Identifying hyponutrition is essential at the hospital setting to avoid or minimize the impact on the patients' clinical course and its association with more severe complications, longer hospital staying, and increased mortality, and all of this is associated with increased costs for the institution and the society. The aims of this study were to disbelieve the epidemiology of hospital hyponutrition, the types of hyponutrition, the body response to fasting, the clinical course of the patient with hyponutrition and the consequences of hyponutrition in the different live stages and, thus, we carried out a review on hospital hyponutrition. We found that hyponutrition prevalence is high in the hospital setting, hyponutrition influences genetic, metabolic, and hormonal factors of the human being and leads to harmful effects from the intrauterine fetal development until the adulthood. There are also different types of hyponutrition, the differentiation being important to decide the best therapy. We also found that hyponutrition is related to inflammation. When inflammation is chronic and mild to moderate (such as in organ failure, pancreatic cancer, obesity, rheumatoid or sarcopenic arthritis), the term "hyponutrition-related chronic disease", and when inflammation is acute and severe (severe infection, burns, trauma or head trauma), the preferred term is "hyponutrition-related acute disease or hyponutrition-related lesions". Finally, the patient with hyponutrition has worse clinical course than the patient with an appropriate nutritional status.