Effects of Different Dietary Models on Eating Behavior and Obesity Management in Overweight and Obese Individuals: A Randomized Controlled Trial

Overweight and obesity are among the most significant risk factors for health globally, with more than 1 billion people expected to be obese by 2030. Turkey is projected to be among the countries at high risk of obesity by 2030. Furthermore, obesity is among the preventable risk factors for cardiovascular disease (CVD), cancer, diabetes, stroke, and chronic lung disease, among other noncommunicable diseases (NCDs). Overweight and obesity are widespread and increasing health problems worldwide. Excessive adiposity is associated with insulin resistance, lipid deterioration, and systemic inflammation. A 5-10% weight loss is known to improve metabolic outcomes such as blood sugar, lipid profile, and blood pressure. Individuals employ a variety of strategies to lose weight. Lifestyle interventions that encourage calorie restriction and increased physical activity are the most commonly prescribed interventions by healthcare and clinical practitioners. While continuous energy restriction is a more traditional method for reducing energy intake, intermittent fasting has emerged as a potential alternative in the last decade. Fasting is known as one of the world's oldest traditions and is practiced across various communities for cultural or religious reasons. Fasting has also been used as a treatment for illness in the past. Hippocrates, considered the father of modern medicine, emphasized the importance of fasting during illness with the saying, "Eating when you are sick is feeding your illness." Intermittent fasting (IF), or periods of voluntary abstinence from food and drink, is an ancient practice followed in various forms by many populations worldwide. Intermittent fasting involves fasting or restricting food intake for specific hours of the day or on specific days of the week. IF can be implemented in three different ways: alternate-day fasting, the 5:2 diet, and time-restricted feeding (TRF). Alternate-day fasting involves alternating days of food and drink consumption with days of fasting during which no energy-containing food or drink is consumed. In alternate-day fasting, approximately 20-25% of energy needs are met on fasting days. Modified fasting is also known as the 5:2 method. This eating pattern involves a very low-calorie diet for two non-consecutive days per week, followed by normal energy requirements without energy restriction for the other five days. Another approach, time-restricted feeding (TRF), is used to describe an eating pattern in which food intake is restricted to a time window of 8 hours or less each day. Among intermittent fasting diets, the TRF diet is a lifestyle intervention that restricts food intake to a fixed number of hours. Welton and colleagues reported that the ideal fasting period for positive weight change is 16 hours. In recent years, small-scale human studies demonstrating the importance of time-restricted eating have become widespread. Many of these studies, as in animal studies, have demonstrated the beneficial effects of intermittent fasting on human metabolism. TRF has been found to reduce energy intake, body weight, body fat, blood glucose, triglycerides, glucose tolerance, and inflammatory markers. It has been established that IF may be beneficial in reducing body weight, improving insulin resistance, and reducing infection by regulating circadian rhythms, gut microbial composition, and metabolism. Time-restricted eating has been suggested as a potential weight-loss strategy because it may be more acceptable due to the reduced burden of dietary restriction. Intermittent fasting reduces body fat storage and increases fat mobilization, oxidation, and ketone body production, resulting in weight loss. A study comparing intermittent fasting with low-energy diets found that, although body weight reductions were similar after three months of follow-up, the reduction in fat mass was greater in the intermittent fasting group.

The term "Mediterranean diet" reflects the food combinations typical of Mediterranean populations such as Greeks, Southern Italians, and Spaniards in the early 1960s. Lower rates of cardiovascular disease (CVD) and chronic diseases associated with aging in these populations led to its popularization. Since November 2010, the Mediterranean diet has been included on the list of the Intangible Cultural Heritage of Humanity by UNESCO, as it represents a heritage closely linked to cultures and lifestyles passed down through centuries and is the result of the complex socioeconomic development of Mediterranean populations.

Eating behavior changes from birth onward, depending on many factors. Eating, which is essential for life, can, in some cases, develop into a psychiatric disorder, or differences from normal eating behaviors can occur. Eating is not an automatic process, especially for young people. It is significantly influenced by the cultural, social, and psychological pressures individuals feel. In recent years, various theories have been developed to assess behaviors that can impair eating motivation, adequate food intake, and body weight control. "Emotional eating" refers to eating to cope with negative emotions and relieve stress by ignoring satiety signals without internal physiological hunger signals. "External eating" refers to eating in response to stimuli related to food consumption, regardless of hunger and satiety signals. "Restrictive eating" reflects the degree to which one deliberately restricts food intake.

Today, the prevalence of non-communicable diseases is increasing, and obesity is among the risk factors for these diseases. While many methods are used in the treatment of obesity, the role of medical nutrition therapy is crucial. Various methods are used in medical nutrition therapy for obesity. These methods include the calorie-restricted Mediterranean diet, the time-restricted eating model (a type of intermittent fasting), and standard dietary intervention. This study will evaluate the effects of these dietary models on individuals' body composition, dietary intake, and eating behaviors.