Nutrient-poor foods are those that provide a high number of calories with little to no essential nutrients such as vitamins, minerals, fiber, and protein. These foods often contain high levels of added sugars, unhealthy fats, and sodium, making them less beneficial for overall health compared to nutrient-dense options. Regular consumption of nutrient-poor foods can lead to nutritional deficiencies and contribute to various health issues like obesity, diabetes, and heart disease.