Quantifying the impact of intermittent fasting on appetite
Intermittent fasting (IF) is an eating pattern that involves cycling between periods of fasting and eating. It has gained popularity for its potential effects on various aspects of health, including appetite regulation. Here are some key points regarding the impact of intermittent fasting on appetite:
Changes in Hunger Hormones: Intermittent fasting may affect the release and regulation of appetite hormones. Research suggests that fasting periods can lead to changes in the levels of hormones such as ghrelin (the hunger hormone) and leptin (the satiety hormone). These hormonal fluctuations may impact feelings of hunger and fullness.
Adaptation to Fasting: Over time, individuals practicing intermittent fasting may experience a change in their appetite patterns. Some studies have shown that the body can adapt to fasting, and hunger levels may decrease during fasting periods. This adaptation is believed to be related to shifts in hormonal signaling and metabolic adjustments.
Meal Timing and Control: Intermittent fasting typically involves time-restricted feeding, where individuals consume their meals within a specific window of time. This restricted eating window may help improve meal control and reduce snacking or excessive calorie intake. By limiting the duration of eating, individuals may have better control over their overall calorie consumption.
Impact on Food Preferences: Intermittent fasting may influence food preferences and choices. Some studies suggest that fasting periods can lead to changes in taste perception, cravings, and the desire for high-calorie foods. However, individual responses can vary, and more research is needed to fully understand these effects.
Psychological Factors: It is important to consider psychological factors when assessing the impact of intermittent fasting on appetite. Fasting periods may elicit feelings of deprivation, which can influence perceived hunger levels and psychological responses to food. Adherence to an intermittent fasting regimen and individual attitudes towards fasting may affect appetite experiences.
Individual Variability: It is worth noting that responses to intermittent fasting can vary among individuals. Factors such as age, sex, body composition, and metabolic health may influence how individuals respond to fasting in terms of appetite regulation. Some individuals may find it easier to adhere to an intermittent fasting schedule, while others may struggle with increased hunger during fasting periods.
Results
Initially, 4,390 studies were identified, from which 1,590 duplicate records were removed, and 2,800 records underwent abstract and title screening, following which 2,430 studies were excluded, and the complete text of 370 studies was analyzed.
After excluding 251 studies not measuring appetite, 20 non-RCT studies, 59 studies lacking the CER comparator, nine lacking the IF intervention, and seven ongoing RCTs, 17 studies were considered for the final analysis.
The RCTs comprised 1,111 adults practicing IF or CER over two weeks to one year with BMI values equal to or greater than 24.0 kg/m2. The team found no significant evidence of IF affecting hunger [weighted mean difference (WMD) −3.0], fullness (WMD 3.1), desire to eat (WMD −3.9), or PFC (WMD −2.8) differently than CER interventions.
Similar results were obtained in the subgroup analysis for the different types of IF regimes. Among the included studies, four RCTs had medium bias risks, whereas 13 had high risks. Appetite measurement varied across studies, and the quality of evidence was very low for fullness, hunger, desire to eat, and PFC.
In the sensitivity analysis, the direction of effect was the same; however, the fixed-effects meta-analysis findings showed that IF increased fullness, reducing the desire to eat, compared to CER interventions.
High bias risks may be due to the nature of dietary interventions. It may not often be possible to blind participants or those delivering the health intervention, which could introduce expectation bias in the intervention group.
Moreover, appetite was evaluated using self-reported data. The wide variations in caloric limitation protocols and their effects (for example, varied daily caloric intake) could also influence the study findings.
Conclusion
Overall, the study findings indicated that intermittent fasting does not mitigate an increase in our appetite that is often linked to continuous energy restriction, with no reduction in fullness, hunger, eating desire, or PFC.
The findings contrast those reported in previous studies, likely due to differences in the analysis approach.
Further research could include momentary ecological assessments to evaluate fluctuations in appetite throughout the day and subtle appetite modifications related to IF interventions.
It is important to approach intermittent fasting with caution and consider individual needs and goals. Consulting with a healthcare professional or registered dietitian is advisable before starting an intermittent fasting regimen, especially for individuals with specific health conditions or dietary requirements.
Furthermore, research on the long-term effects and sustainability of intermittent fasting is still evolving. While some studies suggest potential benefits, more research is needed to fully understand the impact of intermittent fasting on appetite regulation and its overall effects on health and well-being.
