Poor nutrition can also be classified as undernutrition, which is when we are not getting enough nutrition that we require. We require macronutrients and micronutrients to keep our body healthy, such as carbohydrates, fats, proteins, water, vitamins and minerals. These nutrients support our vital body functions including growth, our immune system and our nervous system while preventing diseases. People who are suffering from nutrient deficiencies may not know it until it starts showing up in signs and symptoms.