Cessation of Discontinuous Fasting and Weight Loss

Explore the benefits of intermittent fasting and its impact on metabolism. Discover the appropriate number of meals per day and how to establish the eating window. Learn the basics of TRF and find out more about the influence of intermittent fasting on body weight reduction.

Intermittent fasting constitutes a diet that relies on incorporating full or partial fasting periods of varying length and frequency.

Every alternate day, the provision of less than 25% of daily caloric requirement.

Restriction of food intake to a designated time span throughout the day, the so-called food window. Depending on which part of the day the window covers, it is distinguished: - early-day TRF – window ends before 18:00 - mid-day TRF – window ends after 18:00.

Conducting fasting periods of an average duration of 24 hours 1–2 times a week.

The recent fascination with the positive effects of intermittent fasting is captivating, considering that research over the years has indicated a beneficial impact on body weight, carbohydrate, and lipid metabolism from consuming 3 or more meals per day. P. Fabry et al. demonstrated that among men aged 60-64 who consumed 3 meals or less, there was a significantly higher incidence of overweight, hypercholesterolemia, and irregular glucose tolerance compared to those who ate 5 or more meals per day. S. L. Edelstein et al. studied over 2,000 residents of Rancho Bernardo in California, aged 50-89, both male and female. They too observed lower levels of LDL cholesterol in individuals who consumed more than 4 meals per day. How can this trend be explained? Perhaps the key lies in the fact that when we consume smaller, more frequent meals, blood glucose levels, and consequently, insulin levels can reach lower levels than when consuming larger, higher-glucose meals. Insulin, which is stimulated by glucose, activates the key enzyme for cholesterol synthesis, HMG-CoA reductase. Insulin also inhibits the activity of lipase, an enzyme that breaks down fats. This suggests why studies also indicate a link between the number of meals and body weight. According to a study published at the beginning of the 20th century by Y. Ma et al., the likelihood of obesity was significantly lower in the group that consumed 4 or more meals compared to the group that ate 3 or fewer meals per day. A 16-year observation of over 29,000 Americans (male healthcare workers) participating in The Health Professionals Follow-Up Study showed that the risk of developing type 2 diabetes was significantly higher in those who skipped breakfast or consumed 1-2 meals per day compared to those who consumed 3 or more meals. The question arises as to whether the results of these and similar studies can be applied to the general population and if they reflect reality. F. Bellisle et al. note that while many studies do not show any relationship between the number of meals and body weight, those that do show a consistent trend (more meals = lower body weight). So, how does intermittent fasting actually affect body weight and metabolism?

C. A. Rynders et al. summarize the results of 11 human studies comparing the effect of PF on body weight with the traditional reduction diet, or TDR (limited daily calorie intake, 3-5 meals per day). The effectiveness of IF was comparable to TDR. Different variants of restriction were used, such as: reducing dietary calories to 25% of normal intake for 2 days per week and eating to satiety for the remaining 5 days, complete restriction for 2 days per week (unrestricted eating on remaining days), reduction to a specific calorie amount, such as 1700 kcal for women for 2 days per week. It is worth noting the study by J. F. Trepanowski et al., which involved 100 participants who were divided into 3 groups: 1. the group that was restricted to 25% of daily requirements every other day; 2. the group that reduced daily calories to 75% of requirements; 3. the control group. The weight loss in groups 1 and 2 was practically the same. However, the LDL cholesterol level increased in the participants of group 1. More people from this group dropped out during the study compared to group 2. Furthermore, the participants of group 1 ate more than recommended on restriction days and less than recommended on the remaining days. This may indicate that this type of eating is more difficult in the long-term implementation.

Unfortunately, no studies have been conducted that systematically compared the effectiveness of TRF with the effectiveness of TDR. However, the sole implementation of TRF can bring benefits. S. Gill and S. Panda recommended to several obese individuals, whose dietary window lasted 14 hours during the day, to shorten it to 10-12 hours. The time limitation for consuming meals caused the participants to eat less (about 20%). Similarly, participants in the pilot study R. Anthony et al. who did not change their daily diet except for shifting meals – started eating them later in the day, and the last participants ate them by 1.5 hours earlier. A reduction of fat tissue in the intervention-treated participants was also demonstrated.

The ancient proverb says, eat breakfast like a king, share lunch with a friend, and give dinner to your enemy. More in the morning, or maybe in the evening? How to eat? Similar conclusions are drawn by some researchers, such as D. Jakubowicz et al. or H. Kahleova et al., who have shown that eating more calories in the first half of the day during the day protects against weight gain. However, as the day progresses, the cholesterol level decreases, i.e., each subsequent meal stabilizes the body's metabolic processes less. The total conversion rate decreases over time. It is also crucial to place the feeding window on the 24-hour time axis. E. F. Sutton et al. point to conflicting results of mid-day TRF studies. Some of them even suggest that mid-day TRF may impair pancreatic function and negatively affect the lipid profile. On the other hand, early TRF leads to weight loss, improves carbohydrate metabolism, and lipid metabolism. It turns out that probably not only weight reduction affects the effectiveness of TRF. E. F. Sutton et al. have shown that in men with carbohydrate metabolism disorders, an isocaloric feeding window model was implemented from 7:00 to 15:00. After this time, the subjects ate no meals. Although they did not lose weight, after 5 weeks, a lower insulin level was observed in them, as well as a better response of the beta cells of the pancreas and a reduction in insulin resistance. In addition, blood pressure values decreased, but the cholesterol level remained unchanged. It is worth noting that TRF was associated with a reduction in appetite in the evening hours.

C. A. Rynders and colleagues also reviewed studies on the impact of intermittent and periodic fasting on the risk of heart disease. The analysis showed that they had no greater effect on glucose levels, cholesterol, or insulin resistance compared to a traditional weight loss diet.

J. Rothschild et al. conducted a review of studies evaluating the relationship between TRF use and changes in lipid profile compared to ADF and PF. While the results were inconsistent, some studies showed a decrease in LDL cholesterol levels after using a nutritional window (7-8 hours and 10-12 hours). The authors highlighted that TRF may be more effective in regulating lipid and carbohydrate metabolism than the changes associated with ADF and PF. The reason for this could be the higher frequency of fasting periods in TRF, which occur almost daily, in contrast to ADF and PF, where they are less frequent. There are still many unanswered questions, and further studies are needed to confirm the effectiveness of TRF in preventing and treating metabolic disorders and reducing body weight. The application of TRF can be difficult to maintain over a longer period. M. C. Stockman and colleagues noted that in studies, it is particularly the individuals in the TRF groups who more frequently withdraw from experiments due to the burden of the intervention than those in the TDR groups. M. N. Harvie and colleagues also pointed out that TRF may lead to binge eating, especially in people with eating disorders. At present, it is difficult to evaluate this type of nutrition.

At present, intermittent fasting (IF) may not be generally recommended as a means of improving health, but time-restricted feeding (TRF) may be beneficial in weight reduction. Some individuals may benefit from the introduction of several guidelines: avoiding eating in the evening and at night, shortening the eating window to at least 10 hours, consuming the majority of daily calories in the first half of the day.