Why does surgery to reduce obesity sometimes result in malnutrition?

Surgery to reduce obesity, such as bariatric surgery, can lead to malnutrition because it alters the digestive system, reducing the stomach's capacity and bypassing parts of the intestines where nutrient absorption occurs. This can limit the intake of essential nutrients, vitamins, and minerals, making it difficult for patients to meet their nutritional needs. Additionally, patients may struggle with dietary changes post-surgery, leading to inadequate nutrient consumption. Regular monitoring and supplementation are often necessary to prevent malnutrition after such procedures.