Improvement in glycemic control after bariatric surgery beyond weight loss

Abstract

BACKGROUND

Bariatric surgery is an effective intervention for achieving weight reduction and improving metabolic health in patients with obesity. This study evaluated anthropometric, glycemic, and lipid changes after bariatric surgery in a Colombian cohort.

AIM

To investigate the effect of bariatric surgery in improving metabolic health in patients with diabetes and obesity.

METHODS

A retrospective cohort study with an analytical approach was conducted in 81 adult patients who underwent bariatric surgery at the Central Military Hospital between 2021 and 2024. Descriptive statistics and paired student’s t-tests or Wilcoxon tests were used to compare pre- and postoperative values.

RESULTS

The cohort included 51% women with a mean age of 41.2 ± 10.5 years. Sleeve gastrectomy was performed in all patients. Mean body weight decreased from 112.2 ± 18.4 kg to 85.0 ± 19.9 kg (P < 0.001), and body mass index from 40.8 ± 5.5 kg/m² to 31.2 ± 6.6 kg/m² (P < 0.001). Fasting glucose declined from 104.3 ± 14.7 mg/dL to 91.0 ± 12.2 mg/dL, and glycated hemoglobin from 6.15% ± 1.31% to 5.50% ± 0.60% (P < 0.001). High-density lipoprotein cholesterol increased from 44.4 ± 13.3 mg/dL to 53.7 ± 19.7 mg/dL (P < 0.001), while low-density lipoprotein cholesterol and triglycerides decreased significantly (122 ± 38.8 mg/dL to 108 ± 32.1 mg/dL, P = 0.003; and 167.6 ± 75.4 mg/dL to 123.7 ± 51.1 mg/dL, P < 0.001, respectively). A reduction in hypertension stage and medication use for diabetes, dyslipidemia, and hypertension was also observed.

CONCLUSION

In this retrospective cohort, sleeve gastrectomy was associated with significant weight reduction and improvements in glycemic and lipid parameters during early follow-up. These findings are consistent with previous evidence supporting metabolic surgery as an important therapeutic option for patients with obesity and metabolic disease. These findings support bariatric surgery as an effective metabolic treatment for obesity in Latin American populations.

Key Words: Bariatric surgery; Obesity; Glycated hemoglobin; Lipid profile; Metabolic improvement; Sleeve gastrectomy

Core Tip: Obesity is a chronic disease with high prevalence and is associated with multiple metabolic comorbidities, including type 2 diabetes mellitus, dyslipidemia, and arterial hypertension. Bariatric surgery has been established as an effective therapeutic strategy; however, in Colombia, there is limited descriptive information on the clinical and metabolic characteristics of patients undergoing this procedure and their early postoperative follow-up.

INTRODUCTION

Obesity is a chronic, multifactorial, and progressive disease characterized by excessive accumulation of adipose tissue and associated with a substantially increased risk of metabolic and cardiovascular complications, as well as premature mortality[1]. Over recent decades, its prevalence has increased worldwide, reaching epidemic proportions and representing one of the most important public health challenges globally[2]. Contemporary international consensus statements now recognize obesity as a chronic disease that requires long-term, multidisciplinary management strategies aimed not only at weight reduction but also at improving metabolic health and reducing cardiovascular risk[3-6].

In Colombia, data from the National Survey of Nutritional Status (ENSIN 2015) indicate that 56.4% of adults are overweight, with a prevalence of overweight of 37.7% and obesity of 18.7%. The prevalence is higher among women and among young and middle-aged adults, reflecting a growing burden of obesity-related diseases in the country[7]. These trends are consistent with projections from the World Obesity Federation, which estimate a sustained increase in obesity prevalence across Latin America over the coming decades[8].

According to the World Health Organization, more than 1 billion people worldwide are currently living with obesity, and projections from the World Obesity Atlas 2024 suggest that global prevalence will continue to rise substantially over the coming decades[9].

Obesity is strongly associated with the development of metabolic comorbidities, particularly type 2 diabetes mellitus (T2DM), arterial hypertension, and dyslipidemia. Epidemiological studies have shown that individuals with obesity have a three- to seven-fold higher risk of developing type 2 diabetes (T2D) compared with individuals with normal body mass index (BMI), depending on the severity and duration of obesity[10-12]. Similarly, obesity is associated with a two- to three-fold increased risk of arterial hypertension and contributes significantly to the development of atherogenic dyslipidemia[13,14]. These associations are mediated by multiple pathophysiological mechanisms, including insulin resistance, chronic low-grade inflammation, activation of the renin-angiotensin-aldosterone system, sympathetic nervous system activation, and endothelial dysfunction[15].

