Effect of pre-operative weight loss on patients' outcomes undergoing laparoscopic sleeve gastrectomy.

Background: The study aims to demonstrate whether weight loss with a low-calorie diet before laparoscopic sleeve gastrectomy (LSG) may affect the outcomes. Materials and
Methods: A total of 305 patients undergoing primary LSG were included in the study. Each patient adopted a low-calorie diet (1000 calories) before LSG. The patients were stratified into two groups. Group A: Those who lost 3% or more of their total body weight loss (TBWL), Group B: Those who lost <3% of their TBWL. Two groups were compared in terms of operative time, length of hospital stay, complications and weight loss outcomes.
Results: One hundred and five patients (35%) were in Group A and 200 patients were in Group B. Median weight loss was 4 kg (3-20 kg). Pre-operative mean body mass index (BMI) was 40 ± 7.4 kg/m2 in Group A and 41 ± 5.9 kg/m2 in Group B (P = 0.06). At 1 year after the surgery, BMI regressed to 29.7 ± 4.9 kg/m2 in Group A and to 27 ± 4.2 kg/m2 in Group B (P < 0.001). One hundred and twenty-nine patients who completed 2 years of follow-up, mean BMI regressed to 29.4 ± 4.1 kg/m2 in Group A (n = 46) and to 27.2 ± 4.5 kg/m2 in Group B (n = 83) (P < 0.001). In Group B, one patient experienced post-operative bleeding. No other complications were observed in the study. There was no significant difference between the groups in terms of operative time (P = 0.53) and length of hospital stay (P = 0.9).
Conclusion: Weight loss before LSG does not improve post-operative weight loss.

INTRODUCTION

Obesity is a chronic disease, and currently, bariatric surgery is the most effective treatment to combat with it.[12] Laparoscopic sleeve gastrectomy (LSG) as a surgical method has become the most commonly performed technique, particularly in recent years.[34] A good pre-operative preparation before bariatric surgery may provide improved post-operative results.[56] For this purpose, most centres give their patients a low-calorie diet for 2–3 weeks before surgery. This practice primarily aims to reduce liver steatosis.[78] It is thought that this may allow better visibility and more convenience during the surgery as well as reducing intraoperative and post-operative complications. In addition, the pre-operative diet is expected to improve patient compliance and aid weight loss in the post-operative period. Whether the diet applied before bariatric surgery is effective in this regard remains controversial.[9] Our study aims to demonstrate whether weight loss with a 2-weeks low-calorie diet before LSG may affect surgery outcomes.

MATERIALS AND METHODS

This study was conducted at a private bariatric surgery centre and was approved by the Institutional Ethics Committee (ATADEK 2020-19/02). All patients were informed about the study in detail, and written consents were obtained. A total of 305 patients undergoing primary LSG between March 2018 and September 2020 who completed at least 1 year of follow-up were included in the study. Patients’ data, which were recorded prospectively, were analysed retrospectively. Patients with body mass index (BMI) over 50 kg/m2, who underwent revision surgery and those undergoing additional surgical procedures in the same session, were excluded from the study. Our pre-operative workup protocol and surgical technique has been previously described.[10]

Pre-operative workup

All the patients were screened by detailed laboratory tests with respect to metabolic parameters (liver, kidney, thyroid function, lipid profile, fasting blood glucose, insulin level, Hba1c, C peptide and uric acid) and vitamin deficiency (ferritin, B 12, folic acid, Vitamin D). Oesophagogastroduodenoscopy and abdominal ultrasound were performed for each patient. Each patient was evaluated by a multidisciplinary team (dietitian, psychiatrist, cardiologist, pulmonologist, endocrinologist and anaesthetist.

Pre-operative diet

Each patient adopted a low-calorie diet (1000 calories) for 2 weeks before the surgery. Patients were informed about the possible benefits expected from this diet.

Surgery

All LSG operations were done by the same team and the same technique. Using an optical trocar for the first entry, with a five-trocar technique, and sleeve gastrectomy over a 36 French bougie, starting 3–4 cm away from the pylorus was performed. The entire length of the staple line was reinforced using 3.0 V-Loc suture by continuous suturing (V-Loc 180; Medtronic, Minneapolis, MN).

