Effect of Intermittent Fasting and Mediterranean Diet on Body Composition and Nutritional Intake

The Mediterranean diet, based on the nutritional patterns of people living in the Mediterranean region, has been found to have a different dietary style and may be effective against CHD and many other diseases. The Mediterranean diet is a model based on a high ratio of monounsaturated and saturated fats, high consumption of legumes, high consumption of fruits and vegetables, low consumption of meat and meat products, and moderate consumption of milk and dairy products. It is thought that the Mediterranean diet can be effective both in preventing diseases and in managing the disease process. In addition, the Mediterranean diet has been used in calorie-restricted diet models due to its effect on obesity and body composition. When the studies in the literature are examined; in a meta-analysis, weight loss was observed in Mediterranean diet models with energy restriction. In an intervention study based on the Mediterranean diet model in obese patients with metabolic syndrome, significant changes occurred in BMI, total fat percentage, total lean mass percentage, and abdominal fat percentage. Another study showed statistically significant changes in body weight and BMI in individuals who underwent Mediterranean diet intervention. Along with this change in body weight, the group with more than 5% weight loss showed a decrease in total cholesterol and triglyceride levels and values such as HOMA-IR in blood parameters. Furthermore, another meta-analysis found that some studies showed that the Mediterranean diet significantly reduced the likelihood of overweight/obesity, supported weight loss, or caused greater weight loss than the control diet, while other studies found no significant association between the Mediterranean diet and overweight/obesity.

Fasting is known as one of the oldest traditions in the world and is practiced among various communities for cultural or religious reasons. Fasting has also been used in the past as a method of treating illnesses. Hippocrates, considered the father of modern medicine, emphasized the importance of fasting during illness with his statement, "To eat when you are sick is to feed your illness". Intermittent fasting, that is, periods of voluntary abstinence from food and drink, is an ancient practice followed in different forms by many populations worldwide. Intermittent fasting involves fasting or restricted eating at certain times of the day or on certain days of the week. Alternate-day fasting involves alternating days when food and drinks are consumed with days when energy-containing foods or drinks are not consumed. In alternate-day fasting, approximately 20-25% of energy requirements are met on fasting days. Modified fasting is also known as the 5:2 method. This dietary model involves a very low-calorie diet on 2 non-consecutive days of the week, and normal energy requirements without energy restriction on the other 5 days. Another approach is time-restricted eating, which is used to describe an eating pattern where food intake is limited to a time window of 8 hours or less each da. Welton et al. 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-ricted eating have become widespread. Most of these studies, as in animal studies, have revealed the beneficial aspects of intermittent fasting in human metabolism. With time-restricted eating, reductions in energy intake, body weight, body fat, blood sugar, triglycerides, glucose tolerance, and inflammatory markers have been observed. Among fasting methods are religious fasts, such as Ramadan, which allow eating after sunset and before dawn. Since the fasting and eating periods last approximately 12 hours and the amount of energy given is not limited, it is a type of time-restricted eating.

Intermittent fasting, which has become a popular topic recently, is an alternative energy restriction method. Time-restricted eating, alternate-day fasting, the 5:2 diet, and Ramadan fasting are the most frequently used fasting protocols in the literature. Although daily energy restriction is the most commonly used diet model for achieving weight loss and improving body composition and metabolic health, intermittent fasting practices have become a focus of interest in recent years.

A review of studies in the literature revealed statistically significant differences in pre- and post-intervention body weight and BMI in 33 adults who underwent an 8-hour time-restricted feeding model for four weeks. A randomized controlled trial of 16 men and women (BMI 20-39 kg/m²) conducted over 10 weeks examined changes in body composition between the intervention and control groups using a time-restricted feeding model without energy restriction. According to Liu et al., no significant differences were found between the experimental and control groups in terms of reduction in body weight, body fat, or metabolic risk factors in obese individuals who underwent a time-restricted feeding model. A significant decrease in body fat percentage was observed in the time-restricted feeding model compared to the control group, while there was no significant change in body weight in either group. In another study, 101 overweight and obese adults were randomized into an alternate-day fasting group (n=34), a 16/8 time-restricted feeding group (n=33), and a control group (n=34). In the alternating-day fasting and 16/8 time-restricted eating groups, reductions in body weight, body mass index, and waist circumference were found to be more significant compared to the control group. Furthermore, the reductions in body weight and BMI in the alternating-day fasting group were more significant than those in the 16/8 group. In another randomized controlled trial of 40 obese young people aged 18-25, the intervention group underwent a 5:2 intermittent fasting diet, while the control group continued their previous eating habits. After a four-week intervention, the group undergoing 5:2 intermittent fasting showed a statistically significant decrease in energy intake and BMI compared to the control group. In contrast, Witjaksono et al. monitored weight loss in 50 obese participants using a 5:2 modified diet model (n=25) and a control group (n=25). While there were no significant changes in fat mass, lean mass, skeletal muscle, and BMI between the groups, reductions in carbohydrate, protein, and fat intake were statistically significant in both groups.

In conclusion, the prevalence of noncommunicable diseases is increasing today, and obesity is among the important risk factors for these diseases. While many methods are used in the treatment of obesity, medical nutritional therapies are also important. Different methods are used in medical nutritional therapies for obesity, including calorie-restricted Mediterranean diets and time-restricted eating models, which are one of the intermittent fasting models. This study aimed to examine the effect of dietary models on body composition and dietary intake in the management of obesity.