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 Table of Contents  
Year : 2023  |  Volume : 2  |  Issue : 2  |  Page : 85-92

Investigating the impact of very low-calorie diet in patients' postbariatric surgery with weight regain: A randomized, prospective, interventional, and pilot study

1 Department of Clinical Nutrition and Dietetics, Max Super Specialty Hospital, New Delhi, India
2 Lady Irwin College, University of Delhi, New Delhi, India

Date of Submission17-Apr-2023
Date of Acceptance26-May-2023
Date of Web Publication04-Aug-2023

Correspondence Address:
Ritika Samaddar
Department of Clinical Nutrition and Dietetics, Max Super Specialty Hospital, Saket, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jbs.jbs_8_23

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Objective: The objective of the study is to evaluate the effect of very low-calorie diet (VLCD) on postbariatric surgery (BS) patients with weight regain (WR). Methods: This is a prospective, randomized, controlled, interventional clinical trial. The sample selection for the study was performed on the basis of prepared inclusion and exclusion criteria. Structured phone calls were made to all the subjects in which baseline information such as body weight and height were asked through which body mass index (BMI) was calculated to check the eligibility. A sample size of 40 subjects including both males and females with >10% gain of nadir weight after 2 years of BS with a current BMI of ≥30 kg/m[2] was selected. Two standardized VLCD plans for 4 weeks each were prescribed to them. A close supervision of selected subjects was done regularly through structured weekly calls, outpatient department follow-ups, and support group meets. The statistical analysis was done to find the average weight loss (WL) and change in body fat percentage over 8 weeks. Results: The mean average age of the sample was 45 ± 9.45 years among which 12 were male and 28 were female. The sample size was under the inclusion criteria with >10% WR after 2 years of BS. In this sample, the average total body WL after BS was found to be 47.3 kg. Postoperative average WR in the selected sample was 10.3%. After the follow-up period of 8 weeks of VLCD, an average WL of 3.66 kg (3.76%) along with a body fat percent loss of 2.58% was observed. It was also noted that the WL in the initial weeks was comparatively higher than that in the later weeks. An average WL in the first 4 weeks was 2.36 kg (2.42%) and average WL in the next 4 weeks was 1.32 kg (1.35%). Conclusion: VLCD is effective but long-term effects need to be seen. There have been no such Indian studies before this, and hence, more such studies need to be done.

Keywords: Average, bariatric surgery, body mass index, ideal body weight, total body weight, total body weight loss, type 2 diabetes mellitus, very low-calorie diet, weight loss, weight regain

How to cite this article:
Samaddar R, Pawha S, Sharma K. Investigating the impact of very low-calorie diet in patients' postbariatric surgery with weight regain: A randomized, prospective, interventional, and pilot study. J Bariatr Surg 2023;2:85-92

How to cite this URL:
Samaddar R, Pawha S, Sharma K. Investigating the impact of very low-calorie diet in patients' postbariatric surgery with weight regain: A randomized, prospective, interventional, and pilot study. J Bariatr Surg [serial online] 2023 [cited 2023 Sep 29];2:85-92. Available from: http://www.jbsonline.org/text.asp?2023/2/2/85/382975

  Introduction Top

Obesity is a global issue, its prevalence is increasing day by day affecting more than 2.1 billion people worldwide.[1] It is increasing the burden of diseases, as it is a major risk factor for several diseases.[2] Bariatric surgery (BS) is an effective method for managing excess body weight, which results in a 60%–75% reduction in excess body weight. Maximum weight loss (WL) occurs during 18–24 months postoperatively.[3] In a high percentage of cases, comorbidities associated with obesity are remitted, and mortality is reduced using BS procedures.[4]

Due to the reduced gastric capacity, decreased hunger, and increased satiety caused by anatomical and metabolic changes, BS reduces caloric intake in the immediate postoperative period leading to WL. Ghrelin hormone helps in regulating the appetite and energy balance. After BS, a significant reduction in both fasting and postprandial ghrelin is observed resulting in decreased appetite and food intake, which is one of the reasons of rapid WL after BS.[5] BS can achieve WL, treat obesity-related metabolic disease, and improve metabolic status by improving hypertension, type 2 diabetes mellitus, and lipid profile, thereby lowering cardiovascular risk.[6]

Despite the fact that most BSs result in effective WL, weight regain (WR) may happen over a long period of time [Figure 1], with 20%–30% of patients either failing to attain their objective weight goals or failing to sustain the WL achieved.[7] After BS, 20%–25% of lost weight can be regained over 10 years.[8]
Figure 1: Causes, predictors, and prevention of weight regain[7]

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According to a meta-analysis, physical activity after BS was substantially related with higher WL.[9] According to the studies, only 10%–24% of post-BS patients met the physical activity guidelines of 150 min/week of moderate-to-vigorous physical activity.[10] People with severe obesity are at more risk of sedentary behavior.