All patients were followed up at the 3rd, 6th and 12th months after LSG and annually thereafter during which laboratory tests and clinical assessment were done. Patients’ baseline characteristics, co-morbidities, weight at the time of initial presentation, adherence to the low-calorie diet and weight measured with the same device on the morning of surgery were recorded. The patients who applied a low-calorie diet (1000 calories) for 2 weeks preoperatively were stratified into two groups. After evaluation of all patients, the percentage of mean total body weight loss (TBWL) was detected as 2.9% (0–11). Therefore, when grouping the patients according to the percentage of TBWL, 3% was taken as the cut-off value.

Group A: Those who lost 3% or more of their total body weight

Group B: Those who lost <3% of their total body weight.

Weight loss data are presented as per cent of excess weight loss (%EWL) and total weight loss (%TWL). For this calculation, the upper limit of BMI, i.e., 25 kg/m2 was taken as the reference value. The two groups were compared in terms of operative time, length of hospital stay, complications within the first 30 days after the surgery, BMI, %TWL and %EWL at 6 months, 1 year and 2 years postoperatively.

Statistical analysis was performed using SPSS software version 21 (IBM Corp. Armonk, NY, USA). Standard deviation and mean values were used for the variables with normal distribution and median values were used for the variables that were not normally distributed. Chi-square or Fisher's exact tests were used for categorical variables; while for continuous variables, independent-samples t-test or Mann–Whitney U-test were performed. P < 0.05 were considered statistically significant.

RESULTS

A total of 305 patients underwent primary LSG between March 2018 and September 2020. The mean age of the patients was 37.8 ± 12 years (53% of females) and the mean BMI was 41.7 ± 7 kg/m2. At baseline, 79%, 11%, 30%, 53% and 23% of the patients had insulin resistance, type-2 diabetes mellitus, hypertension, hyperlipidaemia and obstructive sleep apnoea, respectively. With the 2-week diet before the surgery, 105 patients (35%) lost 3% or more of their total body weight (Group A), while 200 patients (65%) lost <3% of their total body weight (Group B). Median weight loss was 4 kg (3–20 kg). There was no weight loss in 108 patients in Group B and 19 patients gained weight during the pre-operative period (min: 1 kg, max: 5 kg). The demographics of both groups are shown in Table 1.

Table 1

Patients characteristics

	Group A (TWL% >3%) (n=105), n (%)	Group B (TWL% <3%) (n=200), n (%)	P
Men/women	66/39	78/122	<0.001
Age (years)	37.2±12.8	38.1±11.4	0.56
Pre-operative BMI (kg/m2)	42±7.4	41±5.9	0.042
Co-morbidities (+)
Type 2 diabetes	12 (12)	21 (12)
İnsuline resistance	86 (88)	156 (88)
Hypertension	37 (35)	53 (26)
Dyslipidaemia	57 (55)	106 (53)
Sleep apnoea	31 (30)	40 (20)

Values are means±SDs, median (minimum-maximum) or number of subjects. Both groups were compared using independent samples t-test or Mann-Whitney U for continuous variables and Chi-squared test for categorical variables. BMI: Body mass index, TWL: Total weight loss

Pre-operative mean BMI was 40 ± 7.4 kg/m2 in Group A and 41 ± 5.9 kg/m2 in Group B. There were more men in Group A (63%) and more women (61%) in Group B (P < 0.001). At 1 year after the surgery, BMI regressed to 29.7 ± 4.9 kg/m2 in Group A and to 27 ± 4.2 kg/m2 in Group B (P < 0.001). Among the 129 patients who completed 2 years of follow-up, mean BMI regressed to 29.4 ± 4.1 kg/m2 in Group A (n = 46) and to 27.2 ± 4.5 kg/m2 in Group B (n = 83) (P < 0.001). %EWL at 1 year after the surgery was 80 ± 22.4% in Group A and 93 ± 28.1% in Group B (P < 0.001).

In Group B, a patient with BMI 37 kg/m2 experienced post-operative bleeding. No other complication was observed in the study. Median operative time was 94 min (min: 80 max: 140) for Group A and 95 min (min: 70 max: 120) for Group B (P = 0.53). Furthermore, there was no significant difference between the groups in terms of length of hospital stay (P = 0.9). Post-operative outcomes of both groups are shown in Table 2.

