Objective: In this study, it was aimed to determine the effect of time-restricted feeding on anthropometric measurements and leptin, ghrelin, adiponectin, insulin and cortisol hormone levels in obese women.

Material and Methods: This study was carried out with women who voluntarily accepted to participate in the study who applied to the Baskent University Ankara Hospital Endocrinonogy Outpatient Clinic between September 2019 and October 2020. Women between the ages of 20 and 50, with a body mass index of 29-35 kg/m2, without any chronic disease, who did not have a weight loss diet in the last 6 months, and who had regular night sleep were included in the study. This study was planned as a randomized cross-over design for a total of 9 weeks. Two different dietary interventions, "time-restricted feeding" and "extended-time feeding", were applied to 4 weeks for each group and a week for wash-out period. Anthropometric measurements and hormone levels of individuals were evaluated at the beginning and end of the study.

This study was conducted on volunteers who applied to Başkent University Ankara Hospital Endocrinonogy Outpatient Clinic between September 2019 and October 2020. The study was conducted on women between the ages of 20-50 years, with a body mass index (BMI) between 29-35 kg/m2, sedentary lifestyle, working day shift, regular night sleep habits (bedtime 10:00-12.00 pm; waking time 06:00-08:00 am), without any chronic disease, no dieting history in the last 6 months. Women who were in menopause, with eating disorders, psychiatric illnesses, metabolic and chronic diseases were excluded in the study. As the cross over design study was planned which in the comparison of any quantitative measurement, it was found appropriate to work with at least 29 people in order to reveal a medium to large effect size with a 5% Type I error probability and 86% power probability within the knowledge of the literature. PASS Power Software 3.1.3 for power analysis software was used.A total of 30 women participated in the study. The individuals were randomly divided into 2 groups as Group I (n:15) and Group II (n:15). This study was planned to be a randomized study with a cross-over design for a total of 9 weeks. The study was a two-armed study and two different dietary interventions were applied to the groups: "Time-Restricted Feeding (TRF)" and "Extended-Time Feeding (ETF)". A 1-week washout period was given between two 4-week dietary intervention periods. Ten subjects withdrawn from the study after the first dietary interventon period. A total of 20 people completed the study .At the beginning of the study, a questionnaire (demographic characteristics, educational status, occupation, family history, eating habits and sleep patterns, etc.) was applied to all individuals participating in the study by face-to-face interview method.Since there is no standard definition of TRF, fasting/feeding periods vary. In this study, 12-hour fasting and 12-hour feeding period defined by Pureza et al. were taken as the TRF model. In the first 4-week arm of the study, Group I applied a time-restricted feeding program from sunrise to sunset; for Group II, an extended-time feeding program was suggested that allows them to eat at any time of the day. During dietary interventions, a weight loss diet was applied to the participants. The daily energy requirements of the participants were calculated individually to lose 5% of their initial weight and the distributions of macronutrients were 45-60% of total energy from carbohydrates, 10-20% as protein and less than 35% from fat. Before dietary interventions a 60-minute informative meeting was held by the researcher dietitian, in which the food portion and amount were explained by using the visual food catalog.Anthropometric measurement and body composition were assessed at the beginning and end of each intervention.Serum hormone levels were analyzed at Baskent University Ankara Hospital Biochemistry Laboratory. Blood samples were taken from the patients at the beginning of the study and at the end of each period.Qualitative variables are given as number (S) and percentage (%). Continuous variables (quantitative variables) obtained by measurement are given with mean and standard deviation (¬x̄ ±SD) values. The conformity of the data obtained from the measured quantitative variables to the normal distribution was evaluated with the "Shapiro Wilk Test". Chi-Square (Chi-Square) test was used to determine the relationship or difference between qualitative variables. At the beginning of the study, the "Independent Samples T Test" was used to compare the averages of some quantitative variables according to the diet. "Paired Samples T-Test (T-Test in Dependent Groups)" was used to evaluate the groups within themselves. The criterion of "effect size (d=effect size) obtained from the comparison of dependent/independent groups" was used to determine the degree of effect of dietary interventions on individuals' hormone levels and anthropometric measurements. "Pearson Correlation Coefficent" and "Partial Correlation Coefficent" after removing the initial body weight were used to determine the relationship between quantitative variables. P<0.05 was accepted as the level of significance in all statistical analyses. The data obtained according to the results of the study were evaluated with the SPSS 25 (Statistical Package for Social Sciences) statistical package program.

Inclusion Criteria:

• Women between the ages of 20-50 years
• Body mass index (BMI) between 29-35 kg/m2
• Sedentary lifestyle
• Working day shift
• Regular night sleep habits (bedtime 10:00-12.00 pm; waking time 06:00-08:00 am)
• Without any chronic disease
• No dieting history in the last 6 months

Exclusion Criteria:

• Women who were in menopause
• Having eating disorders
• Having psychiatric illnesses
• Having metabolic and chronic diseases