Conventional weight reducing diets with 500–600 kcal/day result in a WL with a rate of around 0.5 kg/week. Reduced weight, energy restriction, and reduced abdominal fat result in reduced liver glucose synthesis, which help in the reversion of diabetes.[11] In significantly nonsurgical individuals with obesity, very low-calorie diets (VLCDs) of 400–800 kcal/d induce short-term WL of 20%–25% of their initial weight.[12]

Portion control and low-calorie diets in post-BS patients are helpful in the management of pouch distension that may happen in the long-term operative patients. In a study of 4–6 weeks, more than 70% of patients experienced success with the conservative management of pouch distension, which includes complete band deflation, a low-calorie diet, and reinforcement of portion control.[13]

The composition and type of food sources in VLCD play an important role. Protein intake after surgery is not only associated with improvement in satiety and WL but also improved nutritional status (increase in muscle mass and reduction in fat percentage).[14] Protein-rich foods (e.g., dairy products, eggs, fish, lean meat, soy products, and legumes), especially food rich in leucine, should be preferred over foods rich in carbohydrates or fats as leucine helps in maintaining lean tissue.[14] Patients should be recommended to eat low-fat and protein-rich foods such lean meat, skimmed milk, and low-fat cheese over high-fat containing food items such as organ meat and cream-based dairy products. Protein supplements are helpful in achieving this target.[15]

A multidisciplinary approach should be used to manage WR including nutritional intervention, behavioral counseling, lifestyle changes, medication, and if necessary, surgical revision.

  Objectives Top

Primary objective

  • To determine the effectiveness of a VLCD in post-BS patients with WR.

Secondary objectives

  • Change in body fat percentage
  • To check compliance with VLCD.

  Methods Top

The study aimed to show the effects of VLCD on post-BS patients with WR. This is a prospective, randomized, controlled, interventional clinical trial, with a sample size of 40 subjects including both males and females with >10% gain of nadir weight after 2 years of BS with a current body mass index (BMI) of ≥30 kg/m[2].

Eligible subjects were prescribed two standard VLCD plans for a period of 4 weeks each.

To ensure adequate consumption, diet plans containing 27.2%–28.3%, 31.9%–32.3%, and 30.8%–44.6% energy from protein, carbohydrates, and fats were given to the subjects in this trial.

The diet charts were designed to provide a good balance of macro and micronutrients while also meeting the recommended water and fiber consumption.

Sample selection

It was done through purposive sampling. Subjects eligible for inclusion criteria were selected and those who were not eligible for the inclusion criteria were excluded [Figure 2]. The sample selection was done from follow-up post-BS patients from Max Super Specialty Hospital.
Figure 2: Flow chart of the study design. VLCD: Very low-calorie diet, WR: Weight regain, BMI: Body mass index

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A structured phone interview was conducted in which the purpose of the study and follow-up pattern was explained to the selected sample. Patient's oral agreement to participate and consent was done, and then, information was collected based on planned data collection forms, which included the information such as patient's age, general health condition, height, current weight, and weight at the time of surgery.

Sixty-two patients were enrolled for the study, 12 did not attend the scheduled interview, 2 refused to participate in between the study, 1 lost a family member so had to discontinue, 4 moved to other states, 2 had other medical complications, and 1 was excluded as had COVID-19 during the study. The selected sample size, which followed the plans for 8 weeks, was 40. The data analysis and discussion were done based on this sample size of 40 patients.

Tools used for data collection

Telephonic interviews and face-to-face outpatient department (OPD) visits or meetings through support group meets were done.

A data collection form was prepared based on which scheduled telephonic interviews were done. Standardized weekly VLCD plans were prepared and given to the selected samples. Weekly telephonic calls and in between OPD visits were done for follow-ups.

Duration of study

The implementation period of the research study was 8 weeks, which was conducted from March 2022 to April 2022.

