Efficacy of Intermittent Fasting Versus Continuous Caloric Restriction in the Treatment of Significant Weight Regain After Bariatric Surgery

NCT06766747 | Completed DMC

• 1 other identifier: FM-CIE-0622-23
• Study Type: interventional
• Target: 16
• Locations: 1 country
• Sites: 1

Brief Summary

Intermittent fasting has gained relevance in recent years because it allows for significant weight loss with improvement in cardiovascular risk factors similar to calorie-restricted diets without people having to track calories every day, or prohibiting people from eating certain food groups. However, there is no data about its usefulness in patients with weight gain after bariatric surgery, or its long-term effects(9). Research question: In patients with weight gain, being followed up in the obesity clinic, is intermittent fasting for 12 weeks, compared to calorie restriction, effective in terms of weight reduction? H0: Change in weight from baseline to 12 weeks less than 5% H1: Change in weight from baseline to 12 weeks greater than or equal to 5% Patients meeting the inclusion criteria will be identified. Once identified, they will be asked to participate in the study and, if they accept, they will be asked to complete and sign the informed consent form. The study will consist of three phases: a selection phase, an adaptation phase (1 to 2 weeks), a weight loss phase (12 weeks) and a maintenance phase (12 weeks). At the first visit, patients will be randomized to two types of nutritional interventions: intermittent fasting or caloric restriction. During the weight loss phase, biweekly follow-up will be performed to ensure adherence to the assigned dietary intervention. At the end of the 12 weeks, patients can decide whether to continue the assigned dietary intervention or move to a maintenance plan. Anthropometric measurements and body composition will be measured at baseline, 12 and 24 weeks.

Conditions

Obesity Prevention; Bariatric Surgery Complications; Intermittent Fasting

Keywords

Gain Weight Following Bariatric Surgery; Intermittent Fasting

Outcome Measures

Primary Outcomes (1)

• Weight loss (Kg)

  To evaluate the efficacy of intermittent fasting (5:2 diet) for 12 weeks, compared with continuous caloric restriction, in terms of weight reduction in kilograms (Kg), in patients with weight regain.

  12 weeks

Secondary Outcomes (9)

• Percentage of fat mass

  12 weeks

• Visceral fat

  12 weeks

• Percentage of lean mass

  12 weeks

• HbA1c

  12 weeks

• Weight 24 weeks

  24 weeks

Study Arms (2)

Intervention group

ACTIVE COMPARATOR

Participants in the alternate-day fasting group will receive biweekly telecounseling to ensure adherence to the prescribed dietary plan and to monitor for potential adverse events. During the 12-week weight loss phase, patients are instructed to restrict calories to 75% of usual intake 2 days per week. A daily intake of at least 2 liters of low-energy beverages (water, caffeine- and sugar-free beverages) is generally recommended on fasting days. Usual physical activity is encouraged to continue except on fasting days.

Other: Intermittent Fasting

Control group

PLACEBO COMPARATOR

Participants in the continuous calorie restriction group will receive biweekly nutritional counseling via telecoaching to ensure adherence to the prescribed dietary plan. Based on the weekly caloric intake obtained from the 7-day log, a model menu will be prescribed with 25% daily caloric restriction divided into 3 meals per day consisting of macronutrient intake with 20% of energy as fat, 40 to 50% as carbohydrate, and 20 to 30% as protein. They are instructed to continue their usual physical activity.

Other: Continuous calorie restriction

Interventions

Intermittent Fasting OTHER

Participants in the alternate-day fasting group will receive biweekly telecounseling to ensure adherence to the prescribed dietary plan and to monitor for potential adverse events. During the 12-week weight loss phase, patients are instructed to restrict calories to 75% of usual intake 2 days per week. A daily intake of at least 2 liters of low-energy beverages (water, caffeine- and sugar-free beverages) is generally recommended on fasting days. Usual physical activity is encourage

Intervention group

Continuous calorie restriction OTHER

Participants in the continuous calorie restriction group will receive biweekly nutritional counseling via Telecoaching to ensure adherence to the prescribed dietary plan. Based on weekly caloric intake obtained from the 7-day log, a model menu will be prescribed with a 25% daily calorie restriction divided among 3 meals every day consisting of macronutrient intake, with 20% of energy as fat, 40 to 50% as carbohydrate, and 20 to 30% as protein. They will be instructed to continue their usual physical activity.

Control group

Eligibility Criteria

• Age: 18 Years - 69 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• % weight gain with respect to the minimum postoperative weight and/or
• Weight gain rate ≥0.50% with respect to previous weight.
• Supplementation with ferrous sulfate, cyanocobalamin and cholecalciferol, according to clinical criteria.
• Not having modified the therapy in the last 3 months
• Access to mobile phone with data.
• Agree to participate in the study including signing informed consent.

You may not qualify if:

• Patient diagnosed with type 1 diabetes mellitus.
• Patient diagnosed with type 2 diabetes mellitus treated with insulin.
• History of an eating disorder such as anorexia or bulimia. • Untreated vitamin B12, iron, calcium, and/or vitamin D deficiency.
• History of hospitalization for cardiovascular disease (angina, myocardial infarction, or stroke) 3 months prior to the study.
• Use of antidepressant or anti-anxiety medications
• Use of medications that affect the results of the study (weight loss medications)
• Unable to keep a food diary or activity log for 7 consecutive days during screening
• Cognitive impairment that, in the opinion of the principal investigator or study physician, would result in failure to cooperate with study procedures.
• Active neoplastic disease.
• Pregnancy or breast-feeding, or planning to become pregnant during the study period
• Significant psychiatric illness, kidney disease, severe liver disease, or other illness that affects the ability to complete the study.

Sponsors & Collaborators

• Hospital Universitario San Ignacio: lead
• Pontificia Universidad Javeriana: collaborator

Study Sites (1)

Hospital Universitario San Ignacio.

Bogotá, Bogota D.C., 111021, Colombia

Location

MeSH Terms

Conditions

Intermittent Fasting

Condition Hierarchy (Ancestors)

Fasting; Feeding Behavior; Behavior

Study Officials

• Diana C Henao, Endocrinologyst

  Hospital Universitario San Ignacio

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Masking Details: person in charge of statistical analysis and investigators.
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: December 27, 2024
• First Posted: January 9, 2025
• Study Start: December 19, 2023
• Primary Completion: January 31, 2025
• Study Completion: June 30, 2025
• Last Updated: September 25, 2025

Record last verified: 2025-09

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR, ANALYTIC CODE

Locations

CO (1)