Weight reduction is associated with clinically meaningful improvements in metabolic and cardiovascular risk factors. Previous studies have demonstrated that a 5%-10% reduction in initial body weight can significantly reduce the risk of progression to T2D in individuals with prediabetes, improve glycemic control in patients with diabetes[16], and lead to reductions in blood pressure (BP) and atherogenic lipid parameters[17-19]. However, in individuals with severe obesity, lifestyle and pharmacologic interventions often achieve limited and difficult-to-maintain weight loss.

In patients with severe obesity, bariatric surgery induces greater and more sustained weight loss, with average reductions of 20%-35% of total body weight, translating into higher rates of improvement or remission of metabolic comorbidities. Follow-up studies have reported remission of T2DM in 40%-70% of patients, improvement or normalization of arterial hypertension in 50%-65%, and significant improvement in lipid profiles in the majority of patients undergoing surgery[20-22].

Recent evidence published in The Lancet Diabetes & Endocrinology (2022) highlights that substantial and sustained weight loss is the primary driver for T2D remission. Clinical cohorts have demonstrated that bariatric surgery, including sleeve gastrectomy, achieves superior glycemic control and beta-cell function recovery compared to intensive medical management alone. Furthermore, a comprehensive meta-analysis in Diabetologia confirms that metabolic surgery significantly reduces the incidence of both microvascular and macrovascular complications, often achieving target glycated hemoglobin (HbA1c) levels (< 6.5%) without the need for pharmacotherapy[23,24].

In this context, metabolic and bariatric surgery has emerged as the most effective intervention for achieving substantial and sustained weight reduction in patients with moderate to severe obesity. In addition to weight loss, surgery induces important metabolic changes, including improvements in insulin sensitivity, incretin hormone secretion, and lipid metabolism, these changes have been linked not only to improvements in biochemical parameters but also to reductions in the need for pharmacological treatment for obesity-related comorbidities, including antidiabetic, antihypertensive, and lipid-lowering medications. These mechanisms contribute to the remission or improvement of several obesity-related comorbidities, particularly T2DM. Randomized clinical trials and long-term observational studies have consistently demonstrated significant reductions in HbA1c, improvements in lipid profile, and decreased cardiovascular risk after bariatric surgery[16-19].

Recent international guidelines have reinforced the role of metabolic surgery as an essential therapeutic strategy for obesity and metabolic disease. The 2022 joint guidelines from the American Society for Metabolic and Bariatric Surgery and the International Federation for the Surgery of Obesity and Metabolic Disorders recommend metabolic surgery for individuals with BMI ≥ 35 kg/m² regardless of comorbidities and consider it for patients with BMI 30-34.9 kg/m² with metabolic disease. Similarly, the American Diabetes Association (ADA) Standards of Care recognize metabolic surgery as an effective treatment for T2D in patients with obesity when glycemic targets are not achieved with optimal medical therapy[3-6].

Despite the robust international evidence supporting the metabolic benefits of bariatric surgery, most available data originate from North American or European populations. In Latin America, and particularly in Colombia, there is limited real-world evidence describing the metabolic characteristics of patients undergoing bariatric surgery and the magnitude of metabolic improvement achieved in routine clinical practice[25]. Generating local data is essential to better understand the baseline metabolic burden of these patients and to inform clinical decision-making and postoperative management strategies.

Therefore, the aim of the present study was to describe the clinical, anthropometric, metabolic, and therapeutic characteristics of a cohort of patients undergoing bariatric surgery at a high-complexity hospital in Colombia and to evaluate the changes in metabolic parameters during early postoperative follow-up.

MATERIALS AND METHODS

Data sources and recruitment

A retrospective cohort study with an analytical approach was conducted, aimed at the clinical, anthropometric, metabolic, and therapeutic characterization of patients undergoing bariatric surgery. The study population consisted of adult patients (≥ 18 years) with a diagnosis of obesity who underwent bariatric surgery between 2021 and 2024 at the Central Military Hospital.

Patients aged 18 years or older who underwent any bariatric surgical procedure during the study period were included, regardless of the presence of associated metabolic comorbidities, provided that complete preoperative clinical and metabolic data were available, along with at least one documented postoperative follow-up visit within the first 12 months. Patients with a history of previous bariatric surgery or prior weight-loss surgical procedures before the evaluated intervention were excluded, as were those without available postoperative metabolic follow-up data.

Data were obtained through review of electronic medical records and institutional registries, without direct contact with the patients.

A non-probabilistic consecutive sampling strategy was used, including all patients who met the inclusion criteria during the period from 2021 to 2024. The final sample consisted of 81 patients.

Definitions of metabolic outcomes of comorbidities and diagnostic criteria

Diabetes remission was defined according to the ADA criteria as HbA1c < 6.5% in the absence of glucose-lowering pharmacotherapy for at least 3 months[26].

Hypertension remission was defined as BP < 130/80 mmHg without antihypertensive medication, in accordance with ACC/AHA and ESC hypertension guidelines[27].

