The effects of intermittent fasting on the body composition and biochemical parameters in adults: A prospective observational study

Objective: The prevalence of obesity and obesity-related diseases is increasing all over the world. Diet changes for weight loss of obese and overweight patients should be planned out and followed up by health care providers. Current guidelines recommend calorie-restricted three meals and three snacks regimen for the dietary treatment of obesity. However, as there are various problems related to diet compliance and long-term weight maintenance in calorie-restricted three meals and three snacks diets, alternative approaches are needed. Time-restricted eating variant of intermittent fasting can prove to be an option for the dietary treatment of obesity. Before time-restricted eating can be routinely recommended to patients, more empirical evidence through scientific studies is required. Family physicians, the first point of contact with the healthcare system of patients as primary care physicians, are actively at the forefront of the fight against obesity by providing personalized, comprehensive and holistic care. This study was planned to present time-limited eating, which is easily explained and applicable to suitable patients in the fight against obesity and obesity-related diseases within the environment of family medicine, as an alternative treatment to three meals and three snacks diet. Materials and Methods: This study was carried with participants who applied to one of the family health center between the dates of 01.11.2021 and 01.07.2022, aged 18 to 65, with a BMI>25 kg/m2, and who met the criteria for being part of the study, after accepted the terms thereof and voluntarily signed the informed consent form. The sample analysis required that 126 patients participate in the study, of which 63 would be in the three meals and three snacks group, and 63 in the time-restricted eating group. 174 patients were included in the study, but 37 patients could not complete it for various reasons. The study was concluded with the participation of 137 patients. Diet lists with a 400-500 kcal calorie deficit in relation to their calculated total energy expenditure with similar nutritional compositions were prepared. 88 patients were included in the 16:8 time-restricted eating group, and 86 were included in the three meals and three snacks diet group. Participants' age, gender, smoking habits, alcohol use, education level and weekly sportive activity were inquired after; and their anthropometric measurements (weight, height, waist circumference, waist/height ratio, hip circumference), body composition, blood pressure were taken before the start of the study and at the end of the 8-week period. Again, their complete blood count, pre-prandial blood glucose, ALT, AST, total cholesterol, HDL, LDL, triglyceride, HbA1c, creatinine, TSH, ferritin and CRP values were examined in blood samples taken in the morning after 8 hours of fasting before the study and after the 8-week period. Likewise, the eating attitude test scores and cardiovascular risk scores of the participants were calculated. At the end of the study, the desire of the people to continue the same diet and the number of days they did not follow it were asked. Before-and-after comparisons were made within the groups themselves and between the groups. While analyzing the data, Kolmogrov Smirnov test, Pearson Chi-squared test, Mann Whitney U test, Spearman Correlation test and Wilcoxon test were used, and only cases with a P-value below 0.05 were considered statistically significant. Results: Our study was concluded with 137 participants, 21 men and 116 women, of which 69 were in the time-restricted eating group, and 68 in the three meals and three snacks groups. There was no statistical difference as to how the gender, age, height, smoking, alcohol use, and the number of days where the diet was not followed were distributed between groups (p>0.05). In terms of education level, the ratio of undergraduate and graduate participants was statistically significantly higher in the intermittent fasting group (p=0.012). We have observed that the weight, BMI, waist circumference, hip circumference, waist-to-height ratio (WHtR), systolic blood pressure values, HbA1c, HDL, ALT, AST, body fat percentage, degree of obesity and metabolic age of the time-restricted eating group decreased statistically significantly when compared to the values before the two-month diet; and their CRP, body muscle percentage and body fluid levels increased statistically significantly (p<0.05). In the group that followed the three meals and three snacks diet, weight, BMI, waist circumference, hip circumference, waist/height ratio (WHtR), waist circumference*, waist/height ratio (WHtR)*, systolic blood pressure values, diastolic blood pressure values, HbA1c, HDL , LDL, total cholesterol, CRP, ALT, cardiovascular risk score, body fat percentage, degree of obesity and metabolic age decreased; while ferritin, body muscle percentage and body fluid levels were found to increase (p<0.05). When the parameters obtained between the groups were compared, it was observed that weight loss, decrease in BMI, decrease in waist/height ratio (WHtR)* ratio, and decrease in obesity degree were statistically higher in the time-restricted eating group compared to the group that ate three main meals and three snacks (p<0, 05). In the three main and three snack groups, the high decrease in LDL value gained statistical significance compared to the time-restricted eating group (p<0.05). The number of participants who wish to continue following the same dietary regimen was also statistically significantly higher in the time-restricted eating group (p<0.001). Conclusion: The results of our study support the previous literature and we have confirmed that time-restricted eating promotes weight loss, decrease in fat percentage, decrease in systolic blood pressure and has positive effects on metabolic parameters. It is significant that time-restricted eating is more advantageous than the three meals and three snacks diet for weight loss. Diverging from previous studies, we have observed a decrease in HDL levels in both groups when we examined the effects on HDL, LDL, total cholesterol and triglyceride values, but there was no statistically significant difference in this decrease between the two groups. In terms of reducing the LDL value, the three meals and three snacks diet group was statistically significantly more successful. In conclusion, both dietary approaches were found to be yielding positive results, and it has been observed that time-restricted eating is a good alternative to the three meals and three snacks diet in weight loss treatment. Time-restricted eating method can become a routine recommendation in the dietary treatment of obesity after being supported by longer-term and randomized controlled studies.