Statistical analysis

The data collected was coded on MS Excel. The data were analyzed with the help of the Statistical Package for the Social Sciences (version 28, 2020 IBM SPSS Statistics). Descriptive and inferential statistics were used to describe the data and conclusions of the study. The analysis was done in terms of finding the average WL percentage and its 95% confidence interval using the Gaussian distribution. Crosstabs with the Chi-square test was used to identify the associations between different parameters. Significance was assessed at P < 0.05.

The analysis was done based on various parameters [Figure 2]. [Table 1] and [Figure 3] shows the baseline characteristics of the study participants.
Figure 3: Number of males and females in the sample size

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Table 1: Summary of subject's baseline characteristics

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  Results Top

The study population comprised 40 post-BS patients with >10% gain of nadir weight with an average current BMI >30 kg/m[2].

The average total body WL (TBL) of the study population after BS was reported to be 47.3 kg.

WR postsurgery was an average of 10.3% in patients operated between 2013 and 2019.

The study population was given a standardized VLCD for 8 weeks. The average WL was 3.66 kg (3.76%) with percent fat loss of 2.58%.

It was noted that WL was higher in the first 4 weeks (2.36 kg, 2.42%) compared to the next 4 weeks [1.32 kg, 1.35%; [Figure 4]] due to low compliance. [Figure 5] shows the average weight comparison of the study sample.
Figure 4: Weight loss trend in subjects following VLCD plans for 8 weeks. VLCD: Very low-calorie diet

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Figure 5: Average weight comparison of the sample. BW: Body weight, VLCD: Very low-calorie diet

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The study showed that WL is dependent on compliance; if compliance decreases, WL also decreases [Figure 6].
Figure 6: The relation between compliance and WL. WL: Weight loss

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In this study, during the detailed interview sessions, subjects mentioned that increased hunger pangs, disturbed sleeping pattern, increased appetite, poor adherence to diet, and lack of physical activities are among the major causes for postoperative WR.

  Discussion Top

Bariatric surgeries result in effective WL. However, over a period, caloric intake gradually increases in some patients, contributing to postoperative WR. In the Swedish obesity study, gradual increases in daily intake of 900, 1500, 1700, 1800, 1900, and 2000 kcal/day were reported in the period of 6 months to 4–10-year postsurgery with an increase in food intake observed from the 2nd postoperative year.[6] Research conducted by Shantavasinkul et al., 2016 on 1426 patients found that 17.1% of the sample regained more than 15% of their 1-year postoperative weight after 2 years of BS.[16]

Food indiscretion such as excessive calorie intake, snacks, sweets, oils, and fatty foods was statistically higher in patients with WR.[17] Grazing is one of the reasons associated with poor WL in post-BS patients. A 16.6%–46.6% prevalence of grazing was found in a meta-analysis of 994 post-BS patients.[18] Studies found that there is a higher increase in BMI (5.3 kg/m[2] increase) of binge eaters as compared to BMI of nonbinge eaters (2.4 kg/m[2] increase) after 2–7 years of BS.[19]

A higher calorie intake that results in WR is also influenced by dietary nonadherence and consumption of high-calorie foods and beverages. A postoperative behavioral survey of 203 patients reported that dining out more frequently, consuming much food in the evening or at night, and eating many high-fat foods had a positive link with the severity of WR.[20]

Return to preoperative lifestyle pattern, poor postoperative consultations, and better food acceptability are associated causes of postoperative WR.[21] As per the Longitudinal Assessment of BS study on 2348 bariatric patients, low high-density lipoprotein cholesterol and hypertension were also linked to a worsening weight trajectory.[22]

Weight-reducing diets can help with WL. In a study, one-third of patients with severe obesity (≥40 kg/m[2]) were able to maintain a ≥15 kg WL for 1 year after following a VLCD regimen. However, in a follow-up of more than 1 year, it was found that one-fifth of the participants were able to maintain a 5–15 kg WL from the original weight.[23]

In a meta-analysis, average WL of 9.81 kg and approximately 8.3% body weight reduction were observed in the sample who followed VLCD for 4 weeks. On the other hand, average WL of 25.78 kg and approximately 17.2% body weight reduction were observed in subjects who followed a VLCD for 6 weeks.[24]

