Study design
We will carry out an 8-week double blind randomized controlled trial. The flow chart of the study is presented in Fig 1. This intervention will be conducted in the nutrition clinic of Shahid Beheshti University of Medical Sciences in Tehran, Iran, to evaluate the effect of TRF on anthropometric indices, eating behavior, stress, serum BDNF and LBP levels in women with overweight/obesity and food addiction.
The protocol is written in line with the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) checklist (Additional file 1).
Sample size
The number of participants was calculated according to the alterations in body weight, as a main variable. Determining the sample size for this study is based on how many samples should be selected so that the difference between the mean weight loss of TRF group from the control group is at least 2.3 kg (29), so that this difference with a probability of 95% (α=0.05) and power of 80% (β=20%) is statistically significant. Using this method, the number of samples in each group was estimated to be 26, which taking into account the 20% losses in the samples, 30 people will be included in each group. Collectively, a sample of 60 food addicted women with overweight or obesity will be enrolled.
Study population
Women with overweight or obesity (BMI: 26 - 39.9 kg/m2) and with food addiction will be recruited from nutrition clinic of Shahid Beheshti University of Medical Sciences (SBMU) through advertisement and face-to-face communication. The diagnosis of food addiction will be based on the YALE Food Addiction Scale (30). Women with overweight or obesity that obtain the necessary score will be enrolled in the study. Subjects who meet the inclusion criteria will be completely informed about the protocol of the study. Each participant will sign the informed consent form.
Inclusion and exclusion criteria
For the present study, 60 adult women with the following inclusion criteria will be included: aged 20-65 years; BMI: 26 - 39.9 kg/m2; willingness to participate in the study; confirmation of food addiction after obtaining the necessary score (at least 1 clinical score+ at least having 3 out of 7 criteria) from the YALE food addiction questionnaire; not having any diseases such as cancer, diabetes, newly hypothyroidism, renal or liver failure; non- pregnant or lactating; not perimenopause (women with irregular menstruation due to menopause or less than 2 years after amenorrhea); not participating in a weight loss diet during the last 2 months; were not smoker;
Patients will be excluded if: taking any antibiotics in the last 1 month or during the study; taking any medication affecting study outcomes regularly; using probiotic products (probiotic supplements, yogurt, cheese, cakes, biscuits and probiotic pasta) continuously (more than once a week) in the last month or during the study; using weight-loss or appetite-suppressing medications; drinking alcohol at any levels before or during the study; women with irregular menstruations. Also, we will exclude participants who refuse to continue the study, need antibiotics or have difficulties in fasting for 14 hours a day in the intervention group.
Randomization, sequence generation, and concealment
Participants will be randomly allocated into two groups: the group receiving a low-calorie diet with the time restricted feeding protocol or the control group receiving a low-calorie diet and will be followed up for 8 weeks. Stratified Blocked Randomization method is used to randomly assign people to two groups. The sequencing will be generated by one of the authors (AS) who is not going to assign participants into the study, so, allocation concealment will be ensured, as the author will not release the randomization code until the patient has been recruited into the trial by other authors (HI and BKh), which takes place after all baseline measurements have been completed. Participants are classified into overweight (26-29.9 kg/m2), grade 1 (30-34.9 kg/m2) and grade 2 obesity (35-39.9 kg/m2) based on BMI and randomly assigned to one of the control or TRF groups. Separate randomization is performed within each group for each BMI class. The size of the blocks is 4, two allocations are given to TRF group (A) and two allocations to Control Group (B). Six different permutations of AABB, ABAB, BBAA, BABA, ABBA and BAAB will be created.
Implementation
Potential participants will be invited to the study by HI and BKh. The sequencing will be generated by AS, who is not going to assign participants into the study.
Intervention
In this study, patients receive the relevant diets for 8 weeks based on the group they are placed in. In both groups, after calculating the amount of calories required by each individual using the Mifflin formula (31) as much as 300-500 kcal will be deducted from the total energy required for each person (a 500 kcal reduction from calorie is using for most of the cases, except for whom the calorie falls below 1200 kcal/d with 500 kcal reduction. In these cases, 300-400 kcal reduction will be used.) and accordingly, the low-calorie diet plan is given to each individual. The diet in each group will be consist of 50-55% carbohydrates, 15-20% protein and 30% fat. Patients in the TRF group will receive their meals from 10 hours a day from 10 am to 8 pm (32) while the control group will have less than 12 hours fasting.
Adherence
In order to control the participants in terms of adherence to the regimen and prevent the loss of samples, they will be followed up twice a week by phone call. At every phone call we will make sure if the cases are still in the study and they don’t have exclusion criteria (any need for antibiotic consumption, consuming probiotics, and …). Also, a 24h recall of the last day is obtaining from individuals and it is compared to their diet to make sure if they are adhering to the diet. The data of the patients with more than 90% compliance with the intervention will be analyzed.
Study outcomes
Primary outcomes of this clinical trial are the changes in anthropometric indices (including weight, BMI, hip circumference, waist-to-hip ratio, fat mass, muscle mass) and food addiction score. Secondary outcomes are changes in stress level, eating behavior, serum levels of BDNF and LBP.
