Effect of Meal Frequency on Diet Self-Efficacy and Perceived Stress in Women With Weight Cycling

The study was conducted on women aged 25-55 who voluntarily applied to a dietary counseling office, met the inclusion criteria, had a BMI between 25 and 35 kg/m², and experienced weight fluctuations. In the analysis conducted to determine the sample size, the effect size was f = 0.204, the Type I error level was α = 0.05, the test power (1-β) was 0.95, and measurements were taken at 6 time points (0, 2, 4, 6, 8 Weeks and 6 months after the intervention ended), inter-measurement correlation r = 0.50, and the non-sphericity correction ε = 1. Under these conditions, the required total sample size was determined to be 41; considering the anticipated 20% participant attrition during the study, it was determined that at least 49 participants were needed, and to obtain more accurate data, it was planned to include at least 52 participants; the study was completed with a total of 59 participants. The intervention phase of the study lasted 8 weeks for each participant. During the intervention period, face-to-face interviews were conducted every 2 weeks, and all measurements within the scope of the study were repeated. Following the completion of the 8-week intervention, no further intervention or follow-up was conducted, and participants' ability to maintain their weight loss was assessed via a single follow-up measurement 6 months later. In accordance with the recommendations, a weight-loss diet was planned and implemented for each participant, reducing daily energy intake by 500-700 kcal to facilitate a weight loss of 0.5-1.0 kg per week; A weight-loss diet appropriate for the women's age and energy and nutrient requirements was planned, and two groups were formed using a simple randomization method. Group 1 followed a meal plan consisting of 3 main meals, while Group 2 followed a meal plan consisting of 3 main meals and 3 snacks. Written and verbal informed consent was obtained from all participants via the "Informed Consent Form." At the beginning of our study, a general information form, a three-day food consumption record, the International Physical Activity Questionnaire Short Form (IPAQ SHORT FORM), the Perceived Stress Scale (PSS), the Dietary Self-Efficacy Scale (DESS), and the General Well-Being Scale Short Form (GWBS-SF) were used. At the 8th week, when the intervention ended, and at the 6-month follow-up, the Perceived Stress Scale (PSS), Dietary Self-Efficacy Scale (DESS), and General Well-Being Scale Short Form (GWBS-SF) were repeated. Anthropometric measurements and body composition analyses conducted as part of the study (body weight, height, BMI, waist-to-height ratio, waist circumference, hip circumference, neck circumference, waist-to-height ratio waist-to-hip ratio, total body fat (kg and %), lean body mass (kg and %), body water (L ), basal metabolic rate (kcal)) were performed at weeks 0, 2, 4, 6, and 8, as well as 6 months after the intervention ended. Anthropometric measurements were taken using standard measurement techniques, while body composition analyses were performed using the INBODY 270 device. Anthropometric indices (Lipid Accumulation Product Index - LAP, Visceral Adiposity Index - VAI, Conicity Index - CI, Body Shape Index - ABSI, Abdominal Volume Index - AVI, Body Adiposity Index - BAI, Body Roundness Index - BRI, Anthropometric Risk Index - ARI) calculated using validated formulas based on anthropometric measurements and relevant biochemical parameters. Participants' biochemical test results were used to develop individualized dietary plans and to observe changes in biochemical findings during the weight loss process. No new blood tests were requested from the participants in this study. The biochemical data used in the study (fasting blood glucose, triglycerides, total cholesterol, HDL-C, LDL-C, TSH, ALT, AST, HbA1c) were obtained from laboratory results recorded in the participants' health records and dating back to the past 3 months. Note: This trial was retrospectively registered. Data collection was completed prior to registration in ClinicalTrials.gov.