Intermittent fasting - its benefits and risks

Background: Intermittent fasting (IF) is a dietary approach increasingly studied for its potential benefits in metabolic regulation, hormonal balance, and the prevention or management of chronic diseases. It includes several protocols such as alternate-day fasting (ADF), time-restricted feeding (TRF), the 5:2 method, and periodic fasting. These regimens differ in fasting–feeding cycles and may influence weight loss, insulin sensitivity, lipid metabolism, and disease progression through mechanisms involving hormonal modulation, reduced inflammation, and enhanced autophagy. The aim of this review is to evaluate the efficacy and mechanisms of these IF protocols, with a focus on their metabolic, endocrine, and disease-specific outcomes. Aims: The aim of this study is to examine the efficacy and mechanisms of the following IF protocols: alternate-day fasting (ADF), time-restricted feeding (TRF), the 5:2 method, and periodic fasting. The study focuses on their metabolic, endocrine, and disease-specific outcomes. Methods: A literature search was conducted in PubMed, Scopus, and Google Scholar for peer-reviewed studies evaluating the effects of IF on metabolic, endocrine, and disease-specific outcomes. Inclusion criteria comprised studies with clearly defined IF protocols and measurable endpoints such as changes in body weight, fat mass, lean mass, insulin sensitivity, lipid profiles, hormonal markers, and disease-related outcomes. Human studies were prioritized over animal data where available. Results: The evidence indicates that IF can reduce body weight, fat mass, and insulin resistance while preserving lean mass. Additional benefits include improved lipid profiles, decreased systemic inflammation, and enhanced autophagy. These effects may contribute to lowering the risk or slowing the progression of type 2 diabetes, cardiovascular disease, cancer, and Alzheimer’s disease. Comparative data suggest that in the long term, IF may be as effective as continuous calorie restriction, with patient adherence and individual health status being key determinants of success. Conclusions: Intermittent fasting is an effective dietary strategy with potential to improve metabolic flexibility and reduce the risk of chronic diseases. However, its application should be individualized, taking into account comorbidities, genetic variability, and lifestyle factors. Further long-term, high-quality clinical trials are required to refine protocols, assess safety, and compare outcomes with other dietary strategies across diverse populations.