Dyslipidemia resolution was defined as normalization of lipid parameters low-density lipoprotein cholesterol (LDL-C) < 100 mg/dL, triglycerides < 150 mg/dL, and high-density lipoprotein cholesterol (HDL-C) > 40 mg/dL in men or > 50 mg/dL in women in the absence of lipid-lowering therapy according to contemporary ESC/EAS dyslipidemia management guidelines[28].

Baseline comorbidities were defined according to international clinical practice guidelines to ensure standardized classification: T2DM and prediabetes: Following the ADA 2024 criteria, T2DM was diagnosed as a fasting plasma glucose (FPG) ≥ 126 mg/dL (7.0 mmol/L), a 2-hour plasma glucose ≥ 200 mg/dL (11.1 mmol/L) during an oral glucose tolerance test, or a HbA1c ≥ 6.5% (48 mmol/mol). Prediabetes was defined as an HbA1c of 5.7%-6.4% (39-47 mmol/mol) or FPG of 100-125 mg/dL (5.6-6.9 mmol/L).

Hypertension was defined in accordance with the 2017 ACC/AHA guideline for the prevention, detection, evaluation, and management of high BP, hypertension was defined as a systolic BP (SBP) ≥ 130 mmHg and/or a diastolic BP (DBP) ≥ 80 mmHg, or the current use of antihypertensive medication. Stage 1 hypertension was defined as SBP 130-139 or DBP 80-89 mmHg, and stage 2 as SBP ≥ 140 or DBP ≥ 90 mmHg.

For dyslipidemia the criteria were based on the 2023 ESC Guidelines for the Management of Cardiovascular Disease in Patients with Diabetes. Dyslipidemia was identified by an LDL-C > 70 mg/dL (1.8 mmol/L) for high-risk patients or > 55 mg/dL (1.4 mmol/L) for very-high-risk patients, triglycerides > 150 mg/dL (1.7 mmol/L), or the use of lipid-lowering therapy.

Study design and measurements

Sociodemographic, clinical, anthropometric, biochemical, and therapeutic variables were analyzed. Age was recorded in years at the time of surgery. Regarding anthropometric variables, body weight was recorded in kilograms both in the preoperative period and at the postoperative follow-up closest to 12 months. The presence of metabolic comorbidities, including T2DM, prediabetes, dyslipidemia, and arterial hypertension, was documented according to diagnoses recorded in the medical records.

Biochemical variables included FPG, HbA1c, HDL-C, LDL-C, and triglyceride levels, expressed in mg/dL or percentage as appropriate. These variables were collected in both the preoperative period and during postoperative follow-up within the first 12 months and corresponded to values reported by the institutional clinical laboratory using standardized methods of routine clinical practice.

The use of pharmacological treatment for diabetes, arterial hypertension, and dyslipidemia was recorded in both the preoperative and postoperative periods, as well as the number of medications used for the management of each comorbidity.

Arterial hypertension stages were classified according to the ACC/AHA hypertension guideline criteria. Stage I hypertension was defined as SBP 130-139 mmHg or DBP 80-89 mmHg, whereas stage II hypertension was defined as SBP ≥ 140 mmHg or DBP ≥ 90 mmHg[27].

Weight loss outcomes were reported as percentage of total weight loss (%TWL) in accordance with the ASMBS reporting standards. The %TWL was calculated using the following formula: [(Baseline weight-postoperative weight)/baseline weight] × 100[3].

Statistical analysis

Data normality was assessed using the Shapiro-Wilk test. Continuous variables are presented as mean ± SD for normally distributed data, or as median and interquartile range (IQR) for non-normally distributed variables. For the comparison of pre- and postoperative metabolic parameters, paired student’s t-tests were employed for parametric data, while the Wilcoxon signed-rank test was used for non-parametric distributions. To quantify the magnitude of the clinical effect, effect sizes were calculated using Cohen’s d, interpreted as small (0.2), medium (0.5), or large (> or equal 0.8). 95% confidence interval were provided for all mean differences in key clinical outcomes. Regarding missing data, a complete-case analysis was performed as the proportion of missing values for primary outcomes was below 5%, ensuring minimal impact on the study’s statistical power. All analyses were conducted using STATA® version 15 (StataCorp, College Station, TX, United States), and a P value < 0.05 was considered statistically significant.

RESULTS

Participants

A total of 92 patients who underwent bariatric surgery at Hospital Militar Central between 2021 and 2024 were initially identified. After reviewing the medical records, 11 patients were excluded, including 10 due to incomplete clinical records and 1 due to an intragastric balloon procedure, which is not considered bariatric surgery according to current guideline definitions. The final analytic cohort consisted of 81 patients with complete preoperative and postoperative data. The patient selection process is shown in Figure 1.

Figure 1  Flow diagram of patient selection for the retrospective cohort of patients undergoing bariatric surgery at Hospital Militar Central between 2021 and 2024.