BS is an effective treatment for WL and comorbidities remission or improvement. It is the most effective and lasting treatment for patients with severe obesity. The average TBL of the study population after BS was reported to be 47.3kg. In a study conducted by Bastos et al., 2013, a 60%–75% reduction in excess body weight during postoperative period from 18 to 24 months were observed.[3] In the study by Benaiges et al., 2015, it was found that in a high percentage of cases, comorbidities associated with obesity are remitted, and mortality is reduced using BS procedures.[4]

This clinical trial throws light on the impact of VLCD on post-BS patients with WR. The study conducted by El Ansari and Elhag, 2021, also stated that WR may occur in the long-term postoperative patients, and the resulting causes of this also include hormonal causes and maladaptive lifestyle behavior, i.e., poor eating habits and physical inactivity. Surgical specific factors such as pouch distension are also responsible for this WR.[7] A study done by Eid et al., 2011, states that the portion control and low calorie diets in postoperative bariatric patients are helpful in the management of pouch distension.[13]

Adherence to diet along with adapting healthy lifestyle including physical activities in routine is helpful in the management of postoperative WR. This study focuses on one of the parameters, i.e., diet. It was found that the participants in the program lost an average weight of 3.66 kg (3.76%) in a span of 8 weeks by following two standardized VLCD plans[attached in the [Appendix 1], [Appendix 2], [Appendix 3], [Appendix 4].

[Table 2] shows the effect of VLCD on body weight and body fat percentage in selected subjects who underwent this trial.
Table 2: Summary of subject's characteristics after very low-calorie diets

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The trial clearly demonstrated that VLCD is effective in WL, but long-term compliance is an issue; it was discovered that with passage of time, VLCD compliance decreased. As seen in the trial, WL is dependent on compliance; if compliance decreases, WL also decreases. It was demonstrated that WL was higher in the first 4 weeks compared to the next 4 weeks. The findings could be explained by the monotony and lack of options or variety in the plans leading to lack of compliance. The success of the plan also depends on individual choices and determination for follow-ups. A study also highlighted that one of the reasons to people abandoning these diets is boredom from following an artificial type of diet or a desire to return to their normal diet habits. The study also concluded that the individual's perspective and motivation also cause the change; it was found that the WL strategies that work for the first time for initiating WL may not work for the second time or for maintaining WL and vice versa.[25]

Long-term VLCD compliance in the Indian population is a challenge because Indian diets are predominantly carbohydrate based, making adherence to a low-carbohydrate/high-fat diet for extended periods difficult.[25]

  Conclusion Top

VLCD is effective but long-term effects need to be seen. There have been no such Indian studies before this, and hence, more such studies need to be done to see the effectiveness of VLCD on WL in post-BS patients with WR.


  • The adherence of VLCD was self-reported
  • It was a short-term study of 8 weeks.


The publication of this manuscript for the Indian subcontinent was funded by OPTIFAST, a trademark owned by Nestlé Health Science. Nestlé Health Science was, however, not involved in the design and conduct of the study and the authors declare no conflict of interest.

Ethical approval

The protocol and informed consent form were approved by the Institutional Ethics Committee (IEC) (Max Healthcare Ethics Committee [MHEC]) on July 15, 2022. The study was undertaken in accordance with the International Conference on Harmonization Good Clinical Practice and the Declaration of Helsinki. All patients provided written informed consent.

The thesis study was approved by the IEC (MHEC) on July 15, 2022. The Institutional Scientific Committee (Max Super Specialty Hospital) has given approval to conduct the thesis study “Very Low Caloric Diet: Effects on Body Weight of Postoperated Bariatric Subjects – A Randomized Prospective Interventional Study” on June 14, 2022.

Author contributions

All authors contributed equally to this report. Ms. Ritika Samaddar, Ms. Saumya Pawha, and Ms. Khushboo Sharma have full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design

Ms. Ritika Samaddar, Ms. Saumya Pawha, and Ms. Khushboo Sharma.

Study supervision

Ms. Ritika Samaddar, Ms. Saumya Pawha, and Ms. Khushboo Sharma.

Acquisition, analysis, or interpretation of data

Ms. Ritika Samaddar, Ms. Saumya Pawha, and Ms. Khushboo Sharma.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Bastos EC, Barbosa EM, Soriano GM, dos Santos EA, Vasconcelos SM. Determinants of weight regain after bariatric surgery. Arq Bras Cir Dig 2013;26 Suppl 1:26-32.  Back to cited text no. 3
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