The article reviews the effects of intermittent fasting (IF) and periodic fasting (PF) on health and disease processes in both laboratory animals and humans. IF involves extended periods of food deprivation followed by normal food intake, while PF includes longer fasting periods lasting from 2 to 21 days or more. Studies in laboratory rats and mice have shown that IF and PF have beneficial effects on various health indicators and can counteract age-related disorders such as diabetes, cardiovascular disease, cancers, and neurological disorders. In humans, IF and PF have been shown to improve weight loss, insulin resistance, and reduce risk factors for cardiovascular disease. The cellular and molecular mechanisms underlying these effects involve adaptive cellular stress response signaling pathways that enhance mitochondrial health, DNA repair, and autophagy. However, more randomized controlled clinical trials are needed to establish the efficacy of IF in improving general health and preventing major diseases of aging. The article also discusses the potential benefits of IF in treating age-related diseases, including diabetes, cardiovascular disease, neurological disorders, and cancer, and highlights the need for further research to understand the mechanisms and optimize the protocols for IF.The article reviews the effects of intermittent fasting (IF) and periodic fasting (PF) on health and disease processes in both laboratory animals and humans. IF involves extended periods of food deprivation followed by normal food intake, while PF includes longer fasting periods lasting from 2 to 21 days or more. Studies in laboratory rats and mice have shown that IF and PF have beneficial effects on various health indicators and can counteract age-related disorders such as diabetes, cardiovascular disease, cancers, and neurological disorders. In humans, IF and PF have been shown to improve weight loss, insulin resistance, and reduce risk factors for cardiovascular disease. The cellular and molecular mechanisms underlying these effects involve adaptive cellular stress response signaling pathways that enhance mitochondrial health, DNA repair, and autophagy. However, more randomized controlled clinical trials are needed to establish the efficacy of IF in improving general health and preventing major diseases of aging. The article also discusses the potential benefits of IF in treating age-related diseases, including diabetes, cardiovascular disease, neurological disorders, and cancer, and highlights the need for further research to understand the mechanisms and optimize the protocols for IF.