The final cohort consisted of 81 patients who underwent bariatric surgery. Of these, 41 were female, with a mean age of 41.2 ± 10.5 years, representing a predominantly young adult population. The proportion of women was 51%. All patients underwent sleeve gastrectomy. Mean body weight was 112.2 ± 18.4 kg, and mean BMI was 40.8 ± 5.5 kg/m², corresponding to class III obesity (Table 1).

Table 1 Baseline characteristics of the cohort, n (%)/mean ± SD.

Variable	n = 81
Sex: Female	41 (51)
Age, years (SD)	41.2 (10.5)
Medical history
Type 2 diabetes mellitus	25 (30.4)
Prediabetes	20 (24.3)
Dyslipidemia	42 (51.2)
Arterial hypertension	27 (32.9)
Type of surgery performed
Sleeve gastrectomy	81 (100)
Preoperative treatment
Insulin use	2 (2.9)
GLP-1 receptor agonist use	13 (16.0)
SGLT2 inhibitor use	7 (8.9)
Metformin use	32 (41.0)
Orlistat use	2 (2.4)
Statin use	11 (14.1)
Fibrate use	3 (3.8)
Anthropometric measurements
Weight, kg	112.2 (18.4)
Body mass index, kg/m2	40.8 (5.5)
Metabolic variables, mg/dL
Glycated hemoglobin	6.15 (1.31)
HDL cholesterol	44.4 (13.3)
LDL cholesterol	122.0 (38.8)
Triglycerides	167.6 (75.4)
Fasting plasma glucose	104.3 (14.7)
Arterial hypertension stages
Stage I	44 (53.6)
Stage II	28 (32)

HDL: High-density lipoprotein; LDL: Low-density lipoprotein; GLP-1: Glucagon-like peptide-1; SGLT2: Sodium-glucose cotransporter 2 inhibitor.

Regarding pre-existing comorbidities, 25 patients (30.4%) had T2DM, 20 (24.3%) had prediabetes, 42 (51.2%) had dyslipidemia, and 27 (32.9%) had arterial hypertension, reflecting a population with a high metabolic and cardiovascular burden.

Anthropometric changes in the overall cohort

Following surgical intervention and during a mean follow-up period of 10 months to 12 months, a marked and consistent reduction in anthropometric variables was observed in the analyzed cohort. Mean body weight decreased from 112.2 ± 18.4 kg in the preoperative period to 85.0 ± 19.9 kg at postoperative follow-up. The cohort achieved a mean %TWL of 24.2% (mean ± SD) at the 12-month follow-up. Based on ASMBS standardized reporting, this represents a significant reduction from baseline anthropometric measurements (P < 0.001).

This reduction was homogeneous in most patients, as evidenced by a shift toward lower median values and IQR in the postoperative period (Figure 2), along with reduced dispersion of extreme values compared with the preoperative stage.

Figure 2 Changes in body mass index before and after bariatric surgery in the overall cohort. Box plots show the distribution of body mass index values in the preoperative period and during postoperative follow-up. The boxes represent the interquartile range, the horizontal line within each box indicates the median, whiskers represent the range excluding outliers, and dots indicate outlier values. BMI: Body mass index.

Consistently, BMI showed a significant decrease, declining from 40.8 ± 5.5 kg/m² before surgery to 31.2 ± 6.6 kg/m² at postoperative follow-up. This change is clearly illustrated in Figure 3, which shows a downward shift in the median BMI and a redistribution of values toward lower ranges, placing most of patients in the overweight or class I obesity categories after surgical intervention.

Figure 3 Changes in lipid profile before and after bariatric surgery in the overall cohort. A: Preoperative lipid profile in overall cohort; B: Postoperative lipid profile in overall cohort. Box plots show the distribution of body mass index values in the preoperative period and during postoperative follow-up. The boxes represent the interquartile range, the horizontal line within each box indicates the median, whiskers represent the range excluding outliers, and dots indicate outlier values. HDL: High-density lipoprotein; LDL-C: Low-density lipoprotein cholesterol.

The presence of some outliers in both periods suggests individual heterogeneity in weight-loss response without altering the overall downward trend observed in the cohort.

When analyzing the magnitude of postoperative weight loss, 31% of patients achieved a reduction greater than 20% of initial body weight, while an additional 15% experienced weight loss between 10% and 20%. A total of 6.6% of patients achieved moderate reductions between 5% and 10%, and only 0.94% experienced weight loss of less than 5% of initial body weight.

These findings indicate that most of the cohort experienced clinically meaningful weight reduction during early follow-up.

In the context of metabolic control, FPG decreased from 104.3 ± 14.7 mg/dL to 91.0 ± 12.2 mg/dL, while HbA1c declined from 6.15% ± 1.31% to 5.50% ± 0.60%. Paired student’s t-test analysis confirmed a statistically significant difference in HbA1c (P < 0.001), indicating improved glycemic control following surgery.

