher baseline body weight (134.8 kg vs. 109.4 kg) and waist circumference (134.3 cm vs. 118.9 cm) compared to women. Despite this, BMI was comparable between sexes (~42 kg/m²). The prevalence of type 2 diabetes and hypertension did not significantly differ, though men showed a tendency toward higher fasting glucose and hypertension rates, consistent with a heavier metabolic burden at baseline.

At 12 months post-surgery, the entire cohort experienced a significant mean weight loss of 34.3 kg (p < 0.001). Men lost significantly more absolute weight than women (36.6 kg vs. 31.2 kg; mean difference 5.39 kg, p = 0.028), with a moderate effect size (Cohen’s d = 0.52). However, relative weight loss measures such as TWL% and EWL% did not differ significantly by gender (TWL%: 27.2% men vs. 28.6% women, p = 0.48; EWL%: 45.9% men vs. 48.4% women, p = 0.46). Waist circumference reduction was also similar between sexes, indicating comparable improvements in central adiposity.

When analyzing categorical weight loss thresholds, 45% of patients reached ≥30% TWL%, with a higher but non-significant proportion among women (47.7% vs. 31.8%, p = 0.172). Distribution across other weight loss brackets was also comparable.

Multivariate linear regression revealed that age, gender, and baseline BMI significantly predicted absolute weight loss at 12 months. Men were predicted to lose an additional 5.89 kg compared to women after adjusting for age and BMI (p = 0.008). In contrast, when predicting relative weight loss (TWL%), only age remained significant, and gender was not a significant predictor (p = 0.653). These results suggest that physiological differences such as body composition and metabolic rate partly explain the greater absolute weight loss observed in men but do not impact proportional weight loss.

The study confirms that sleeve gastrectomy is effective for substantial weight and waist circumference reduction in both men and women. Although men lose more weight in absolute terms, relative weight loss and central adiposity improvements are comparable between sexes. These findings align with prior research indicating men’s larger absolute losses are likely due to higher baseline body weight, while women achieve similar or slightly better relative reductions.

The similar waist circumference reduction between genders suggests equal efficacy in reducing visceral fat, an important factor for metabolic risk improvement. The persistent gender disparity in MBS utilization, with men underrepresented despite heavier metabolic burdens, is concerning and likely reflects delayed referral and healthcare access barriers.

Behavioral and psychological factors may also contribute to observed patterns. Women are more prone to emotional eating, which can hinder dietary adherence, while men may exhibit external eating behaviors. The multidisciplinary postoperative care, including nutritional and psychological support, may have mitigated these behavioral differences, leading to comparable outcomes.

A key strength of this study is its adherence to updated clinical guidelines, including rigorous, multidisciplinary perioperative protocols that reflect current best practices. Frequent nutritional counseling and psychological support likely enhanced adherence and weight loss maintenance.

However, important limitations include the gender imbalance with men making up only 17% of the cohort, limiting statistical power and generalizability. Referral bias with men presenting later and with greater comorbidities may have influenced baseline characteristics and outcomes. The absence of psychological and dietary adherence data restricts understanding of behavioral influences on weight loss. Longer follow-up and inclusion of behavioral assessments are warranted to elucidate gender-specific trajectories and optimize personalized care.

This study demonstrates that both men and women benefit substantially from sleeve gastrectomy under modern multidisciplinary protocols. Although men lose more weight in absolute terms, relative weight loss and reductions in central adiposity are similar across genders. The findings emphasize the need for equitable, early access to bariatric surgery for men and women, coupled with personalized support to maximize long-term success and health improvements.

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