Table 2

Post-operative weight loss outcomes for both groups

Total: 305	Group A (pre-operative TWL% >3%) (n=105)	Group B (pre-operative TWL% <3%) (n=200)	P
Baseline BMI (kg/m2)	40±7.4	41±5.9	0.06
6th month mean BMI (kg/m2)	32.6±5.4	29.5±4.8	<0.001
6th month TWL (%)	26.1±5.5	28±8	0.03
6th month EWL (%)	61.7 (33-155)	74.2 (26-155)	<0.001
1st year mean BMI (kg/m2)	29.7±4.9	27±4.2	<0.001
1st year TWL (%)	32.7±7.1	33.4±7.7	0.4
1st year EWL (%)	80.2±22.4	92.7±28.2	<0.001
2nd year mean BMI (kg/m2)	29.4±4.1	27.2±4.5	<0.001
2nd year TWL (%)	32.3±10.2	34.7±9.5	0.18
2nd year EWL (%)	74.5±18.8	90.2±30	0.002

BMI: Body mass index, TWL: Total weight loss, EWL: Excess weight loss

DISCUSSION

Obesity has been rapidly increasing around the world, and accordingly, more patients are being operated for weight reduction every year.[4] Several centres in this field are focused on constantly improving their bariatric surgery programmes, including the pre-operative preparation period, to reduce complication rates and achieve better outcomes.[11] As part of these practices, patients in most centres apply a low-calorie diet for 2–3 weeks before surgery. Moreover, a relevant guideline supports weight loss before bariatric surgery.[12] This practice primarily aims to reduce liver steatosis.[78] It is thought that this may allow better visibility and more convenience during the surgery. Second, pre-operative diet is expected to improve patient compliance and aid in weight loss in the post-operative period. In this study, we concluded that losing weight before LSG had no effect and even had a negative effect on the success of post-operative weight loss (P < 0.001).

The comparison between patients who completed their 2-year follow-up after LSG also yielded the same result. Some studies on this subject matter have reported a positive relationship between pre-operative weight loss and post-operative weight loss[1314] whereas, some other publications have reported no such association.[1516] Interestingly, a negative correlation was observed in a study involving patients with gastric bypass, similar to the findings of our study. In that study, it was observed that patients who succeeded in losing weight preoperatively lost less weight after the surgery.[17]

A number of studies have reported that weight loss before bariatric surgery affects perioperative results, thereby shortening the operative time.[181920] Another study concluded that this practice improves visibility during the operation; although without any effect on operative time.[21] In this study, there was no difference between the two groups in terms of operative time (P = 0.53). Although the shorter length of hospital stay was observed in patients with pre-operative weight loss in a study,[22] many others reported no difference in length of hospital stay.[181920] Similarly, there was no difference between the two groups with regard to the length of hospital stay in the present study (P = 0.9).

The association between pre-operative weight loss and complications suggested in earlier publications remains unclear. Some studies have reported a higher rate of complications in patients who fail to lose weight preoperatively.[1723] A study in this field reported less blood requirement in patients who lost weight during the pre-operative period (1.4%–4.7%). Interestingly, the same study demonstrated a higher total rate of complications in those with pre-operative weight loss.[17] In the present study, a patient in Group B, whose BMI was 37 kg/m2, experienced post-operative bleeding. This patient underwent reoperation and the bleeding focus was found to be short gastric vessels. Bleeding was stopped and the patient recovered without complications. There was no other complication in either group in our study.

Our study had some limitations such as being a retrospective study. Furthermore, gender distribution rates between the groups were not equal. While the rate of male participants was higher in Group A, the rate of female participants was higher in Group B. The primary purpose of the pre-operative diet is to reduce liver size and intraabdominal fat. Since abdominal obesity in men is at higher rates, it may have enabled them to apply the pre-operative diet more carefully. Similarly, the lower rate of abdominal obesity in women may be one of the reasons why the pre-operative diet was not followed properly; therefore the weight loss was less in Group B. In addition, the better weight loss rate of Group B in the follow-up period, unlike the pre-operative period, maybe due to the better adapting of women to the rules to be followed after surgery.

CONCLUSION

This study has shown that weight loss before LSG does not improve post-operative weight loss during a 2-year follow-up. Furthermore, weight loss before LSG was not associated with shorter operative time or length of hospital stay. More randomised prospective trials are needed to confirm these findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.