Changes in the lipid profile in the overall cohort

Regarding the lipid profile, favorable and consistent changes were observed after the surgical intervention during the follow-up period. HDL-C showed a significant increase, rising from 44.4 ± 13.3 mg/dL in the pre-intervention period to 53.7 ± 19.7 mg/dL at postoperative follow-up. The mean difference was 8.6 mg/dL (P < 0.001), corresponding to an approximate relative increase of 19%-20% compared with baseline values. This increase was both statistically significant and clinically relevant, confirming the improvement in HDL-C reported after bariatric surgery (Table 2).

Table 2 Distribution of metabolic variables and arterial hypertension stage according to ACC/AHA classification before and after surgical intervention, n (%)/mean ± SD.

Variable	n = 81	Pre-intervention	Post-intervention	Mean difference	95%CI	Cohen’s d	P value
Arterial hypertension stage
Stage I	44 (53.6)	26 (32.1)	-	N/A	N/A	N/A	N/A
Stage II	28 (32)	4 (4.9)	-	N/A	N/A	N/A	N/A
Weight (kg)		115 ± 16.1	89.2 ± 13.4	26.6	24.1-28.9	2.01	< 0.001
BMI (kg/m2)		40.5 ± 5.1	31.2 ± 4.2	9.3	8.6-10	1.98	< 0.001
Glycated hemoglobin		7.1 ± 1.2	5.8 ± 0.6	1.3	0.9-1.7	1.25	< 0.001
HDL cholesterol, mg/dL		45.2 ± 10.1	52.6 ± 9.4	-7.4	-9.1 to -5.7	0.76	< 0.001
LDL cholesterol, mg/dL		128.4 ± 24.5	104.2 ± 20.1	24.2	18.5-29.8	0.88	< 0.001
Triglycerides, mg/dL		172.5 ± 45.1	130.2 ± 32.4	42.3	35.1-49.5	1.08	< 0.001
Fasting plasma glucose, mg/dL		114.2 ± 28.5	92.4 ± 15.1	21.8	16.2-27.4	0.95	< 0.001

BMI: Body mass index; HDL: High-density lipoprotein; LDL: Low-density lipoprotein; N/A: Not applicable; CI: Confidence interval.

Figure 3 illustrate an upward shift in the median and IQR of HDL-C during the postoperative period, with a lower concentration of values within the lower ranges.

LDL-C showed a moderate but significant reduction, decreasing from 122 ± 38.8 mg/dL in the pre-intervention phase to 108 ± 32.1 mg/dL after surgery. The mean difference was 13.8 mg/dL (P = 0.003), corresponding to a relative reduction of 11.3%. Although the magnitude of change was smaller than that observed for HDL-C and triglycerides, the reduction in LDL-C was statistically significant and was graphically reflected by a shift toward lower values in the postoperative period (Figure 3), along with reduced dispersion of extreme values.

Triglycerides exhibited the greatest magnitude of change within the lipid profile, with a marked reduction from 167.6 ± 75.4 mg/dL in the pre-intervention period to 123.7 ± 51.1 mg/dL during postoperative follow-up. The mean difference was 46.6 mg/dL (P < 0.001), representing a clinically significant relative decrease. Figure 3 show a clear reduction in the median and IQR of triglyceride levels, as well as fewer elevated values in the postoperative period, suggesting a generalized favorable response across the cohort.

Overall, the changes observed in the lipid profile after bariatric surgery demonstrate a global improvement in atherogenic risk, characterized by increased HDL-C levels and significant reductions in triglycerides and LDL-C. These findings were consistently observed in the graphical representations of the overall cohort.

Behavior of hypertension stages before and after bariatric surgery

Figure 4A shows the percentage distribution of changes in hypertension grade after bariatric surgery, stratified by patients initially classified as stage I or stage II. Among patients with stage I, 50% improved their BP category, achieving normotension or requiring lower medication intensity. Forty-six percent remained unchanged, while only 4% experienced worsening.

Figure 4 Behavior of hypertension stages before and after bariatric surgery. A: Classification of hypertension stages at baseline and postoperatively; B: Pharmacological management of diabetes, hypertension, and dyslipidemia before and after surgical intervention.

In contrast, among patients with stage II, the majority (70%) remained unchanged, 20% showed improvement, and 10% experienced worsening of BP control.

Regarding pharmacological treatment within the overall cohort, a global reduction in medication use was observed after bariatric surgery, consistent with the improvements in metabolic and lipid parameters achieved following the procedure.

Among patients with T2D, 53% were able to maintain or reduce therapy to a single medication, whereas only 10% continued to require combination therapy. In patients with hypertension, 37% achieved BP control with monotherapy, and only 18% remained on dual therapy. Among patients diagnosed with dyslipidemia, 44% were able to control their lipid profile with monotherapy (mainly statins), without the need for combination pharmacological treatment (Figure 4B).

