Background: The World Health Organization (WHO) classifies malnutrition as the biggest threat to public health worldwide, and this condition is observed in 20-60% of hospitalized patients. Malnutrition is a state of the body in which due to insufficient supply or incorrect absorption of essential nutrients, the body composition changes and the body's functions are impaired. Malnutrition is associated not only with reduced body mass index but also with obesity.
Summary: Obesity is defined as a paradoxical state of malnutrition, which despite excessive energy consumption is associated with a shortage of individual microelements. Deficiency or lack of homeostasis of essential micronutrients can significantly affect daily performance, intellectual and emotional state, but also the physical state of the body. Food deficiency can also contribute to further weight gain or the development of other metabolic diseases. Micronutrient deficiency may include not only incorrect dietary choices and insufficient access to nutrient-rich foods but also changes in the absorption, distribution or excretion of nutrients, and altered micronutrient metabolism resulting from systemic inflammation caused by obesity. An effective therapy method recommended for people with morbid obesity is bariatric surgery aimed at both weight loss and improving quality of life. Unfortunately, the effects of these treatments are often medium- and long-term complications associated with micronutrient deficiency as a result of reduced consumption or absorption. Therefore, the use of bariatric surgery in patients with extreme obesity can affect the metabolism of microelements and increase the risk of nutritional deficiencies. Key Messages: Studies by many authors indicate a higher incidence of food deficiency among people with excessive body weight, than in people with normal body weight of the same age and same sex. Monitoring the concentration of minerals and vitamins in blood serum is a good practice in the treatment of obesity. The proper nutritional status of the body affects not only the state of health but also the effectiveness of therapy. The aim of the review was to present the issue of malnutrition in the context of obesity.