IGF1 and nutritional deficiency disease: In recent years, results from studies aiming to find a link between metabolism and aging demonstrated that CR, defined as a reduction in calorie intake below usual ad libitum intake without malnutrition, caused metabolic and molecular modifications in components of the nutrient-sensing and stress-responsive pathways, such as GH/IGF-I signaling, mTOR pathway, adenosine 5′-monophosphate–activated protein kinase (AMPK), forkhead box protein O (FOXO), sirtuins, and nuclear factor erythroid 2-related factor 2 (NRF2) [308,309,310,311].