Changes in glycemic parameters according to diabetic status

In the non-diabetic group (n = 36), HbA1c showed a slight increase after bariatric surgery, rising from 4.5% ± 0.4% preoperatively to 5.4% ± 0.4% postoperatively (P = 0.002). In contrast, FPG decreased from 98.8 ± 10 mg/dL to 87.1 ± 8.9 mg/dL, although this reduction did not reach statistical significance (P = 0.08).

In the diabetic group (n = 25), HbA1c decreased significantly following surgery, from 7.1% ± 1.8% at baseline to 5.8% ± 0.7% postoperatively (P = 0.020). Fasting glucose also declined, from 114.1 ± 16.6 mg/dL to 88.3 ± 14.1 mg/dL, although this change did not reach statistical significance (P = 0.08) (Supplementary Figures 1 and 2).

When comparing both groups, patients with diabetes had substantially higher baseline HbA1c and fasting glucose levels than non-diabetic patients. Following bariatric surgery, the absolute reduction in HbA1c was markedly greater in the diabetic group, indicating a more pronounced improvement in glycemic control. Similarly, the decrease in fasting glucose was more pronounced among diabetic patients, whereas the reduction observed in non-diabetic individuals was smaller, likely reflecting their near-normal baseline glycemic values.

Changes in lipid profile according to glycemic status

Subgroup analyses showed improvements in the lipid profile following bariatric surgery across all baseline glycemic categories.

Among non-diabetic patients (n = 37), HDL cholesterol increased from 46.3 ± 13.5 mg/dL to 55.3 ± 22.3 mg/dL, while LDL cholesterol decreased from 126.5 ± 35.5 mg/dL to 109.0 ± 33.7 mg/dL. Triglyceride levels also declined from 169.3 ± 75.7 mg/dL to 122.3 ± 55.9 mg/dL.

In patients with diabetes (n = 25), HDL cholesterol increased from 40.6 ± 11.9 mg/dL to 50.2 ± 13.0 mg/dL, whereas LDL cholesterol showed a more modest reduction from 113.9 ± 36.0 mg/dL to 106.0 ± 28.8 mg/dL. Triglycerides decreased from 164.0 ± 76.4 mg/dL to 126.6 ± 40.6 mg/dL.

Among patients with prediabetes (n = 20), HDL cholesterol increased from 46.5 ± 11.2 mg/dL to 51.3 ± 15.6 mg/dL, LDL cholesterol decreased from 129.4 ± 29.6 mg/dL to 110.4 ± 30.0 mg/dL, and triglycerides declined from 165.3 ± 68.3 mg/dL to 138.0 ± 75.0 mg/dL (Supplementary Figures 3 and 4).

DISCUSSION

In this descriptive observational study, anthropometric and metabolic changes were evaluated in a cohort of patients who underwent bariatric surgery at a high-complexity hospital in Colombia. The results show a high baseline metabolic burden and show that, during early follow-up, clinically relevant reductions in body weight and BMI were observed, along with consistent improvements in lipid profile, glycemic control, and arterial hypertension stages.

In the present study, weight loss was primarily analyzed using the percentage of %TWL. According to the ASMBS reporting standards, %TWL is increasingly recognized as a more reliable and less confounded metric than percentage of excess weight loss (%EWL), as it is less dependent on the patient's baseline BMI. Our observed mean %TWL of 24.2% at 12 months is consistent with high-volume international cohorts, where sleeve gastrectomy typically yields a %TWL ranging from 20% to 30% during the first postoperative year[18,21]. Concordantly, the decrease in BMI from ranges of severe obesity to categories of overweight or class I obesity in most patients reflects a clinically meaningful weight response, even when considering the individual heterogeneity observed in the distribution of anthropometric values.

The substantial weight loss observed in our cohort is consistent with findings from recent systematic reviews and meta-analyses evaluating long-term outcomes after sleeve gastrectomy. Contemporary evidence indicates that sleeve gastrectomy results in durable weight reduction, with excess weight loss frequently exceeding 50% and being maintained for more than five years after surgery. In addition, metabolic improvements-including better glycemic control and cardiovascular risk reduction-have been consistently reported across large pooled analyses and long-term observational studies[29,30]. These findings support sleeve gastrectomy as an effective and durable metabolic intervention for patients with obesity and associated metabolic disease.

The effect size (Cohen’s d) for weight reduction was 2.01, suggesting a massive clinical impact of the sleeve gastrectomy in this Colombian population.

Regarding the lipid profile, the findings of this study are consistent with previous evidence. The significant increase in HDL cholesterol, close to 20% compared with baseline values, represents one of the most relevant changes from a cardiovascular standpoint, given its protective effect against atherosclerotic disease. Large observational studies, including the Swedish Obese Subjects Study, have documented similar increases in HDL cholesterol after bariatric surgery, attributed both to weight loss and to surgery-induced metabolic changes[18,22]. The graphical representation of the cohort showed a clear upward shift in the median and IQR toward higher values, suggesting a generalized favorable response.