After obtaining the informed consent, the general profile sheet will be completed for each patient. Also, at the beginning of the study, the weight of each patient with light clothing and with the accuracy of 100 grams and the height of each patient in a shoeless state will be measured by the meter mounted on the wall with an accuracy of 0.5 cm. Then, BMI of patients will be calculated and waist and hip circumferences are measured using meters with 0.5 cm accuracy. Also, waist-to-hip ratio will be calculated. Then, body fat mass and muscle mass are measured by bioelectrical impedance analysis. The participants' daily physical activity level will be measured using the Standard Physical Activity Questionnaire (MET). The validity of this questionnaire has been confirmed (33). Stress levels of subjects at the beginning and end of the study will be assessed using the Perceived Stress Questionnaire (PSS-14) (34). The scoring method is that based on the 5-degree spectrum, a score of 0-4 is awarded to each item (never score 0 and most of the time score 4). Phrases 4-5-6-7-10 and 13 are scored inversely (never score 4 to most of the time score 0). Then, by collecting the items, the overall score is 0-56, which the higher score indicates more perceived stress (34). Eating behavior will be measured using three-factor eating questionnaire at the beginning and the end of the study. The questionnaire consists of 18 questions in 3 sections about cognitive factors related to eating, hunger and emotional eating. The questionnaire is scored by questions 1 to 13 on a four-point Likert scale from one (definitely incorrect) to four (definitely correct). Questions 14 to 17 also have a separate Likert scale, and question 18 has an 8-degree Likert scoring scale. The higher rating in the cognitive factors associated with eating indicates greater limitation in receiving calories to control body weight. Also, higher hunger score indicates a person's greater susceptibility to eating in response to hunger and higher emotional eating score indicates a person's greater susceptibility to excessive eating. The validity of this questionnaire has been measured in Iran (35).
In order to measure blood biochemical parameters 5 cc of venous blood samples will be taken from the site of the bracing vein and after 12 to 14 hours fasting by the laboratory technician at the beginning and the end of the study. Blood samples taken in tubes containing sodium citrate anticoagulants will be collected and centrifuged in the laboratory of the Shahid Beheshti Nutrition Faculty for 15 minutes at a speed of 500 round per minute and serums will be stored at -80°C until the tests are performed. Serum levels of BDNF and LBP will be measured by ELISA method with human BDNF kit (PadginTeb, under the license of Zelbio, Iran) and human LBP kit (PadginTeb, under the license of Zelbio, Iran) with the intra-assay and inter- assay CV of < 10% and <12%, respectively for both kits in the laboratory of the Nutrition Institute of Shahid Beheshti University of Medical Sciences.
Assessment of dietary intake
In this study, to assess participant’s dietary intake, at the beginning of the study, at the end of the fourth and eighth weeks of the study, three days of dietary recall about one weekend day and two week days will be completed through face-to-face or telephone interviews. Common household measurement tools (glass, cup, soup bowl, plates, teaspoon and tablespoon) will be provided to assist subjects in estimating the portion size of the food. Dietary intake will be analyzed using Nutritionist IV (N4) software.
Assessment of physical activity level
Physical activity questionnaire will be completed for them at baseline and week 8 (33). This questionnaire is divided into 9 levels based on the intensity of physical activity and metabolic equivalents (MET) and its rows are adjusted from top to bottom from inactivity (MET = 0.9) to intense activities (MET >6). The intensity of activities from top to bottom is 0.9, 1, 1.5, 2, 3, 4, 5, 6 and above 6, respectively. These numbers are multiplied by the duration of the activity to show the intensity of the activity performed per time unit (MET.time).
Statistical analysis
In this study, data analysis will be performed by using SPSS version 21.0 (SPSS Inc, Chicago, Illinois) software. Paired t test will be used to compare the mean of quantitative variables with normal distribution in each group between the beginning and the end of the study and the t test will be used to compare their mean between the two groups at the beginning and end of the study. In the case of quantitative variables with non-normal distribution, Wilcoxon and Mann-Whitney tests are used, respectively. In case of the variables measured three times during the study (beginning, fourth week and eighth week), repeated ANOVA test will be used. Covariance analysis will be used to eliminate the effect of quantitative confounding factors. Quantitative confounding factors are physical activity and baseline values of the biochemical markers. Chi-square test will be used to compare the qualitative variables between the two groups and regression analysis is used to eliminate the effect of qualitative confounding.
Plans for auditing trial conduct
There will be unplanned checks on the quality of the data or the progress of the trial.
Ethical considerations
Women with overweight/obesity and food addiction who meet the inclusion criteria will be completely informed about the protocol of the study. The protocol of this study was approved by ethics committee of Shahid Beheshti University of Medical Sciences and is in conformity with the declaration of Helsinki (approved number IR.SBMU.NNFTRI.REC.1399.03).
Protocol amendments
Any modifications to the protocol which may impact on the conduct of the study, potential benefit of the patient or may affect patient safety, including changes of study objectives, study design, patient population, sample sizes, study procedures, or significant administrative aspects will require a formal amendment to the protocol. Such amendment will be agreed upon by NNFTRI (National Nutrition and Food Technology Institute) and approved by ethics committee of Shahid Beheshti University of Medical Sciences prior to implementation. Administrative changes of the protocol are minor corrections and/or clarifications that have no effect on the way the study is to be conducted. These administrative changes will be agreed upon by NNFTRI. The ethics committee of Shahid Beheshti University of Medical Sciences may be notified of administrative changes at the discretion of NNFTRI.