Conversely, the reduction observed in triglyceride levels was the greatest in magnitude within the lipid profile, with a decrease of approximately 28% compared with baseline values. This finding is consistent with reports from the international literature, which describe reductions of 30%-50% during the first year after surgery, associated with improvements in insulin sensitivity, decreased hepatic production of triglyceride-rich lipoproteins, and reduced hepatic lipogenesis[15,22]. The reduction in LDL cholesterol, although of smaller relative magnitude, was statistically significant and consistent with previous reports, in which changes in LDL cholesterol after bariatric surgery have been described as more modest and variable, depending on the type of procedure and the concomitant use of lipid-lowering therapy[17,21].

The observed improvements in lipid profiles within our cohort are consistent with recent evidence. According to the 2023 ESC Guidelines for the management of cardiovascular disease in patients with diabetes, metabolic surgery is identified as a potent intervention to mitigate atherosclerotic cardiovascular disease risk. Recent reviews highlight that the sustained reduction in LDL-C and triglyceride levels following sleeve gastrectomy contributes to a favorable long-term cardiovascular risk trajectory, comparable to intensive lipid-lowering pharmacological therapy. Our results reinforce the notion that metabolic surgery acts as a primary prevention strategy, effectively modifying the metabolic environment that drives atherogenesis in patients with obesity and T2DM[6].

Regarding glucose metabolism, the reductions in FPG and HbA1c observed in this cohort are concordant with studies that have documented decreases in HbA1c ranging from 0.5% to 1.5% points during the first year after surgery[20,21]. Clinical trials such as the STAMPEDE study have demonstrated that these changes may occur early, even before substantial weight loss, suggesting additional physiological mechanisms related to increased incretin secretion and improved insulin sensitivity[20].

The metabolic benefits observed after bariatric surgery are not solely explained by weight reduction. In addition to the substantial decrease in body weight documented in our cohort, metabolic surgery induces a complex series of physiological changes that contribute to improvements in glucose and lipid metabolism. Enhanced secretion of incretin hormones, particularly glucagon-like peptide-1 (GLP-1), plays a central role in postoperative metabolic regulation by improving insulin secretion, glucose homeostasis, and satiety[31]. Furthermore, alterations in bile acid metabolism following procedures such as sleeve gastrectomy may activate signaling pathways mediated by nuclear receptors including the farnesoid X receptor and the membrane receptor TGR5, which influence glucose regulation and lipid metabolism[32]. Bariatric surgery has also been associated with significant shifts in gut microbiota composition, potentially modulating energy balance, inflammatory pathways, and host metabolic regulation[33,34]. Importantly, several studies indicate that some metabolic improvements occur early after surgery, even before substantial weight loss is achieved, supporting the concept of weight-independent metabolic effects of metabolic surgery[35,36]. These mechanisms collectively help explain the improvements in glycemic control and cardiometabolic risk observed in our cohort and are consistent with current international guidelines that recognize metabolic surgery as an effective therapeutic strategy for obesity and T2D when conventional medical therapy is insufficient[37].

The STAMPEDE trial also demonstrated superior glycemic control compared to intensive medical therapy. Crucially, long-term follow-up data (5-10 years) from the STAMPEDE trial have confirmed the durability of diabetes remission, showing that a significant proportion of patients maintain HbA1c levels below the diagnostic threshold for diabetes for up to a decade post-procedure[20]. Our findings in this Colombian cohort, while reporting on a shorter timeframe, align with this pattern, suggesting that the initial physiological shifts observed post-sleeve gastrectomy provide a foundation for long-term metabolic stability.

A limitation of this study is the inability to formally classify diabetes remission according to the ADA/ASMBS consensus criteria. Due to the retrospective design, a considerable proportion of patients lacked complete follow-up data required for these definitions, particularly fasting glucose measurements and detailed documentation of antidiabetic medication discontinuation. Therefore, glycemic outcomes were primarily assessed through changes in HbA1c levels and patterns of antidiabetic medication use. Future prospective studies with standardized metabolic follow-up would allow a more precise evaluation of diabetes remission after bariatric surgery in this population.

With respect to arterial hypertension, a favorable redistribution of BP stages was observed, with a marked reduction in the proportion of patients classified as stage II and II after the intervention. We differentiated between clinical improvement and remission based on the 2023 ESC Guidelines for the management of cardiovascular disease in patients with diabetes. Improvement was defined as a reduction in antihypertensive medication dosage or a decrease in BP stages, whereas remission was defined as achieving a BP target of < 130/80 mmHg without the use of pharmacological therapy. In our cohort, while a significant proportion of patients achieved BP levels below the 130/80 mmHg threshold, true clinical remission-defined as normotension off-medication-was less frequent than glycemic remission. This discrepancy underscores that while metabolic surgery effectively reduces cardiovascular risk, the vascular and structural remodeling associated with long-standing hypertension may require sustained pharmacological support even after significant weight loss.

This pattern has been described in multiple studies, reporting improvement or normalization of BP in approximately 50%-65% of patients undergoing bariatric surgery[14,18]. Although this study did not assess major cardiovascular outcomes or perform a longitudinal analysis of BP, the reduction in hypertension severity and in the need for pharmacological treatment constitutes a clinically relevant finding during early follow-up.

Although formal remission of diabetes, hypertension, or dyslipidemia was not systematically evaluated in this study, the observed reductions in glycemic and lipid parameters together with the reduction in pharmacologic therapy suggest clinically meaningful metabolic improvement.

From a clinical and epidemiological perspective, these results are particularly relevant in the Colombian context, where the prevalence of obesity and excess body weight continues to rise and local evidence on bariatric surgery remains limited[7,8]. The detailed characterization of metabolic and therapeutic variables in a real-world clinical practice setting provides valuable information for postoperative follow-up and for the planning of comprehensive management strategies in patients with severe obesity.

Nevertheless, this study has limitations that should be considered when interpreting the findings. Its descriptive, observational, and retrospective design precludes the establishment of causal relationships or the estimation of the effect of surgery compared with other interventions. The relatively small sample size, the single-center setting, and the absence of a control group limit the generalizability of the results. In addition, long-term outcomes were not evaluated, nor was adjustment performed for concomitant pharmacological treatment, factors that could influence some of the observed metabolic changes. Despite these limitations, the study has important strengths, including the consecutive inclusion of patients, the use of real-world clinical data, and the systematic assessment of multiple relevant metabolic variables. Taken together, these findings are consistent with previous evidence describing metabolic improvements after bariatric surgery and highlight the need for prospective, multicenter studies with long-term follow-up to evaluate the sustainability of these changes and their impact on major cardiovascular outcomes in the Colombian population.

It is important to acknowledge the heterogeneity of metabolic responses observed in this cohort. Although overall trends indicated improvements in several cardiometabolic parameters, including glycemic control, lipid profile, and BP, the magnitude of change varied across individuals. For example, LDL cholesterol showed modest changes with considerable variability, and graphical analyses indicated that some patients experienced limited improvement or even worsening in certain parameters during follow-up. These findings highlight the complexity and interindividual variability of metabolic responses following bariatric surgery.

Despite the significant metabolic improvements observed, other limitations must be acknowledged. Our analysis did not adjust for the preoperative use of GLP-1 receptor agonists or sodium-glucose cotransporter 2 inhibitor inhibitors, which may influence early postoperative glycemic trajectories and weight loss independent of the surgical procedure. The nutritional status and potential micronutrient deficiencies (e.g., vitamin B12, iron, or vitamin D) were not systematically evaluated, which is a critical aspect of long-term follow-up in bariatric patients. Finally, the 12-month follow-up period limits our ability to assess long-term cardiovascular outcomes, such as the incidence of major adverse cardiovascular events or the long-term durability of the observed metabolic benefits beyond the first postoperative year.

An additional strength of this study lies in its real-world clinical perspective. Unlike randomized controlled trials, which often include highly selected patient populations under strictly controlled conditions, the present cohort reflects the diversity and complexity of patients undergoing bariatric surgery in routine clinical practice at a high-complexity hospital in Colombia.

This study provides one of the first detailed characterizations of the baseline metabolic burden and early postoperative metabolic changes in a cohort of patients undergoing bariatric surgery in a high-complexity hospital in Colombia. The findings contribute valuable real-world evidence regarding metabolic outcomes and reductions in pharmacological treatment burden in routine clinical practice. Although the retrospective design and sample size limit the ability to draw causal inferences, the results highlight the need for prospective, multicenter studies with longer follow-up in similar populations.

CONCLUSION

Bariatric surgery, performed through sleeve gastrectomy in this cohort, was associated with significant reductions in body weight and improvements in metabolic parameters during early follow-up. Patients exhibited substantial decreases in glucose levels and HbA1c, as well as a more favorable lipid profile and a reduced need for pharmacological treatment. These findings are consistent with previous evidence suggesting that bariatric surgery is associated with significant weight loss and metabolic improvements, reaffirming the value of bariatric surgery not only as an effective strategy for weight control but also as a therapeutic tool capable of substantially improving metabolic health. However, the relationship between the magnitude of weight loss and the metabolic response was not linear, suggesting the involvement of additional hormonal and physiological mechanisms. Although the study has limitations inherent to its design and sample size, the findings contribute to strengthening local evidence regarding the benefits of bariatric surgery and underscore the importance of maintaining structured long-term follow-up to assess the sustainability of these results over time.